MEDICAL 


HUMAN  PHYSIOLOGY, 


STATICAL   AND   DYNAMICAL; 


OB, 


THE    CONDITIONS    AND    COURSE 


OF  THE 


LIFE   Or  MAN. 


JOHH    iLiAM DRAPER,  10.,  LL.D., 

PROFESSOR  OF  CHEMISTRY  AND  PHYSIOLOGY  IN  THE  UNIVERSITY  OF  NEW  YORK; 
AUTHOR  OF  A  "HISTORY  OF  THE  INTELLECTUAL  DEVELOPMENT  OF  EUROPE," 


WITH  NEARLY  300  WOOD  ENGRAVINGS. 


SEVENTH     EDITION. 


NEW    YORK: 

HARPER    &    BROTHERS,    PUBLISHERS, 

FRANKLIN      SQUARE. 

1873. 

R 


Entered,  according  .tq  Ac 


t  of  Congress,  in  the  year  one  thousand  eight  hundred  and 

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:  H  A IWVEy   &  jB  £0  TJJ  ER  §„  . . . 
in  the  Clerk's  Office  of  the  District  Court  of  the  Southern  District  of  New  York. 


PREFACE  TO  THE  SEVENTH  EDITION. 


ANOTHER  edition  of  this  work  being  required,  I  take  the  opportunity 
of  returning  my  thanks  to  the  medical  profession  and  the  public  for 
their  continued  favor. 

A  recent  and  thorough  examination  of  it  enables  me  to  say  that  I  be- 
lieve it  will  be  found  to  present  the  Science  of  Physiology  in  its  most 
modern  form. 

It  is  intended  to  give  an  exposition  of  the  Physiology  of  Man,  con- 
sidered as  an  individual,  and  may  be  looked  upon  in  that  respect  as  a 
work  complete  in  itself. 

But  man  is  also  a  member  of  society,  and,  as  has  been  remarked  in 
previous  editions,  History  is  in  truth  only  a  branch  of  Physiology. 
This  is  the  point  of  view  from  which  I  have  regarded  the  subject  in  my 
"  History  of  the  Intellectual  Development  of  Europe,"  a  work  which, 
taken  together  with  this,  is  intended  as  a  treatise  on  the  entire  range  of 
human  relations,  individual  and  social. 

The  remarkable  favor  with  which  that  portion  of  the  work  has  also 
been  received,  both  in  America  and  Europe,  several  editions,  transla- 
tions, and  reprints  having  been  called  for  in  the  course  of  a  few  months, 
satisfies  me  that  the  views  here  indicated  meet  with  approval. 

For  the  encouragement  so  shown  to  these  works  I  again  return  my 
sincere  thanks. 

New  York,  1865. 


PREFACE  TO  THE  SECOND  EDITION. 


Two  years  ago  the  first  edition  of  this  work  was  published.  Since 
that  time  several  thousand  copies  have  been  disposed  of;  it  has  been  in- 
troduced as  a  text-book  in  many  of  our  medical  schools,  and  has  been 
very  favorably  received  by  the  profession  and  the  public. 

I  have  therefore  felt  it  necessary  to  submit  it  to  a  careful  examination, 
for  the  purpose  of  removing  any  errors  it  may  contain,  and  improving  it 
as  far  as  its  present  form  admits.  The  revision  it  has  undergone  will,  I 
hope,  make  it  worthy  of  the  continued  patronage  of  those  who  have  hith- 
erto shown  it  so  much  encouragement. 

In  these  corrections  I  have  availed  myself  of  many  of  the  suggestions 
made  in  various  reviews  of  the  original  work,  and  take  this  occasion  to 
express  my  thanks  for  the  consideration  shown  toward  it  both  in  Amer- 
ica and  Europe.  JSTo  one  knew  better  than  myself  how  numerous  were 
its  imperfections.  The  manner  in  which  they  have  been  overlooked  has 
served  to  convince  me  that  those  who  were  judges  of  the  science,  and 
could  deal  authoritatively  with  it,  were  disposed  to  encourage  any  at- 
tempt at  its  improvement,  even  though  that  attempt  was  marked  by 
many  conspicuous  shortcomings. 

For  doubtless  they  saw  that  this  book  aimed  at  much  more  than  was 
directly  expressed  upon  its  pages.  To-  treat  Physiology  as  a  branch  of 
Physical  Science  ;  to  exclude  from  it  all  purely  speculative  doctrines  and 
ideas,  the  relics  of  a  philosophy  (if  such  it  can  be  called)  which  flourished 
in  the  Middle  Ages,  though  now  fast  dying  out,  and  from  which  the  more 
advanced  subjects  of  human  knowledge,  such  as  Astronomy  and  Chem- 
istry, have  long  ago  made  themselves  free — to  do  this,  amounts,  in  reality, 
to  a  reorganization  and  reconstruction :  a  task  of  extreme  difficulty,  and 
for  complete  success  demanding  the  conjoint  labors  of  many  philosophers 
and  many  physicians. 

At  the  best,  therefore,  such  an  attempt,  embracing  the  whole  science, 
made  by  a  single  individual,  must  needs  be  unsatisfactory,  if  any  thing 
like  a  rigorous  criticism  be  applied.  And  yet  it  may  be  truly  said  that 
the  interest  of  the  medical  profession  at  the  present  time  requires  that 
such  encouragement  as  this  work  has  received  should  be  extended  to 
every  undertaking  of  the  kind.  I  hope  that  the  success  which  has  in 


VI  PREFACE. 

this  manner  attended  my  labors  may  prove  an  encouragement  to  others 
to  devote  themselves  with  better  results  to  a  similar  task. 

To  physicians  I  would  earnestly  address  myself,  in  the  hope  of  ob- 
taining their  continued  aid  and  hearty  patronage  for  every  such  attempt. 
I  would  ask  them  why  it  is  that  we  never  hear  of  empiricism  in  Natural 
Philosophy,  Engineering,  Astronomy  ?  Is  it  not  because  the  principles 
upon  which  those  subjects  rest  have  ceased  to  be  speculative,  and  are 
restricted  to  the  demonstrative,  the  experimental,  the  practical?  In 
Philosophy,  sects  only  arise  while  principles  are  uncertain ;  in  Medicine, 
the  quack  only  exists  because  there  is  a  doubt.  And  considering  the 
condition  to  which  the  medical  profession  in  our  times  has  come,  consid- 
ering its  decline  in  social  estimation,  and  its  shortcomings  even  in  its 
own  judgment — is  it  not  the  duty  of  every  physician  to  inquire  into  the 
causes  of  such  a  state  ? 

If  a  watch  is  to  be  mended,  or  a  steam-engine  repaired,  do  we  not  ap- 
ply the  principles  of  common  sense  to  the  case  ?  Who  ever  heard  of  sects 
among  watchmakers,  or  quacks  among  engineers  ?  If  we  will  only  apply 
ourselves  in  a  right  spirit  to  its  study,  there  is  nothing  more  mysterious 
or  incomprehensible  in  a  living  organism  than  there  is  in  such  mechanical 
contrivances.  There  is  nothing  in  the  structure  of  man  which  the  intel- 
lect of  man  can  not  understand.  It  is  this,  indeed,  which  constitutes  his 
chief  glory,  and  makes  him  a  worthy  representative  of  the  wisdom  and 
power  of  his  Creator. 

As  in  any  mechanical  contrivance,  so  in  ourselves,  imperfections  and 
disarrangements  can  only  be  repaired  by  a  knowledge  of  the  construction 
of  the  parts,  and  their  manner  of  working.  The  practice  of  Medicine 
must  rest  on  an  exact  Anatomy  and  a  sound  Physiology.  As  soon  as 
it  is  brought  to  this,  empiricism  will  disappear  of  itself;  it  will  need  no 
legal  enactments,  no  ethical  codes  for  its  destruction.  And  for  this  rea- 
son, if  there  were  no  others,  it  is  the  bounden  duty  of  every  physician  to 
encourage  to  the  utmost  within  his  own  sphere  of  influence  every  attempt 
to  realize  such  a  state  of  things.  The  encouragement  which  has  been 
given  to  this  book  I  regard  as  a  token  that  these  principles  are  profound- 
ly recognized  by  the  medical  profession  of  our  country. 

To  students  of  Medicine  I  may  be  permitted,  on  this  occasion,  to  say 
a  few  words.  It  was  chiefly  with  the  hope  of  influencing  them,  and 
guiding  them  into  the  paths  of  scientific  Physiology,  that  I  was  first  in- 
duced to  write  this  book.  I  would  impress  on  them  the  importance  of 
cultivating  habits  of  thought  arising  from  the  exact  and  practical  sci- 
ences. A  great  revolution  is  impending  over  the  profession  to  which 
they  have  devoted  themselves.  If  they  design  to  take  a  leading  posi- 
tion, not  merely  following  it  as  an  industrial  pursuit,  but  regarding  it  as 
one  of  the  most  dignified  and  noble  of  human  occupations,  they  must 


PREFACE.  Vll 

prepare  themselves  in  a  manner  consistent  with  the  modes  of  thought 
that  must  prevail  in  the  times  now  quickly  approaching.  It  may  be  too 
much  for  us  to  expect  that  our  contemporaries,  who  have  been  educated 
in  the  ideas  of  the  past,  should  unlearn  so  much  of  what  they  have  learn- 
ed, should  in  so  many  things  begin  their  studies  again ;  but  we  may  de- 
mand a  right  preparation  from  those  who  are  only  now  commencing. 
In  offering  to  them  this  book,  I  do  not  present  an  untried  work.  It  is 
the  result  of  an  experience  in  teaching  for  many  years,  an  attempt  to  set 
forth  in  plain  language  the  great  features  of  the  science,  and  to  give  in 
sufficient  detail  a  representation  of  the  present  state  of  Physiology.  For 
the  purpose  of  facilitating  its  study,  I  have  divided  the  whole  subject 
into  two  branches,  Statical  and  Dynamical.  The  expediency  of  this  has 
been  impressed  upon  my  attention  by  the  necessity  of  conforming  the 
course  of  lectures  of  which  these  pages  are  an  abstract,  to  the  wants  of 
a  medical  class.  The  physician  is  chiefly  concerned  with  the  conditions 
of  life — the  organic  functions,  as  digestion,  respiration,  secretion,  etc. 
The  doctrines  of  development  and  the  career  of  an  organic  form  are  of 
less  pressing  interest ;  but  it  was  very  soon  found  that  other  advantages 
were  derived  from  this  subdivision,  as  might  have  been  expected  from  its 
conformity  to  the  usages  of  writers  on  other  branches  of  Physical  Science. 

To  the  general  reader  I  may  remark  that  I  have  endeavored  to  carry 
put  in  the  following  pages  the  spirit  of  what  is  contained  in  the  preced- 
ing paragraphs.  I  have  devoted  more  than  twenty  years  not  merely  to 
the  study,  but  also  to  the  experimental  determination  of  physiological 
questions,  of  which  only  a  summary  could  here  be  offered.  It  was  not 
possible  to  give  my  own  results  more  in  detail  in  a  formal  text-book  on 
the  entire  science,  but  it  may  not  perhaps  be  improper  here  to  say  that 
opinions  sometimes  delivered  in  a  few  lines  have  cost  me  many  days,  or 
even  weeks,  of  expensive  and  laborious  experiment. 

Among  the  contemporary  works  I  have  used  as  authorities  are  Dr. 
Carpenter's  different  treatises,  Todd  and  Bowman's  Physiological  Anat- 
omy, and  Kirke's  and  Paget's  Hand-book.  As  respects  monographs,  the 
language  of  the  authors  themselves  has  been  employed  wherever  it  was 
possible.  A  list  of  wood-cuts  is  annexed,  in  which  reference  is  given  to 
the  sources  from  which  those  not  original  have  been  derived.  In  the 
explanation  of  these  engravings  the  description  used  is  that  of  the  au- 
thors themselves  in  most  cases,  and  it  is  incorporated  in  the  text,  as, 
for  instance,  in  Book  I.,  Chapter  XVII.,  in  which,  the  engravings  being 
derived  from  the  Neurology  of  Leveille  and  Hirschfield,  the  accompany- 
ing descriptions  are  merely  translations  from  the  French ;  or,  again,  in 
Book  II.,  Chapter  VII. ,  in  Dr.  Prichard's  statements  of  the  methods  ot 
examining  the  skull.  With  respect  to  the  original  engravings,  it  will  be 
seen  that  many  have  been  obtained  by  the  aid  of  microscopic  photog- 


Vlll  PREFACE. 

raphy,  the  process  having  been  so  far  improved  by  me  as  to  be  made  very 
available  for  these  uses.  For  several  of  the  specimens  from  which  pho- 
tographs have  been  taken  I  am  indebted  to  Mr.  Abbott. 

In  this  work  I  have  therefore  endeavored  to  treat  of  man  according  to 
the  methods  accepted  in  Physical  Science,  but  still  of  man  as  an  individ- 
ual only.  Physiology,  however,  in  its  most  general  acceptation,  has  an- 
other department  connected  with  problems  of  the  highest  interest.  Man 
must  be  studied  not  merely  in  the  individual,  but  also  in  the  race. 
There  is  an  analogy  between  his  advance  from  infancy  through  child- 
hood, youth,  manhood,  to  old  age,  and  his  progress  through  the  stages  of 
civilization.  In  the  whole  range  of  human  study  there  are  no  topics  of 
greater  importance,  or  more  profound,  than  those  dealt  with  in  this  sec- 
ond department  or  division.  It  is  also  capable  of  being  treated  in  the 
same  spirit  and  upon  the  same  principles  as  the  first.  I 'have  nearly 
completed  a  volume,  which  will  serve  as  a  companion  to  this,  in  which 
in  that  manner  the  subject  is  discussed,  and  the  laws  which  preside  over 
the  career  of  nations  established,  and  would  bespeak  for  it  the  considera- 
tion of  the  reader. 

JOHN  W.  DRAPER. 

University,  Neio  York,  July  1st,  1858. 


CONTENTS, 

BOOK    I. 

STATICAL   PHYSIOLOGY. 
CONDITIONS  OF  LIFE. 

CHAPTER  I. 

Conditions  of  Life. — Nature  and  Sources  of  Substances  supplied  to  the  Body. — Annual  Quantities 
required. — Table  of  Physiological  Standards. — Animals  do  not  create,  but  transform  Substan- 
ces.— Properties  and  Quantities  of  Matters  received  by  the  System. — Properties  and  Quantities 
of  those  it  restores. — Heat  of  the  Body  arises  from  Combustion. —  Cooling  Agencies  in  an  An- 
imal.— Necessity  of  Repairs  in  the  System. — Physical  Aspect  of  Man. — The  Soul. — The  Vital 
Principle. — Importance  of  Physical  Science  to  Physiology Page  9 

CHAPTER  U. 
OP  FOOD. 

The  natural  Subdivisions  of  Physiology. — Of  Food:  its  Sources  and  Classification — its  Value  not 
altogether  dependent  on  its  Composition. — Of  Milk:  its  Composition,  and  Use  of  its  Water, 
Casein,  Sugar,  Butter,  and  Salts. —  Variations  in  the  Composition  of  Milk. —  Of  Bread. —  Of 
mixed  Diets. — Of  the  embryonic  Food  of  Birds. — Nutrition  of  carnivorous  and  herbivorous 
Animals. — Food  formed  by  Plants  and  destroyed  by  Animals. —  Uses  of  mixed  Food  and  Cook- 
ing.— Absolute  Amount  of  Food 26 

CHAPTER  III. 

OF  DIGESTION. 
TISSUE-MAKING   OR   HISTOGENETIC   DIGESTION. 

Nature  of  Digestion.— The  Mouth,  Teeth,  Stomach.— The  Salivary  Glands.— Different  Kinds  of 
Saliva. — Properties  of  mixed  Saliva :  its  Quantity,  Composition,  and  Functions. — Relation  of 
the  Salivary  Glands  and  Kidneys. — The  digestive  Tract. — The  Stomach. — Gastric  Juice. — 
Organs  for  its  Preparation. — Manner  of  producing  Chyme. — Influence  of  the  Nerves. — Artifi- 
cial Digestion. — Preparation  and  Properties  of  Pepsin. — Regional  and  functional  Divisions  of 
the  Stomach  in  Animals  and  in  Man. — Object  of  Stomach  Digestion.— Peptones. —  Use  of  Salt. 
— Digestibility  of  various  Articles  of  Food 40 

CHAPTER  IV. 

OF  CALORIFACIENT  OR  INTESTINAL  DIGESTION. 

Nature  of  Intestinal  Digestion. — Structure  of  the  Intestine. — Digestive  Fluids  of  the  Intestine. — 
The  Pancreatic  Juice. —  The  Enteric  Juice. — Juice  of  Lieberkuhn.  —  Secretion  of  Peyer's 
.  Glands. — Bile. — Digestion  of  the  Carbohydrates  and  Hydrocarbons. — Properties  and  Varie- 
ties of  Lactic  Acid. — Doctrine  of  the  Effects  of  Acidity  and  Alkalinity  of  the  Digestive  Juices. 
— Illustration  of  Intestinal  Digestion  from  the  making  of  Wine. — Making  of  Bread. — Influence 
of  Heat  over  Ferments. —  Comparison  of  Gastric  and  Intestinal  Digestion. —  Changes  of  the  In- 
testinal Contents. — The  Fcecal  Residues 67 


X  CONTENTS. 

CHAPTER  V. 
OF  ABSORPTION. 

Double  Mechanism  for  Absorption. — The  Lacteals  and  Veins. — Lacteal  Absorption. — Descrip- 
tion of  a  Vittus. — Analogies  in  Plants. — Introduction  of  Fat  by  the  Villi.  —  The  Chyle. — 
Causes  of  the  Flow  of  Chyle,. — Intermediate  Changes  on  its  Passage  to  the  Blood. — Action  of 
Peyer's  Bodies. — Lymphatic  Absorption. — Nature  of  Lymph.  —  Structure  of  the  Lymphatic 
System.  —  Comparison  of  Chyle,  Lymph,  and  Serum.  —  Function  of  the  Lymphatic  System. — 
Production  of  Fibrin. —  Cutaneous  Absorption. —  Causes  of  the  Flow  of  Lymph. — Apparent  se- 
lecting power  of  the  Absorbents. —  Connection  of  the  Lacteals  and  Lymphatics  with  the  Locomo- 
tive and  Respiratory  Mechanism Page.  84 

CHAPTER  VI. 
ABSORPTION  BY  THE  BLOOD-VESSELS. 

Proof  of  Absorption  by  the  Blood  Capillaries. —  Occurs  as  a  physical  Necessity. — Nature  of  Cap- 
illary Attraction. — Its  Phenomena  in  the  Rise  and  Depression  of  Liquids. —  Conditions  for 
producing  a  Flow  in  a  Capillary  Tube. — Passage  of  Liquids  through  minute  Pores. — General 
Propositions  respecting  Capillary  Attraction. — Endosmosis  and  Exosmosis. — They  depend  on 
Capillary  Attraction. — Force  against  which  these  Movements  may  take  place. — Illustrations  of 
selecting  Power. — General  View  of  the  entire  Function  of  Absorption,  lacteal  and  venous....  102 

CHAPTER  VII. 
OF  THE  BLOOD. 

The  Offices  and  Relation  of  Blood  in  the  System. — The  Plasma  and  Cells. — General  Properties 
and  Composition  of  the  Blood. — Quantity  in  the  Body. —  Coagulation. — Blood-cells. — Their  suc- 
cessive Forms. — The  perfect  Cell. — Hozmatin :  its  Properties. — Number  of  Blood-cells. — Plas- 
ma :  its  Composition,  and  Variations  of  its  Ingredients.— Albumen,  Fibrin,  Fat,  Sugar. — Min- 
eral Ingredients  of  the  Cells  and  Plasma  compared. — Gases  of  the  Blood.— ^Changes  occurring 
during  the  Circulation. — General  Functions  of  the  different  Ingredients  of  the  Blood. — Introduc- 
tion of  Oxygen  by  the  Cells. — Their  transient  Duration Ill 

CHAPTER  Vm. 

OF  THE  CIRCULATION  OF  THE  BLOOD. 

The  Heart  as  a  Machine. — Inadequacy  of  Harvey's  doctrine  of  the  Circulation. — Physical  Prin- 
ciple, of  the  Circulation  ;  applied  in  the  case  of  a  Nucleated  Cell,  Pervious  Tissue,  Motion  of 
Sap  and  of  Blood.  —  Dependence  of  the  Circulation  on  Respiration.  — Forms  of  Circulation : 
Systemic,  Pulmonary,  Portal. — Description  of  the  Heart ;  its  Movements.- —  Their  Force,  Num- 
ber, and  Value. — Sounds  of  the  Heart. —  Cause  of  its  Contractions. — Description  of  the  Arte- 
ries, Capillaries,  Veins. — Explanation  of  the  Circulation  of  the  Blood. — Facts  supporting  it. — 
The  First  Breath , 129 

CHAPTER  DL 
OF  RESPIRATION. 

Respiration  introduces  and  removes  aerial  Substances. —  Coalescence  of  Respiratory  and  Urinary 
Organs  in  Fishes. — Physical  and  chemical  Conditions  of  Respiration. — Interstitial  Movements 
of  Solids,  Liquids,  and  Gases. — Condition  of  Equilibrium  in  the  Diffusion  of  Gases. —  Con- 
densing Action  of  Membranes. — Forms  of  Respiratory  Mechanism. — The  Lungs  of  Man. — 
Three  Stages  in  the  Introduction  of  Air :  Atmospheric  Pressure,  Diffusion  of  Gases,  and 
Condensation  by  Membranes. — Exchange  of  Carbonic  Acid  for  Oxygen. — Divisions  oftheCon- 

.  tents  of  the  Lungs. —  Variations  in  the  expired  Air. — Removal  of  Water. — Effect  ofirrespira- 
bk  Gases. — Experiments  qfRegnault  and  Reiset. — Nervous  Influence  concerned  in  Respiration. 
— Results  of  Respiration 149 


CONTENTS.  xi 


CHAPTER  X. 

OF   ANIMAL   HEAT. 

Participation  of  Organic  Forms  in  external  Variations  of  Temperature. — Mechanism  for  counter- 
balancing these  Variations. — Development  of  Heat  in  Plants  at  Germination  and  Inflorescence. 
— Its  Cause  is  Oxidation. —  Connection  of  Respiration  and  Heat. — Temperature  of  Man. — His 
Power  of  Resistance. — The  diurnal  Variations  of  Heat. —  Connection  of  these  Variations  with 
organic  Periodicities. — Annual  Variations  of  Heat. —  Control  over  them  by  Food,  Clothing,  and 
Shelter. — Source  of  Animal  Heat. — Effect  of  Variations  in  the  Food  and  in  the  respired  Me- 
dium, both  as  respects  its  future  and  Rarefaction. — Hibernation. — Starvation. — Artificial  Re- 
duction of  Temperature  by  Blood-letting. — Principles  of  Reduction  of  Temperature. — Radia- 
tion.—  Contact. — Evaporation. — Their  Balance  with  the  Heating  Processes. — Local  Varia- 
tions eliminated  by  the  Circulation. —  Control  by  the  Nervous  System. — Its  physical  Nature. — 
Allotropism  of  Organic  Bodies Page  175 

CHAPTER  XL 

OF  SECRETION. 
SEROUS,  MUCOUS,  AND   HEPATIC    SECRETIONS. 

Object  of  Secretion. — Type  of  secreting  Mechanism. — Filtration  and  Cell  Action. — Of  Serous 
Membranes  and  their  Secretions. — Of  Mucous  Membranes  and  their  Secretions. — Of  Hepatic  Se- 
cretions.— The  Liver:  its  Development  and  Structure. — Source,  Quantity,  Composition,  Uses, 
and  Flow  of  the  Bile. — Existence  of  biliary  Ingredients  in  the  Blood. — Production  of  Sugar  and 
Fat  in  the  Liver. —  Changes  of  the  Blood-cells  in  it. — General  Summary  of  the  four-fold  Action 
of  the  Liver:  it  produces  Sugar  and  Fat,  eliminates  Bile,  is  the  Seat  of  the  final  Destruction 
of  old  Blood-cells,  and  of  the  Completion  of  new  Ones. — Of  the  ductless  Glands. — The  Spleen: 
its  Functions 189 

CHAPTER  XII. 

OF  EXCRETION. 
THE  URINE,  MILK,  AND  CUTANEOUS  EXCRETIONS. 

Secretion  and  Excretion. 

Of  the  Kidney:  its  Structure  and  Functions. — The  Malpighian  Circulation. — The  Urine:  its  In- 
gredients, their  Variations  and  Sources. — Abnormal  Substances  in  it. —  The  Water  and  Salts 
exude  by  Filtration. —  The  Cells  remove  unoxidized  Bodies. — Manner  of  Removal  of  the  Liquid 
from  the  Malpighian  Sac. 

Of  the  Mammary  Gland:  its  Structure. —  Colostrum  and  Milk. — Ingredients  of  Milk  and  their 
Variations. — Influence  of  Diet. — Inquiry  into  the  Origin  of  the  Ingredients  of  the  Milk,  its  Fat, 
Casein,  Salts,  Sugar. — Manner  of  Action  of  the  Gland  by  Strainage. 

Of  the  Skin. — Structure  of  its  Epiderma  and  Derma. — -Sudoriparous  and  Sebaceous  Glands. — 
Nails.— Hair. — Ingredients  of  Perspiration. — Exhalation:  its  Amount. —  Causes  of  the  Vari- 
able, Action  of  the  Skin. — Its  Double  Action. — Absorption  by  the  Skin. — General  Summary  of 
the  Cutaneous  Functions 213 

CHAPTER  XHI. 

OF  DECAY  AND  NUTRITION. 

Of  Decay :  Loss  of  Weight  in  Starvation. — Interstitial  Death. — Effect  of  Allotropism. 

Of  Nutrition:  Nutrition  for  Repair  and  Nutrition  for  Remodeling,  illustrated  in  the  cases  of  Fat 
and  Bone  respectively. 

Of  Fat:  Its  Peculiarities,  modes  of  Occurrence,  and  Origin. — Inquiry  whether  Animals  ever  form 
Fat. — Artificial  Production  of  it. — Animals  both  collect  it  and  make  it. — Accumulation  of  it 
expends  Nitrogenized  Tissue. —  Conditions  of  the  Fattening  of  Animals.  —  Summary  of  the 
Sources,  Deposit,  and  manner  of  Removal  of  Fat. — Its  partial  Oxidations. — Summary  of  its 
Uses. — Nitrogenized  Nutrition. 


Xll  CONTENTS. 

Of  Bone:  The  Skeleton.  —  Structure  and  Chemical  Composition  of  Bone.  —  Sources  of  its  Con- 
stituents.— The  Process  of  Ossification. — Experiments  on  the  Growth  of  Bone. — Influence  of 
Physical  Agents  on  Development  and  Nutrition Page  243 

CHAPTER  XIV. 

OF  THE  NERVOUS  SYSTEM. 

Divisions  of  the  Nervous  System. —  Cerebro-spinal  and  Sympathetic. — Fibrous  and  Vesicular. 

Structure  and  Functions  of  Nerve  Fibres. —  Centripetal  and  Centrifugal.— Rate  of  Conductibility. 

Anatomical  Examination  of 'the  Structure  and  Functions  of  Nerve  Vesicles. — They  diffuse  Influ- 
ences, are  Magazines  of  Force. — Element  of  Time  introduced  by  Registering  Ganglia. — Oxida- 
tion necessary  to  Nerve  Activity. — Necessity  of  Repair  and  Rest. — Electrical  Examination  of 
the  Functions  of  Vesicles. — Anatomical  and  Electrical  Examinations  agree. 

Automatic  Nerve  Arc. —  Cellated  Nerve  Arc. — Multiple  Arcs. — Commissures. — Registering  Nerve 
Arcs. — Sensorium. — Influential  Arc. 

Suggestions  derived  from  cerebral  Structure  respecting  the  Soul. — Its  independent  Existence  and 
Immortality. 

Ideas  of  Time  and  Space. — Objective,  subjemive,  and  impersonal  Operations. —  Vestiges  of  Im- 
pressions and  their  Interpretation. — Finite  Nature  of  Knowledge. — Mental  Emotions 258 

CHAPTER  XV. 

THE    SPINAL  AXIS. 

Primitive  Development  of  Nervous  System. — Itsflnal  Condition  in  different  Vertebrates. 

The  Spinal  Cord:  its  Structure. — Its  Membranes. — Its  Thirty-one  Pairs  of  Nerves. — Proper- 
ties of  their  Roots. — Functions  of  the  Cord. — BeWs  Discovery. — Transmission  of  Longitudinal 
and  Transverse  Influences. — Reflex  Action  of  the  Cord. — Nature  of  Reflex  Action. — Motor  and 
Sensory  Tracts  of  the  Cord. — Summary  of  its  Functions. 

The  Medulla  Oblongata :  its  Structure  and  Functions. 

The  Pons  Varolii :  its  Structure  and  Functions. 

Dr.  Carpenter's  Views  of  the  Analogy  between  the  Spinal  Cord  of  Vertebrates  and  the  Ventral 
Cord  of  Articulates 291 

CHAPTER  XVI. 

OF  THE  BRAIN. 

The  Brain:  its  Structure. — Its  Motor  and  Sensory  Parts,  Hemispheres,  and  Commissures. — 
The  Sensorium. —  Variations  of  the  Hemispheres  in  Size  and  Weight. — Instrumental  Nature 
of  Cerebrum. —  The  Cerebellum :  its  Structure  and  Functions. — Co-ordinates  muscular  Motions. 
—  Connection  with  Amativeness. — Phrenology. —  Conditions  of  Action  of  Brain. 
Symmetrical  Doubleness  of  the  Brain.— Function  of  each  Half,  and  of  both  conjointly. — Independ- 
ence and  Insubordination  of  each  Hemisphere. — Double  Thought. — Alternate  Thought. — Senti- 
of  Pre-existence. — Loss  of  Perception  of  Time 313 


CHAPTER  XVII. 

OF  THE  CRANIAL  NERVES  AND  THE  GREAT  SYMPATHETIC. 

Enumeration  of  the  Cranial  Nerves. — The  Third  Pair,  or  Oculo-motor. —  The  Fourth  Pair,  orPa- 
thetici. — The  Fifth  Pair,  or  Trigemini. — The  Sixth  Pair,  or  Abducentes. — Illustrations  of  the 
Third,  Fourth,  Fifth,  and  Sixth  Pairs.— The  Seventh  Pair,  or  Facial— Illustration  of  the 
Facial. — The  Ninth  Pair,  or  Glosso-pharyngeal. — Illustration  of  the  Glosso-pharyngeal. — The 
Tenth  Pair,  or  Pneumogastric. — Illustration  of  the  Pneumogastric. — Illustration  of  the  Laryn- 
geals. — The  Eleventh  Pair,  or  Spinal  Accessory. —  The  Twelfth  Pair,  or  Hypoglossal. — Il- 
lustration of  the  Hypoglossal. 

The  Phrenic  Nerve. 

Of  the  Great  Sympathetic  System. — Position,  Structure,  and  Origin  of  the  Sympathetic. — Its  Re- 
lation with  the  Pneumogastric. — Its  Connection  with  the  Spinal  System. — Its  Plexuses. — Its 


CONTENTS.  Xlil 

Ganglia. — They  are  Reservoirs  of  Force. — Summary  of  the  Functions  of  the  Sympathetic. — 
Illustration  of  the  Sympathetic. —  The  Abdominal  Plexuses. — 'The  Solar  Plexus. — TheMesen- 
teric  Plexuses Page  333 

CHAPTER  XVHI. 

OF  THE  VOICE. 

Origin  of  the  Voice. —  Comparative  Physiology  of  Noise,  Song,  Voice. — Distinction  between  Song 
and  Speech. —  The  Larynx,  and  its  Action  in  Singing. — Mutter's  Explanation  of  the  Action  of 
the  Vocal  Organs. — Speaking  Animals  and  Machines. 
Nature  of  Words  and  their  constituent  Sounds. —  Vowels  and  Consonants. —  Whispering. —  Use 

of  the  Voice  of  Animals. 

Of  Languages:  their  Duration,  Character,  History. — Registry  of  Sounds  by  Writing  and  Print- 
ing.— Musical  Signs. — Alphabetic  Writing 351 

CHAPTER  XIX. 

OF  HEARING. 

The  Senses :  General  Remarks  upon. — Five  Organs  of  Sense. — Necessity  of  Apparatus  for  the 
Appreciation  of  Time,  Space,  Pressure,  Temperature,  and  Chemical  Qualities. 

Of  Hearing. — General  Structure  of  the  Organ  of  Hearing. — Physical  Peculiarities  of  Sounds,  In- 
tensity, Time  of  Vibration,  and  Quality. —  The  Tympanum,  Cochlea,  and  Semicircular  Canals 
are  for  the  Appreciation  of  these  peculiarities. 

Structure  and  Functions  of  the  Tympanum,  or  Measurement  of  Intensity. 

Structure  of  the  Cochlea,  its  Spiral  Lamina  and  Scalar. — Measures  the  Time  of  Vibration. — Ac- 
complishment of  Interference  in  the  Scalce. —  Comparative  Anatomy  of  the  Cochlea. 

Structure  of  the  Semicircular  Canals. —  They  estimate  the  Quality  of  Sounds. 

Comparative  Anatomy  of  the  Auditory  Mechanism. — Its  Progress  in  Development. — Imperfection 
of  the  Doctrine  of  Means  and  Ends 359 

CHAPTER  XX. 

OF  VISION. 

Analogy  between  Sound  and  Light. —  Comparative  Anatomy  of  Vision. — Perception  of  Warmth. 
— Structure  of  Ocelli. —  Use  of  Lenses. — Physical  Principle  of  the  Organ  of  Vision. 

Description  of  the  Human  Eye. — Optical  Action  of  its  Parts. — Spherical  and  Chromatic  Aberra- 
tion.— Receiving  Screen  of  the  Eye  is  the  black  Pigment. — Long  and  short  Sight,  and  their 
Correction. — Limits  of  Vision  are  included  in  one  Octave. — Limit  in  estimating  the  Brightness 
of  Light. 

Nervous  Mechanism  of  the  Eye :  its  Structure  and  Functions. — Manner  of  Perception  by  the 
Retina. — The  black  Pigment  absorbs  the  Rays. — Single  and  double  Vision. — Duration  of  Im- 
pressions.— Ocular  Spectra. — Erect  Vision. — Idea  of  the  Solidity  of  Bodies. — Hypothesis  of 
the  Action  of  the  Retina. 

Accessory  Apparatus  of  the  Eye. — The  Eyebrows. — Eyelids. — Lachrymal  Apparatus. — Muscles 
of  the  Ball 379 

CHAPTER  XXI. 
OF  CEREBRAL  SIGHT  OR  INVERSE  VISION. 

Difference  between  ordinary  Vision  and  cerebral  Sight. — Inverse  Vision  depends  on  the  Vestiges 
of  Impressions  existing  in  the  Brain. 

Condition  of  our  perceiving  these  Impressions  is  that  they  must  be  equal  in  Intensity  to  present 
Sensations. —  Two  Methods  of  accomplishing  this  Equalization :  1st,  by  re-enforcing  the  old  Im- 
pressions;  2d,  by  diminishing  the  present  Sensations. 

Emergence  of  old  Impressions  in  Sleep,  Fever,  Death. — Artificial  Emergence  of  such  Vestiges  by 
Protoxide  of  Nitrogen,  Opium,  etc. 

Cerebral  Sight  used  teleologically  to  indicate  the  Immortality  of  the  Soul. 401 


CONTENTS. 


CHAPTER  XXII. 

OF  TOUCH,  AND  THE  DETERMINATION  OF  PRESSURES  AND  TEMPERATURES. 
Functions  of  the  tactile  Mechanism :  its  Structure. — Regions  of  different  Sensitiveness. —  Compar- 
ative Physiology  of  Touch. — Estimate  of  physical  Qualities. 
Perception  of  Temperature. — Subjective  Sensations  of  Temperature Page  417 

CHAPTER  XXHL 

OF  SMELLING,  AND  THE  MEANS    OF  DISTINGUISHING   GASEOUS   AND  VAPOROUS   SUB- 
STANCES. 

Structure  of  the  Organ  of  Smell. — Its  proper  Instrument  the  First  Pair  of  Nerves. — Limited  Re- 
gion of  Smell. —  Conditions  of  its  perfect  Action. — Duration  of  Odors. — Their  localization. — 
Subjective  Odors 423 

CHAPTER  XXTV. 
OF  TASTE. 

Conditions  for  Taste. — Structure  and  Functions  of  the  Tongue. —  Tactile  and  Gustative  Regions 
of  the  Tongue. —  Complementary  Tastes. — Subjective  Tastes 427 

CHAPTER  XXV. 

OF   ANIMAL  MOTION. 

Ciliary  and  Muscular  Motion. — Description  of  Cilia  and  the  Manner  of  Action. 

Muscular  Fibre :  its  Forms,  Non-striated  and  Striated. — Muscle  Juice. — Manner  of  Contraction 
of  a  Muscle :  its  supply  of  Blood-vessels  and  Nerves. — Its  Chemical  Change  during  Activity. — 
Its  Rise  of  Temperature. — Effect  of  Electrical  Currents. — Duration  of  Contractility. 

Doctrine  that  Muscle  Contraction  is  the  result  of  Muscle  Disintegration. — Manner  in  which  ordi- 
nary Cohesion  is  brought  into  play. — Manner  of  Restoration. — Removal  of  the  Heat  and  Oxi- 
dized Bodies. 

Rigor  Mortis. —  Connection  of  Muscle  for  Locomotion. —  Of  Standing. —  Walking. — Running.  431 


BOOK  II. 

DYNAMICAL  PHYSIOLOGY. 
COURSE  OF  LIFE. 

CHAPTER  I. 
OF  THE  PRINCIPLE  OF  ORGANIZATION,  OR  PLASTIC  POWER. 

Remarks  on  the  Subdivision  of  Physiology. 

Career  of  an  Organic  Form. — Three  Modes  of  Development. 

Inquiry  respecting  the  special  Principle  of  Organization. — Illustration  from  the  Growth  of  a  Plant 

in  Darkness  and  Light. — Inference  respecting  Plastic  Power :  its  Nature  and  Properties. — 

Of  the  ordinary  Growth  of  a  Plant,  and  the  Sources  from  which  its  Materials  are  derived. 
Relation  of  all  Organisms  to  each  other. 
Correction  of  the  Doctrine  of  a  Plastic  Power,  from  Considerations  regarding  the  Individuality 

of  a  Plant.— Plants  are  Operations,  not  Individuals.— Physical  Illustration  of  this  View. 
Conclusion  respecting  the  Nature  of  the  Plastic  Power:  that  it  is  a  continued  Manifestation  of  an 

antecedent  physical  Impression ^56 


CONTENTS.  XV 


CHAPTER  H. 
OF  THE  INFLUENCE  OF  PHYSICAL  AGENTS  ON  THE  ORGANIC  SERIES. 

Of  the  Geography  of  Plants:  their  horizontal  and  vertical  Localization. — Influence  of  Heat  on  or- 
ganic Distribution :  isotheral  and  isochimenal  Conditions. — Effects  of  Variations  in  the  Dens- 
ity of  the  Air,  Moisture,  Soil,  Sunlight,  Length  of  Day. — Definite  Quantity  of  Heat  required 
by  Plants. 

Secular  Perturbations  in  the  Species  of  Plants. — Long  Periods  of  Time  required. — Secular  geo- 
logical Changes. 

Inverse  Problem  of  the  Investigation  of  the  Earth's  History  from  her  fossil  Flora. —  Two  great 
terrestrial  Epochs :  Change  in  the  Constitution  of  the  Air,  and  Localization  of  Organisms 
through  Decline  of  the  Earth's  Interior  Heat. 

Difference  between  abrupt  and  gradual  Impressions. — Invariable  Causes  may  produce  abrupt 
Crises. 

Extension  of  the  above  Principles  to  the  Case  of  Animals. —  Case  of  the  Inca  Indians. 

General  Argument  supported  by  the  Extinction  of  Forms. — Development  is  under  the  Influence  of 
Law. — Rudimentary  Organs  and  Excesses  of  Development. — The  Idea  of  Development  by 
Law  consistent  with  natural  Facts Page  472 

CHAPTER  HI. 

OF  THE   ORGANIC  CELL :   ITS   DEVELOPMENT.  REPRODUCTION,  AND  DIFFERENTIATION 
OF  STRUCTURE  AND  FUNCTION. 

Simple  and  Nucleated  Cells.— The  Simple  Cell:  its  Parts  and  Functions.— The  Nucleated  Cell: 
its  Parts  and  Functions. — Activity  of  the  Nucleus. — Other  Forms  of  Cells. —  Cells  arise  by 
Self-origination  and  Reproduction. — Reproduction  by  Subdivision  and  Endogenously. 

The  Animal  Cell. — Forms  of  Cellular  Tissue. — Forms  of  Vascular  Tissue. — Spiral  Vessels, 
Ducts,  etc. 

Differentiation  of  Cells. — Acquisition  of  new  Functions. — Differentiation  of  the  Animal  Cell. — 
Depends  on  Physical  Causes. — Influence  of  Heat  and  Air. — Epoch  of  Differentiation....  492 

CHAPTER  IV. 
OF  REPRODUCTION  AND  DEVELOPMENT. 

Relation  of  Organic  Beings :  they  come  from  a  similar  Cell  and  develop  to  different  Points. — 
Their  Division  by  Classification  is  fictitious. — Development  and  Differentiation. — Homogenesis 
and  Heterogenesis. — They  depend  on  physical  Conditions. — The  reproductive  State  closes  De- 
velopment. 

Development  is  from  the  General  to  the  Special. — Law  of  Von  Bar. — Invariable  Sequence  in 
Differentiation. 

OF  REPRODUCTION:  1st.  By  Generation. —  Conjugation  and  Filaments. — The  Sperm-cell:  its 
Production. — Spermatozoa. — The  Germ-cell:  its  Production. 

Ovum  in  the  Ovary. — Its  Structure. —  Corpus  Luteum. 

Ovum  in  the  Oviduct. — Mulberry  Mass. — Germinal  Membrane. —  The  Chorion. 

Ovum  in  the  Uterus. — Membrana  Decidua. — Placenta. — Development  of  the  Embryo. — Types 
of  Nutrition. — Of  Conception. — Of  Gestation. — Of  Parturition. — Influence  of  both  Parents. 

2d.  By  Gemmation. — Budding  of  Plants  and  Animals. — Of  Grafting. — Limit  of  Gemmation. — 
Influence  of  Temperature  on  Gemmation. 

Alternations  of  Generation. — Its  Explanation 505 

CHAPTER  V. 

THE  GROWTH  OF  MAN. 

Infancy. —  Weight  and  Size  of  the  Infant. —  Weight  and  Size  at  subsequent  Periods. — Develop- 
ment of  the  Intellect. — Maturity  of  Man. —  Tendency  to  Crime. — Maxima  of  Physical  and  Men- 
tal Strength. 


XVI  CONTENTS. 

Mental  and  Physical  Decline. — Mortality  at  different  Periods  of  Life. —  Comparative  Structure, 

Functions,  and  Mortality  of  the  two  Sexes. 
Artificial  Epochs  of  Life. — Gradual  Change  in  the  Mental  Qualities. — Independent  Existence  of 

the  Soul. '. Page  538 

CHAPTER  VI. 

OF  SLEEP  AND  DEATH. 

Causes  of  the  Necessity  for  Sleep. — Its  Duration  and  Manner  of  Approach. — Manner  of  Awak- 
ing.—  Cause  of  Night-sleep. — Increased  Warmth  required. —  Connection  of  Sleep  and  Food. 

Of  Dreams:  their  Origin  and  Phenomena. — Somnambulism. — Nightmare. 

Of  Death. — Old  Age. — Internal  Causes  of  Decline. — Death  by  Accident  and  by  Old  Age. — The 
Hippocratic  Face. — Final  Insensibility 551 

CHAPTER  VII. 

ON  THE  INFLUENCE  OF  PHYSICAL  AGENTS  ON  THE  ASPECT  AND  FORM  OF  MAN  AND 
ON  HIS  INTELLECTUAL  QUALITIES. 

Differences  in  Form,  Habits,  and  Color  of  Men. — Ideal  Type  of  Man. — Its  Ascent  and  Descent. 
—  Causes  of  these  Variations. 

Doctrine  of  the  Unity  of  the  Human  Race. — Doctrine  of  its  Origin  from  many  Centres. 

Influence  of  Heat  on  Complexion. —  Cause  of  Climate  Variations. — Influence  of  Heat  illustrated 
by  the  cases  of  the  Indo-Europeans,  the  Mongols,  the  American  Indians,  and  the  Africans. — 
Distribution  of  Complexion  in  the  Tropical  Races. 

Variations  in  the  Skeleton. — Four  Modes  of  examining  the  Skull. —  Connection  of  the  Shape  of 
the  Skull  and  Manner  of  Life. — Physical  Causes  of  Variation  of  the  Skull. 

Influence  of  the  Action  of  the  Liver  on  Complexion. — Influence  of  the  Action  of  the  Liver  on  the 
Form  of  the  Skull. — Base  Form  of  Skull  arising  from  Low  as  well  as  High  Temperatures. — 
Disappearance  of  the  Red-haired  and  Blue-eyed  Men  in  Europe. 

The  Intellectual  Qualities  of  Nations. — Synthetical  Mind  of  the  Asiatic. — Analytical  Mind  of  the 
European. — Their  respective  Contributions  to  Human  Civilization. — Spread  of  Mohammedan- 
ism in  Africa. — Spread  of  Christianity  in  America. — Manner  of  the  Progress  of  all  Nations 
in  Civilization 563 

CHAPTER  VIH. 
SOCIAL  MECHANICS. 

Comparative  Sociology. —  Connection  of  Structure  and  Habit. —  Connection  of  History  and  Phys- 
iology.—  Insect  Society. — Descartes' 's  Doctrine  that  Insects  are  Automata. — Necessity  of  a 
Mechanism  of  Registry  for  Instinct,  Reason,  and  Civilization. 

Nature  of  Man. — Influence  of  surrounding  Circumstances  on  him. — Dejiniteness  of  his  Career. 

GENERAL  FACTS  OP  EUROPEAN  HISTORY. — Introduction  of  Egyptian  Civilization  into  Europe. — 
The  Registry  of  Facts  by  Writing. — Egyptian  Philosophy  in  the  Greek  Schools. — The  Persian 
Empire:  its  Influence. — Analytical  Quality  of  the  European  Mind. — Influence  of  the  Greek 
Schools  on  modern  Philosophy. 

Origin  of  European  Commerce. — Discovery  of  the  Straits  of  Gibraltar. — Macedonian  Campaign. 
— Reconstruction  of  Monarchy  in  Egypt. 

The  Roman  Empire :  its  centralizing  and  civilizing  Power. — Fall  of  European  Paganism. — In- 
fluence of  the  Christian  Church.— The  Sabbath  Day.— The  Reformation. 

Influence  of  Mohammedanism  on  Europe. —  The  Arab  physical  Science. — The  Crusades. — Dis- 
covery of  America  by  the  Spaniards. — Fall  of  the  Spanish  Power. 

Later  Mental  Changes  in  Europe. — Disappearance  of  Credulity. — Physiological  Change  of  Eu- 
ropeans.— Effect  of  Mohammedanism  in  changing  the  Centre  of  Intellect  of  Europe. — Analyt- 
ical Tendency  of  the  European  Mind. — Advantages  resulting  therefrom 602 


LIST  OF  ILLUSTRATIONS. 


l!  The  lower  Jaw Wilson 41 

2.  Section  of  Stomach Author 42 

3.  Digestive  Tract Harrison 48 

4.  Mucous  Membrane  of  Stomach Wilson 50 

5.  Stomach  Follicles  and  Tubes Todd  and  Bowman 50 

6.  Section  of  Stomach  Tubes "  "       51 

7.  The  Hydra 51 

8.  Digestive  Tract  of  Beetle Milne  Edwards 58 

9.  Mucous  Membrane  of  Beetle's  Stomach Photograph  by  Author 58 

10.  Digestive  Tract  of  Fowl "  "      58 

11.  Stomach  of  African  Ostrich Cuvier 59 


of  Dormouse "  59 

ofCapeHyrax "  59 

ofPorqppine "  59 

ofPorpoise "  59 

ofKangaroo "  59 


12. 
13. 
14. 
15. 
16. 

17.  of  a  Ruminant "      59 

18.  Posterior  View  of  human  Stomach Retzius 61 

19.  Posterior  View  of  Duodenum Bourgery 68 

20.  Diagram  of  Brunner's  Glands Author 69 

21.  Diagram  of  Follicles  of  Lieberkuhn "      69 

22.  Peyerian  Glands Thomson 70 

23.  Section  of  Heum  Wall Kolliker 85 

24.  Villi  of  Monkey Camera  Lucida  by  Author 85 

25.  Villi  of  Duodenum Author 85 

26.  ViUi  of  Jejunum "      85 

27.  Section  of  Villi "      86 

28.  Villi  of  Squirrel "       88 

29.  Principle  of  Venturi "       90 

30.  Thoracic  Duct Wilson 90 

31.  Chyle  Corpuscles  with  Blood-cells Photograph  by  Author 93 

32.  "  "  "    Water Author 94 

33.  "  "  "    Acetic  Acid "      94 

34.  Lymphatics  of  large  Intestine Bourgery 97 

35.  Diagram  of  Lymph  Gland Goodsir 97 

36.  Evolution  of  Lymph  Cells " 97 

37.  Capillary"  Depression  of  a  Liquid Author 104 

38.  Capillary  Elevation  of  a  Liquid "      104 

39.  Passage  of  Water  through  a  Crevice "       105 

40.  Endosmometer "      106 

41.  Selecting  Power  of  a  Membrane "      108 

42.  Human  Blood-cells Photograph  by  Author 116 

43.  Elliptic  Blood-cells "  "      116 

44.  Action  of  Water  on  elliptic  Cells "  "      116 

45.  Action  of  Acetic  Acid "  "      117 

>  46.  Reptile  Blood-cells "  «       117 

47.  Human  Blood-crystals Lehmann 119 

A 


LIST  OF  ILLUSTKATTONS. 


PAS! 


48.  Blood-crystals  of  Guinea-pig Lehmann 119 

49.  Blood-crystals  of  Squirrel "         120 

50.  Stellated  Blood-cells Photograph  by  Author 127 

61.  Capillary  Motion Author 131 

52.  Motion  in  Cells "       132 

53.  Circulation  in  Tradescantia "       132 

54.  Diagram  of  Fish  Circulation Milne  Edwards.... 135 

55.  Rudimentary  Heart Thomson 135 

56.  Diagram  of  single  Heart Roget 136 

67.  Heart  of  Dugong Home 136 

58.  Human  Heart  on  right  Side Wilson 136 

59.  Human  Heart  on  left  Side "      137 

60.  Muscular  Fibres  of  Heart ...Author 137 

61.  Vessels  of  Mucous  Membrane  of  Stomach "      142 

62.  Vessels  of  Villi  of  Duodenum " 142 

63.  Capillary  Circulation  of  Frog's  Foot Wagner 142 

64.  White  Corpuscles  in  the  still  Layer "       143 

65.  Valves  of  Veins  open Roget  143 

66.  Valves  of  Veins  shut "      143 

67.  Diffusion  of  Gases Author 152 

68.  Diffusion  through  Earthenware " 152 

69.  Diffusion  through  India-rubber "      153 

70.  Passage  through  Films "     * 153 

71.  Force  of  Filtration "      155 

72.  Air  Vesicles  of  Insect Fabricius 157 

73.  Spiracle  of  Insect Photograph  by  Author 157 

74.  Air  Sac  of  Fish Blasius 157 

75.  Lung  of  Reptile Flourens 158 

76.  Lungs  of  Frog "         159 

77.  Human  Air-tubes Wagner 160 

78.  Heart  and  Lungs " 160 

79.  Capillaries  on  Lungs Rathke 160 

80.  Mechanism  of  Respiration Author 161 

81.  Experiments  on  Respiration Regnault  and  Reiset 170 

82.  Hepatic  Coecum  of  Cray-fish Leidy 198 

83.  Bile-ducts  entering  the  Duodenum Paxton 199 

84.  Hepatic  Veins  in  the  Lobules  of  the  Liver Kiernan 199 

85.  Origin  of  Hepatic  Veins "       200 

86.  Origin  of  Bile-ducts "       200 

87.  Hepatic  Cells "       201 

88.  Section  of  Kidney .....Wilson 215 

89.  Diagram  of  Malpighian  Corpuscle Kolliker 216 

90.  Glomerulus  of  horse "       216 

91.  Cilia  on  Uriniferous  Tube Bowman 216 

92.  Diagram  of  Malpighian  Circulation "       217 

93.  Malpighian  Tuft Isaacs  .' 217 

94.  Ruptured  Malpighian  Coil  of  Deer " 217 

95.  Nucleated  Cells  on  Coil "      217 

96.  Development  of  Mammary  Gland Kolliker 225 

97.  Section  of  human  Mamma 225 

98.  Colostral  Corpuscles Photograph  by  Author 225 

99.  Epidermis  of  Dog "  "     235 

100.  Section  of  Skin Kolliker 235 

101.  Under  Surface  of  Cuticle Todd  and  Bowman 235 

102.  Papillae  of  Palm "  "       235 

103.  Skin  of  Palm ,     «  "       236 


LIST  OF   ILLUSTRATIONS.  3 

104.  Section  of  Hair Todd  and  Bowman 236 

105.  Transverse  Section  of  Hair Photograph  by  Author 237 

106.  Sudoriparous  Gland Wagner 237 

107.  Fat-cell  Schwann 246 

108.  Adipose  and  areolar  Tissue Berres 246 

109.  Transverse  Section  of  Bone Photograph  by  Author 254 

110.  Lucunae  and  Canaliculi Author 254 

111.  Ossifying  Cartilage Kolliker : 255 

112.  Ossifying  Cartilage Photograph  by  Author 256 

113.  Ossifying  Femur Kolliker 256 

114.  Axis  Cylinder Author 261 

115.  Subdivision  of  Nerve  Fibres Kolliker 262 

116.  Nerve-cells "       263 

117.  Bipolar  Nerve-cells "       264 

118.  Multipolar  Nerve-cell Author 264 

119.  Nerve  Cells  and  Tubes Wagner 264 

120.  Nerve  Cells  and  Tubes Purkinje.. 264 

121.  Dorsal  Ganglion  of  Mouse Valentin 267 

122.  Simple  automatic  Arc Author 277 

123.  Simple  cellated  Arc "      v 278 

124.  Multiple  Nerve  Arcs "      278 

125.  Commissured  Arcs " 279 

126.  Nervous  System  of  Larva  of  Sphinx  Ligustri  ....Newport 279 

127.  Nervous  System  of  Pupa  of  Sphinx  Ligustri "        279 

128.  Nervous  System  of  Imago  of  Sphinx  Ligustri....       "        279 

129.  Nervous  System  of  Asterias Tiedemann. 279 

130.  Nervous  System  of  Patella Cuvier 279 

131.  Nervous  System  of  Octopus " 279 

132.  Nervous  System  of  Aplysia "      280 

133.  Registering  Nerve  Arc Author •.  281 

134.  Suppression  of  Centrifugal  Branch....' " 281 

135.  Influential  Arc «« 282 

136.  Primitive  Trace Bischoff 293 

137.  Origin  of  Brain  on  Spinal  Cord "       293 

138.  Spinal  Cord Photograph  from  Leveille 295 

«  «       295 

"  "       296 

"  "      297 

"  "  .    297 

u  n  297 

144.  Portion  of  Cord  of  Spirostreptus Newport : 301 

145.  Front  of  Medulla  Oblongata Photograph  from  Leveille 305 

146.  Back  of  Medulla  Oblongata "  "  "       305 

147.  Interior  of  Medulla  and  Pons "  "  "       305 

148.  Posterior  View  of  Medulla  Oblongata Todd  and  Bowman 306 

149.  Nervous  System  of  Larva  of  Sphinx  Ligustri  ....Newport 308 

150.  Ganglion  of  Polydesmus  Maculatus "       309 

151.  Ganglion  of  Centipede "       312 

152.  Thoracic  Portion  of  Cord  of  Sphinx  Ligustri....       "       313 

153.  Respiratory  and  locomotive  Ganglia " 313 

154.  External  lateral  Face  of  Brain Photograph  from  Leveille 316 

155.  Superior  Aspect  of  Brain "  "  "       316 

156.  Internal  lateral  Face  of  Brain "  "  "       317 

157.  Base  of  Brain Photograph  by  Author 317 

158.  Diagram  of  Brain Mayo 318 

159.  The  Motor  Tract...,  ...Bell...  319 


139.  Section  of  Spinal  Cord 

140.  Spinal  Dura  Mater 

141.  Origin  of  anterior  Roots  of  Nerves 

142.  Origin  of  posterior  Roots , 

143.  Origin  of  both  Roots 


LIST   OF  ILLUSTRATIONS. 


FIG. 

160. 

161. 

162. 

163. 

164. 

165. 

166. 

167. 

168. 

169. 

170. 

171. 

172. 

173. 

174. 

175. 

176. 

177. 

178. 

179. 

180. 

181. 

182. 

183. 

184. 

185. 

186. 

187. 

188. 

189. 

190. 

191. 

192. 

193, 

194. 

195. 

196. 

197. 

198. 

199. 

200. 

201. 

202. 

203. 

204. 

205. 

206. 

207. 

208. 

209. 

210. 

211. 

212. 

213. 

214. 

215. 


PAGE 

The  Sensory  Tract Bell 320 

Nerves  of  the  Orbit Photograph  from  Leveille 334 

Nerves  in  the  Orbital  Cavity «  «  «       335 

Diagram  of  the  Fifth  Nerve "  «  «      335 

335 

..  336 


Ganglion  of  Gasser 

The  Fifth  Nerve 

The  inferior  Maxillary 

The  Facial  Nerve 

The  Glosso-pharyngeal  Nerve. 

Diagram  of  Anastomoses 

The  left  Pneumogastric 

Pulmonary  Ganglia 

The  inferior  Laryngeals......... 

The  Hypoglossal  Nerve......... 

The  Phrenic  Nerve... 


337 

339 

339 

341 

-342 

342 

343 

344 

Relation  of  the  Sympathetic  and  Spinal Todd  and  Bowman 345 

The  Great  Sympathetic Photograph  from  Leveille. 

Abdominal  Plexuses "  "  " 

The  Solar  Plexus "  "  " 

The  Mesenteric  Plexuses "  "  " 

Spiracle  of  Insect : .Photograph  by  Author 

Profile  of  Larynx Leveille 

Posterior  View  of  Larynx "       

External,  middle,  and  internal  Ear "       

Tympanic  Cavity "       

Facial  in  the  Aqueduct  of  Fallopius "       

Interior  of  Cochlea 

Section  of  Cochlea 

Magnified  Section  of  Cochlea 

Cochlear  Nerve 

Auditory  Nerve 

Ossicles  and  their  Muscles 

Tympanic  Face  of  Labyrinth "       

Cranial  Face  of  Labyrinth "       

Interior  of  ^Labyrinth "       

Interior  of  Labyrinth "       

Profile  of  Eye "       , 

Front  View  of  Eye "       

Section  of  Eye ,.       " , 

Veins  of  the  Choroid "       

Arteries  of  the  Choroid "      , 

Yellow  Spot  of  Soemmering Soemmering 

Membrane  of  Jacob Jacob 

Simple  Papillae , Todd  and  Bowman 

Compound  Papillae Kolliker 

Olfactory  Nerve Leveill^ 

Olfactory  Nerve "      

The  Tongue Photograph  from  Leveille, 

Ciliated  Cells Author , 

Ciliated  Animalcule Ehrenberg 

Hydra  walking Trembley , 

Striated  muscular  Fasciculi Photograph  by  Author , 

Human  Sarcolemma Bowman 

Sarcolemma  of  Fish , "        

Ultimate  muscular  Fibre Photograph  by  Author 

Unstriped  muscular  Fibre Author 


,  348 
,  349 
350 
350 
352 
354 
354 
362 
362 
362 
369 
369 
370 
370 
370 
370 
374 
374 
375 
375 
383 
383 
383 
385 
385 
386 
390 
420 
420 
424 
424 
428 
431 
432 
432 
433 
433 
433 
433 
435 


LIST  OF  ILLUSTEATIONS.  5 

216.  Unstriped  Fibres  in  Acetic  Acid Author 435 

217.  Muscle  Cells Kolliker 435 

218.  Muscular  Fasciculi  torn  in  Discs Bowman 436 

219.  Transverse  Section  of  human  Muscle "       437 

220.  Transverse  Section  of  Muscle  of  Teal " 437 

221.  Non-fibrillated  Insect  Fasciculi Photograph  by  Author 437 

222.  Non-fibrillated  Insect  Fasciculi* "  "       437 

223.  Contracting  Muscle  of  Dytiscus Bowman 438 

224.  Sarcolemma  raised  in  BulL» *. Todd  and  Bowman 438 

225.  Fasciculus  contracting "  "        439 

226.  Distribution  of  muscular  Capillaries Berres 439 

227.  Muscular  Arteries  and  Veins Kolliker 440 

228.  Distribution  of  muscular  Nerves Burdach 440 

229.  Volume  of  contracting  Muscle Author 450 

230.  Hasmatococcus  Binalis Hassall -494 

231.  Conferva  glomerata Mohl  495 

232.  Simple  Cellular  Tissue Photograph  by  Author 497 

233.  Muriform  Cellular  Tissue "  "      497 

234.  Fibro-cellular  Tissue "  "      497 

235.  Spiral  Vessels  of  Cactus "       -  "      498 

236.  Spiral  Vessels  of  Banana "  "      498 

237.  Woody  Fibre  of  Pine "  "      498 

238.  Yellow  Fibrous  Tissue ; Author 499 

239.  White  Fibrous  Tissue "      499 

240.  Areolar  Tissue "      499 

241.  Development  of  Frog Rusconi 509 

242.  Frog ; 510 

243.  Development  of  Crab Couch 510 

244.  Development  of  Insects Straus  Durckheim 510 

245.  Zygnema  Quinmum Kiitzing 515 

246.  Testis Arnold 517 

247.  Development  of  Spermatozoa Wagner 518 

248.  Section  of  Ovary Kolliker 521 

249.  Section  of  Graafian  Vesicle Von  Bar 521 

250.  Ovum Barry 521 

251.  Diagram  of  Graafian  Vesicle ..Kirkes  and  Paget 521 

252.  Corpora  Lutea Patterson  and  Montgomery 522 

253.  Ovarian  Ovum 523 

254.  Ovarian  Ovum 523 

255.  Segmentation  of  Ovum Bischoff 524 

256.  Segmentation  of  Ovum Kolliker  andBagg.1 524 

257.  Uterine  Tubes Weber 525 

258.  Layers  of  Germinal  Membrane Bischoff 527 

259.  Primitive  Groove "       527 

260.  Origin  of  Brain "       528 

261.  Production  of  Vessels Wagner 529 

262.  Production  of  Lymphatics Kolliker 529 

263.  Rudimentary  Heart Thomson 529 

264.  Foetal  Heart Von  Bar 530 

265.  Hydra  budding Trembley 534 

266.  Newton Photograph  from  Principia 563 

267.  Australian D'Urville. — Photographed  from  Prichard 563 

268.  Australians D'Urville.—  "  "  «        564 

269.  Brahmin Branwhite.—  "  "  "        573 

270.  Chinese "  «  "        574 

271.  Kamtschatdale...  "  "  "  ..  575 


6  LIST  OF  ILLUSTRATIONS. 

no.  PIOB 

272.  Sac  Indian Catlin.— Photographed  from  Pilchard 575 


273.  Cherokee  Indian Catlin.— 

274.  California  Indian Choris. — 

275.  California  Indians Choris.— 

276.  Abyssinian D'Abbadie. — 


576 

576 

576 

.....  577 

577 

..  578 


277.  Native  of  Madagascar 

278.  Native  of  Mozambique " 

279.  Negro  of  Guinea Author 579 

280.  Philippine  Negro Choris. — Photographed  from  Prichard 579 

281 .  Skeleton  of  Man,  Chimpanzee,  and  Orang Photograph  by  Author 581 

282.  Skull  of  European ....Prichard 582 

283.  Skull  of  Negro "        582 

284.  Skull  of  Chimpanzee "       582 

285.  Skull  of  Orang "       582 

286.  Caucasian  Skull "        583 

287.  Mongol  Skull "        583 

288.  Negro  Skull " 584 

289.  Titicacan  Skull " 584 

290.  Base  of  human  Skull "        584 

291.  Base  of  Orang  Skull "        584 

292.  Esquimaux  Skull "        585 

293.  Negro  Skull.. Author 587 

294.  Trench  Skull "      587 

295.  Cephalic  Ganglia Newport 607 

296.  Thoracic  Portion  of  Ventral  Cord "      607 


HUM  AIT    PHYSIOLOGY, 


STATICAL  AND  DYNAMICAL 


HUMAI  PHYSIOLOGY. 


BOOK    FIRST. 

STATICAL  PHYSIOLOGY, 

CONDITIONS  OF  LIFE. 

CHAPTER  I. 

Conditions  of  Life. — Nature  and  Sources  of  Substances  supplied  to  the  Body. — Annual  Quantities 
required. —  Table  of  Physiological  Standards. — Animals  do  not  create,  but  transform  Substan- 
ces.— Properties  and  Quantities  of  Matters  received  by  the  System. — Properties  and  Quantities 
of  those  it  restores. — Heat  of  the  Body  arises  from  Combustion. —  Cooling  Agencies  in  an  An- 
imal.— Necessity  of  Repairs  in  the  System. — Physical  Aspect  of  Man. — The  SouL — The  Vital 
Principle. — Importance  of  Physical  Science  to  Physiology. 

FOR  the  maintenance  of  the  life  of  man  three  chemical  conditions  must 
be  complied  with.  He  must  be  furnished  with  air,  water,  and  combusti- 
ble matter. 

Under  the  same  conditions,  also,  all  animals  exist.  Even  in  those 
which  seem  to  furnish  us  with  instances  of  departure  from  this  Three  condi- 
general  rule,  the  exceptions  are  rather  apparent  than  real.  To  tions  oflife- 
breathe,  to  drink,  to  eat,  are  the  indispensable  requisites  of  life.  If  there 
be  among  insects  some  which  seem  never  to  take  water,  or  among  fishes 
some  which  never  taste  solid  food,  these  peculiarities  disappear  as  soon 
as  we  understand  them  properly.  Where  a  high  development  has  been 
attained,  as  in  man,  experience  assures  us  that  the  same  inevitable  result 
awaits  a  cessation  of  respiration  for  a  few  moments,  an  abstinence  from 
water  for  a  few  hours,  or  from  food  for  a  few  days. 

The  supply  of  a  part  of  these  necessaries  of  life  is  adjusted  to  the  ur- 
gency of  the  want.  The  act  of  breathing  is  incapable  of  de-  Sources  of  sup- 
lay,  but  the  air  is  accordingly  every  where  present,  and  al-  ply  of  material, 
ways  fit  for  use.  We  can  bear  with  thirst  for  a  little  time,  and  the  earth 
here  and  there  furnishes  her  springs  and  other  stores  of  water.  But  far 
otherwise  is  it  in  the  obtaining  of  food.  It  is  the  lot  of  all  animals  to 
secure  nourishment  by  labor,  and  even  of  men  the  larger  proportion,  both 


10-  EQUILIBRIUM   OF  LIFE. 

in  civilized  and  savage  countries,  submit  to  a  hard  destiny.     To  obtain 
their  daily  bread  is  the  great  object  of  life. 

What  is  the  philosophical  explanation  of  this  necessity  for  a  supply 
of  air,  of  water,  of  food  ?  Why  is  it  that  the  system  will  bear  so  little 
delay  ? 

The  answer  which  Physiology  gives  to  these  questions  is  an  answer 
Life  de  ends  °^  ommous  import,  but  the  whole  science  is  a  commentary  on 
on  destruction  its  truth.  The  condition  of  life  is  death.  No  part  of  a  liv- 
of  material.  ^  mecnanism  can  act  without  wearing  away,  and  for  the 
continuance  of  its  functions  there  is  therefore  an  absolute  necessity  for 
repair. 

It  has  been  greatly  to  the  detriment  of  physiology  and  the  practice  of 
medicine  that  this  conception  has  not  been  thoroughly  realized  until  late 
times.  The  aspect  of  identity  which  an  animal  presents  is  an  illusion, 
hiding  from  us  the  true  state  of  the  case.  It  has  been  the  fruitful  source 
of  errors  which  have  retarded  the  progress  of  these  sciences.  What  could 
their  career  possibly  be  when  men  had  persuaded  themselves  that  a  liv- 
ing being  possesses  a  capacity  for  resisting  any  change,  and  that  organic 
structures  never  yield  to  external  physical  influences  until  after  death  ? 

But  life,  far  from  being  a  condition  of  immobility,  is  a  condition  of 
ceaseless  change.  An  organism,  no  matter  of  what  grade  it  may  be,  is 
only  a  temporary  form,  which  myriads  of  particles,  passing  through  a  de- 
terminate career,  give  rise  to.  It  is  like  the  flame  of  a  lamp,  which  pre- 
sents for  a  long  time  the  same  aspect,  being  ceaselessly  fed  as  it  ceaselessly 
wastes  away.  But  we  never  permit  ourselves  to  be  deceived  by  the  sim- 
ulated unchangeableness  which  such  a  natural  appearance  offers.  We 
recognize  it  as  only  a  form  arising  from  the  course  which  the  disappear- 
ing particles  take.  And  so  it  is  even  with  man.  He  is  fed  with  more 
than  a  ton  weight  of  material  in  a  year,  and  in  the  same  time  wastes  more 
than  a  ton  away. 

There  is,  therefore,  a  general  condition  of  equilibrium  which  every  an- 
Conditions  of  *ma^  PresemX  depending  upon  its  receipts  and  its  wastes,  a 
equilibrium  in  proper  knowledge  of  the  conditions  of  which  is  at  the  founda- 
tion of  Physiology.  That  we  may  approach  this  problem  un- 
der its  simplest  form,  free  it  from  all  unnecessary  complications,  and  make 
it  of  most  interest  to  the  special  object  of  this  book,  the  remarks  now 
to  be  made  will  be  confined  to  our  own  species,  and,  except  when  oth- 
erwise stated,  to  a  condition  of  health,  and  to  the  adult  period  of  life. 

To  have  a  uniform  standard  of  reference,  we  may  assume  one  hundred 
and  forty  pounds  as  the  weight  of  an  adult  healthy  man.  Now  the  con- 
stant consumption  of  food,  water,  and  atmospheric  air  tends  steadily  to 
increase  that  weight,  and  even  in  a  very  short  time  a  disturbance  arising 
from  these  sources  would  be  perceptible,  w^ere  there  not  some  causes  of 


ANNUAL  RECEIPTS   AND  WASTE  IN  MAN.  11 

compensation.  But  even  after  a  year,  if  a  state  of  health  is  maintained, 
the  weight  may  remain  precisely  what  it  was,  and  this  may  continue  year 
after  year  in  succession.  The  consumption  of  large  quantities  of  solid, 
liquid,  and  gaseous  matter  does  not  therefore  necessarily  add  to  the 
weight. 

There  are  two  periods  of  life  for  which  this  observation  will  not  hold 
good.  They  are  infancy  and  old  age.  During  the  former  the  weight  in- 
creases from  day  to  day,  and  during  the  latter  it  slowly  declines. 

If  there  be  thus  causes  for  the  increase  of  weight  of  the  living  system, 
there  are  also  causes  for  its  diminution.  Setting  aside  the  minor  ones, 
these  may  be  chiefly  enumerated  as  loss  by  urine,  by  faeces,  by  transpired 
and  expired  matters.  By  transpired  matters,  are  meant  such  as  escape 
under  the  form  of  liquids  and  gases  from  the  skin,  and  by  expired  mat- 
ters, vapors  and  gases  escaping  from  the  lungs.  There  is,  therefore,  a 
tendency  to  an  increase  and  a  tendency  to  a  diminution  of  the  weight, 
and,  in  the  condition  of  equilibrium  we  are  considering,  these  must  bal- 
ance one  another. 

If  a  man  of  the  standard  weight  abstains  from  the  taking  of  water  and 
food,  a  good  balance  will  prove  that  in  the  course  of  less  than  an  hour  he 
has  become  lighter.  If  he  still  persists,  it  needs  no  instrument  to  detect 
what  is  going  on ;  the  eye  perceives  it,  for  emaciation  ensues. 

How,  then,  is  it  possible  for  a  living  being  to  continue  at  its  standard, 
except  the  causes  of  increase  are  precisely  equal  in  effect  to  the  causes 
of  diminution?  Overlooking  minor  ones,  we  may  therefore  assert  that 
the  sum  total  of  food,  water,  and  atmospheric  air  taken  in  a  given  period 
of  time  is  precisely  equal  to  the  sum  total  of  all  the  losses  by  urine,  fae- 
ces, transpired,  and  expired  matters ;  for  if  the  receipts  were  greater,  the 
weight  must  increase — if  the  losses  were  greater,  the  weight  must  dimin- 
ish. Persistency  in  this  respect  proves  equality,  and  the  case  is  just  as 
simple  as  in  the  common  affairs  of  life ;  he  who  pays  less  than  he  receives 
grows  rich ;  if  his  payments  are  more  than  his  receipts,  he  becomes  poor ; 
but  his  condition  is  unchanged  if  his  payments  and  receipts  are  equal. 
Infancy,  old  age,  and  manhood  answer  to  these  circumstances  respect- 
ively. 

From  the  army  and  navy  diet  scales  of  France  and  England,  which  of 
course  are  based  upon  the  recognized  necessities  of  large  Quantity  of 
numbers  of  men  in  active  life,  it  is  inferred  that  about  2 J 
pounds  avoirdupois  of  dry  food  per  day  are  required  for  each  year, 
individual ;  of  this  about  three  quarters  are  vegetable  and  the  rest  animal. 
At  the  close  of  an  entire  year  the  amount  is  upward  of  800  pounds. 
Enumerating  under  the  title  of  water  all  the  various  drinks — coffee,  tea, 
alcohol,  wine,  &c. — its  estimated  quantity  is  about  1500  pounds  per  an- 
num. That  for  oxygen  may  be  taken  at  800  pounds. 


12  ANNUAL  RECEIPTS  AND  WASTE  IN  MAN. 

With  these  figures  before  us,  we  are  able  to  see  how  the  case  stands. 
The  food,  water,  and  air  which  a  man  receives  amount  in  the  aggregate 
to  more  than  3000  pounds  a  year  ;  that  is,  to  about  a  ton  and  a  half,  or  to 
more  than  twenty  times  his  weight.  This  enormous  mass  may  well  at- 
tract our  attention  to  the  expenditure  of  material  which  is  required  for 
supporting  life.  It  reveals  to  us  the  fact  that  the  old  physiological  doc- 
trine, that  a  living  being  is  not  influenced  by  external  agents,  is  altogether 
a  fallacy.  A  living  being  is  the  result  and  representative  of  change  on  a 
prodigious  scale. 

The  condition  of  equilibrium  which  has  just  been  set  forth,  moreover, 
Quantity  of  leads  to  the  conclusion  that  the  aggregate  weight  of  urine, 
i^manTifa601  ^eces?  transpired,  and  expired  matter  is  the  same  for  the 
year.  same  period  of  time.  In  round  numbers,  we  may  take  it  at 

a  ton  and  a  half. 

It  can  not  be  questioned  that  the  materials  which  are  rendered  back  to 
the  external  world,  after  having  subserved  the  purpose  of  the  animal  and 
passed  through  its  system,  are  compounds  of  those  which  were  originally 
received  as  food,  drink,  and  air,  though  they  may  have  assumed  in  their 
course  other,  and  perhaps,  in  our  estimation,  viler  forms.  Eecognizing 
as  indisputable  the  physical  fact  that  not  an  atom  can  be  created  any 
more  than  it  can  be  destroyed,  we  should  expect  to  discover  in  the  sub- 
stances thus  dismissed  from  the  system  every  particle  that  had  been 
taken  in. 

What,  then,  is  man  ?  Is  he  not  a  form,  as  is  the  flame  of  a  lamp,  the 
temporary  result  and  representative  of  myriads  of  atoms  that  are  fast 
passing  through  states  of  change — a  mechanism,  the  parts  of  which  are 
unceasingly  taken  asunder  and  as  unceasingly  replaced  ?  The  appear- 
ance of  corporeal  identity  he  presents  year  after  year  is  only  an  illusion. 
He  begins  to  die  the  moment  he  begins  to  breathe.  One  particle  after 
another  is  removed  away,  interstitial  death  occurring  even  in  the  inmost 
recesses  of  the  body. 

From  these  general  considerations  we  infer  that  the  essential  condition 
Great  extent  of  of  life  is  waste  of  the  body ;  and  this  not  only  of  the  body 
the system  of**  in  tne  aggregate,  but  even  of  each  of  its  particular  parts, 
man.  Whatever  part  it  may  be  that  is  exercised  is  wearing  away, 

and  wherever  there  is  activity  there  is  death.  And  since  parts  that  are 
dead  are  useless,  or  even  injurious  to  the  economy,  the  necessities  simul- 
taneously arjse  for  their  removal  and  for  repair.  Much  of  the  compli- 
cated mechanism  of  animal  structures  is  for  the  accomplishment  of  this 
double  duty. 

For  an  organic  being  to  live,  its  parts  must  die.  The  amount  of  activ- 
ity it  displays  is  measured  by  the  amount  of  death,  and  in  this  regard 
every  member  of  the  animal  series  stands  on  the  same  level.  Here,  at 


FIXED  STANDARDS  OF  PHYSIOLOGY.  13 

the  very  outset  of  our  science,  we  must  dismiss  the  vulgar  error  that  the 
physical  conditions  of  existence  vary  in  different  tribes,  and  that  man  is 
not  to  be  compared  with  lower  forms.  We  must  steadily  keep  in  view 
the  interconnection  of  all,  a  doctrine  which  is  the  guiding  light  of  modern 
physiology,  and  which  authorizes  us  to  appeal  to  the  structure  and  func- 
tions of  one  animal  for  an  explanation  of  the  structure  and  functions  of 
another.  The  more  steadily  we  keep  before  us  this  philosophical  con- 
ception of  the  interconnection  of  all  organic  forms,  the  clearer  will  be  our 
physiological  views.  There  has  never  been  created  such  a  thing  as  an 
isolated  living  being. 

From  the  manner  in  which  these  general  considerations  of  the  mechan- 
ical and  chemical  equilibrium  of  the  system  of  man  have  been  Necessity  and 
introduced,  it  will  doubtless  be  seen  that  it  is  the  first  busi-  p^gioiogkfi 
ness  of  the  physiologist  to  disentangle  the  variable  results  standards. 
which  that  system  presents,  as  far  as  may  be  possible,  and  offer  them  un- 
der a  standard  estimate ;  that  at  the  basis  of  this  science  there  should 
be  a  table  setting  forth  with  the  utmost  exactness  all  the  quantities  con- 
cerned in  such  a  standard  type.  Thus,  assuming  the  weight  of  an  adult 
man  at  140  pounds,  as  we  have  done,  it  should  show  the  diurnal  consump- 
tion of  combustible  matter  or  food,  of  water,  of  air — the  diurnal  loss  by 
evaporation,  by  secretion,  by  respiration.  In  contrast  with  this  it  should 
also  give  the  nocturnal.  It  should  also  represent  the  quantity  of  bile, 
of  saliva,  of  pancreatic  juice  ;  the  weight  of  each  one  of  the  various  salts 
and  organic  bodies  they  contain,  the  diurnal  and  nocturnal  production  of 
heat,  &c. 

For  the  purpose  of  the  practice  of  medicine,  a  standard  of  140  pounds 
will  perhaps  be  found  most  convenient,  but  in  a  scientific  point  of  view, 
and  especially  for  comparative  physiology,  a  standard  of  1000  parts  is 
best  assumed.  I  now  present  an  attempt  at  the  construction  of  such  ta- 
bles, it  being  perhaps  scarcely  necessary  to  apologize  for  their  extreme 
imperfection.  Though  offering  the  results  at  present  received  as  most 
trustworthy,  a  very  superficial  examination  will  show  how  full  they  are 
of  errors  and  contradictions.  Perhaps  it  would  not  be  too  much  to  say 
that  it  will  require  the  labor  of  many  physicians,  continued  for  centuries, 
to  bring  such  tables  to  the  truth.  Yet  the  approach  to  precision  in  these 
hypothetical  constants  will  in  all  times  be  a  measure  of  the  exactness  of 
physiology,  and  it  may  be  added,  also,  of  the  practice  of  medicine.  The 
time  is  at  hand  when  such  a  typical  standard  must  be  the  starting-point 
for  pathology,  and  no  rational  practice  can  exist  without  it.  The  passage 
of  physiology,  from  a  speculative  to  a  positive  science,  is  the  signal  for  a 
revolution  in  the  practice  of  medicine. 

Moreover,  physiology  should  furnish  formulas  for  the  computation  of 
variations  in  these  tabular  numbers  under  variable  conditions ;  as,  for  in- 


14  FIXED   STANDAEDS  OF  PHYSIOLOGY. 

stance,  under  low  and  high  aerial  temperatures,  change  of  atmospheric 
pressures,  absolute  quiescence,  or  the  near  approach  thereto,  the  effect  of 
a  determined  amount  of  locomotion,  or  other  muscular  exertion,  &c.  As 
the  science  becomes  more  perfect,  it  should  likewise  attempt  to  embrace 
pathological  states ;  as,  for  instance,  the  diurnal  or  periodic  production  of 
heat  in  fevers,  the  effect  of  the  hygienic  system  of  the  bedroom. 

Physiology  having  attained  to  this  high  condition,  the  practice  of  med- 
icine in  its  great  department  of  diagnosis  will  consist,  in  reality,  in  the 
solution  of  inverse  problems.  Given  the  variations  from  the  standard  ex- 
isting in  any  case,  to  determine  the  cause  of  those  variations.  At  this 
point  diagnosis  becomes  a  science,  and  ceases  to  be  an  art. 

As  in  painting  and  statuary,  the  artist  has  an  ideal  model  in  his  mind, 
Illustration  of  a  ^7P^ca^  standard  which  no  living  being  has  perfectly  reach- 
the  following  ed,  though  some  of  the  most  beautiful  may  have  approached 
thereto,  so  in  physiology  the  standard  or  typical  man  pre- 
sents the  combined  and  mean  values  of  all  the  human  race. 

A  less  comprehensive  view  presents  us  with  distinct  national  standards, 
instead  of  this  universal  one,  for  every  country  has  its  own  peculiarities. 
Eesults  of  the  highest  interest  are  to  be  perceived  when  these  national 
standards  are  compared  with  one  another.  Even  the  same  nation  must 
offer,  from  age  to  age,  modifications  in  its  type  expressive  of  the  secular 
perturbations  it  is  undergoing,  as  it  advances  or  descends  in  a  knowledge 
of  the  arts  of  life  and  civilization. 

Moreover,  there  are  typical  standards  of  a  still  lower  order,  having  ref- 
erence to  the  conditions  of  sex  and  the  period  of  life.  Of  these  six  may 
be  designated — the  infant,  the  adult,  the  aged,  of  the  male  and  female  sex 
respectively. 

As  illustrations  of  these  remarks,  and  examples  of  the  determination  of 
the  fundamental  element  of  such  a  general  physiological  table,  the  stand- 
ard weight  of  the  body,  we  may  take  the  following  estimates.  An  ex- 
amination of  20,000  infants,  at  the  Maternite  in  Paris,  gives  for  the  weight 
of  the  new-born  6  Jibs. ;  the  same  mean  value  obtains  for  the  city  of  Brus- 
sels. For  about  a  week  after  birth  this  weight  undergoes  an  actual  dim- 
inution, owing  to  the  tissue  destruction  which  ensues  through  the  estab- 
lishment of  aerial  respiration,  and  which  for  the  time  exceeds  the  gain 
from  nutrition.  For  the  same  age  the  male  infant  is  heavier  than  the  fe- 
male, but  this  difference  gradually  diminishes,  and  at  twelve  years  their 
weight  is  sensibly  the  same.  Three  years  later,  at  the  period  of  puberty, 
the  weight  is  one  half  of  what  it  is  finally  to  be,  when  full  development 
is  reached.  The  maximum  weight  eventually  attained  is  a  little  more 
than  twenty  times  that  at  birth,  this  holding  good  for  both  sexes ;  but 
since  the  new-born  female  weighs  less  than  the  standard,  and  the  new- 
born male  more,  the  weight  of  the  adult  male  is  136^^-  Ibs.,  and  of  the 


PHYSIOLOGICAL  TABLES. 


15 


adult  female  121^^^  Ibs.  The  mean  weight  of  a  man,  irrespective  of  his 
period  of  life,  is  103^^  Ibs.,  and  of  a  woman  93^^^-  Ibs.  The  mean 
weight  of  a  human  being,  without  reference  either  to  age  or  sex,  is 


For  the  preceding  numbers  we  are  indebted  to  the  researches  of  M. 
Quetelet,  who  likewise  has  in  an  interesting  manner  extended  the  meth- 
ods of  statistics  to  the  illustration  of  the  physical  and  moral  career  of 
man,  and  impressed  us  with  the  facts  that  in  the  discussion  of  the  phe- 
nomena which  masses  present,  individual  peculiarity  disappears  and  gen- 
eral laws  emerge.  The  actions  which  seem  to  be  the  result  of  free  will 
in  the  individual,  assume  the  guise  of  necessity  in  the  community.  Just 
as  we  are  sure  that  man  is  born,  develops,  and  dies  under  the  operation 
of  laws  that  are  absolutely  invariable,  so  communities  seem  to  be  under 
the  influence  of  unchangeable  laws.  "  In  communities  man  commits  the 
same  number  of  murders  each  year,  and  does  it  with  the  same  weapons. 
We  might  enumerate  beforehand  how  many  individuals  will  imbrue  their 
hands  in  the  blood  of  their  kind,  how  many  will  forge,  how  many  poison, 
very  nearly  as  we  enumerate  beforehand  how  many  births  and  deaths  will 
take  place." 

PHYSIOLOGICAL  STANDAKD  TABLES. 


Diurnal  Ingesta,  Secretions,  and  Excretions  of  a  Man  whose 
•eight  is  140  Ibs.  avoirdupois. 


Diurnal  Ingesta,  Secretions,  and  Excretions  of  a  Man  whosa 
•weight  is  1000  parts. 


Weight  of  body 140.000 

fWater 4.109 

I  Oxygen 2.192 

]  Dry  vegetable  food. . .      1.687 

S  I  Dry  animal  food 563 

Saliva 3.300 

Gastric  j  uice 14. 080 

Pancreatic  juice 440 

Bile 3.500 

5     Carbon  from  lungs  . . .        .500 

•j3     Intestinal  juice 440 

£     Loss  of  water  by  lungs     1.440 
"          skin.      2.234 

Fseces OT8 

Urine 2.180,  consisting  of 


Water 2.034 

Urea 065 

Uric  acid 002 

Lactic  acid 037 

Sulphuric  acid 007 

Phosphoric  acid 008 

Chloride  of  sodium  .  .009 
Alkalies  and  earths .  .  016 

Other  bodies 002 

TBlcod  . . .  •„ 17.000,  consisting  of 

Water 13.328 

Albumen 1.190 

Fibrin i...      .037 

Discs 2.227 

Fats 022 

Chloride  of  sodium  .061 
Chloride  of  potass  .  .  006 
Phosphate  of  soda  .  .003 
Carbonate  of  soda  .  .012 
Sulphate  of  soda. . .  .004 
Phos.  lime  and  mag  .004 
Oxide  and  phos.  iron  .008 
Other  bodies 098 


In  this  table  the  estimate  is  in  the 
pound  and  decimals  thereof. 


ivoirdupois 


Weight  of  body 1000.000 

tfWater 29.350 
J  Oxygen  .' 15.057 
_  |  Dry  vegetable  food  . .      12.050 

w  I  Dry  animal  food 4. 021 

Saliva 23.576 

Gastric  j  uice 100.571 

Pancreatic  j  uice 3. 143 

Bile 25.000 

Carbon  from  lungs. . .        3.571 

:E     Intestinal  juice 3.143 

2     Loss  of  water  by  lungs     10. 286 
8         "  "          skin.      15.957 

a     Faeces 557 

Urine 15.571,  consisting  of 

Water 14.529 

Urea 464 

Uric  acid 014 

Lactic  acid 264 

Sulphuric  acid 050 

Phosphoric  acid  ...  .057 
Chloride  of  sodium  .  064 
Alkalies  and  earths  .114 

Other  bodies 014 

121.429,  consisting  of 

Water 95.200 

Albumen 8.500 

Fibrin 264 

Discs 15.907 

Fats 157 

Chloride  of  sodium .  .  436 
Chloride  of  potass  . .  .043 
Phosphate  of  soda  . .  .021 
Carbonate  of  soda  . .  .OSM» 

Sulphate  of  soda 029 

Phos.  lime  and  mag.  .029 
Oxide  and  phos.  iron  .057 

Other  bodies 700 

In  this  table  the  estimate  is  upon  one  thousand 
parts. 


It  is  to  be  received  as  a  doctrine  admitting  no  controversy,  that  or- 


16  NATURE   OF  MATTERS  RECEIVED. 

ganic  systems,  whether  vegetable  or  animal,  whether  humble  or  elaborate- 
An  animal  ere-  \y  developed,  possess  no  power  of  creating  material.  Their 
buToSy  trfns-  function  is  of  necessity  limited  to  the  mere  transformation  of 


forms  the  sub-  substances  furnished  to  them.  From  this  it  follows,  even  in 
ceives.  the  case  of  man,  that  the  substances  dismissed  from  the  sys- 

tem are  metamorphosed  forms  of  those  which  have  been  received,  and 
that,  whatever  their  appearance  may  be,  they  must  have  arisen  from  the 
reaction  of  the  food,  water,  and  air  upon  one  another. 

This  reaction  we  may  proceed  to  view  as  a  purely  chemical  result  ; 
for,  casting  aside  all  the  vain  hypotheses  of  the  older  physiology,  and  per- 
mitting ourselves  to  be  guided  by  the  harmonies  of  nature,  we  should  ex- 
pect to  recognize  in  the  changes  taking  place  in  organic  systems,  and  in 
the  phenomena  which  attend  those  changes,  the  same  results  which  arise 
in  the  artificial  or  experimental  reaction  of  food,  water,  and  air  on  each 
other.  A  very  superficial  examination  of  the  facts  shows  at  once  the 
The  chemical  correctness  of  this  expectation.  On  such  an  examination  we 
mauersre-^  now  enter>  premising  it  with  some  general  remarks  needful  for 
ceived.  our  purpose  on  the  nature  and  properties  of  food,  water,  and  air. 

1st.  OF  FOOD.  —  No  article  is  suitable  for  food  except  it  be  of  a  com- 
bustible nature.  Its  chemical  constitution  must  be  such  that  if  its  tem- 
perature be  raised  to  a  proper  degree  with  a  due  access  of  atmospheric  air 
it  will  take  fire  and  burn,  and  the  products  of  its  combustion  must  be  car- 
bonic acid  gas  and  water,  or  those  substances  with  nitrogen  or  its  com- 
pounds. 

2d.  OF  WATER.  —  This  may  be  taken  as  the  type  and  representative 
of  all  the  various  liquids  used  as  drinks.  It  evaporates  at  any  tempera- 
ture, even  at  those  which  are  lower  than  its  freezing  point,  and  in  this 
evaporation  produces  cold.  Water  vaporizing  from  the  skin  absorbs  1114 
degrees  of  heat,  and  hence  exerts  a  most  powerful  refrigerating  action. 
Over  saline  substances  there  are  few  bodies  which  exercise  so  general  a 
solvent  effect.  In  virtue  of  this  property,  it  is  enabled  to  introduce  in 
the  dissolved  state  such  compounds  as  are  wanted  for  the  nutrition  of  the 
system,  and  in  the  same  manner  to  carry  away  the  wasted  products  of 
decay. 

3d.  OF  ATMOSPHERIC  AIR.  —  The  active  principle  of  the  air  is  oxygen 
gas,  the  effects  of  which  are  moderated  by  the  presence  of  a  large  quanti- 
ty of  nitrogen-  —  four  fifths  of  the  air  consisting  of  this  latter  substance. 
Physiologically,  we  often  use  the  terms  atmospheric  air  and  oxygen  syn- 
oifymously. 

The  chief  materials  which  a  living  being  receives  from  the  external 
world  are,  therefore,  COMBUSTIBLE  MATTER,  WATER,  OXYGEN  GAS  ;  and  out 
of  the  action  of  these  upon  one  another  all  the  physical  phenomena  of  its 
life  arise. 


NATUEE  OF  MATTEES  EESTOEED.  17 

Such  being  the  nature  and  properties  of  the  things  received,  we  may 
now  examine  in  the  same  general  manner  those  which  are  Properties  of 
dismissed  from  the  system.  Here,  at  the  very  outset,  we  en-  substances 

.  -,.  -,•  dismissed  bv 

counter  the  important  fact  that  they  are  oxidized  or  burned  the  system." 
bodies. 

1st.  As  respects  the  urine  and  its  constituents.  Its  liquid  part,  wa- 
ter, is  an  oxide  of  hydrogen,  of  which,  though  the  greater  portion  may 
not  have  been  produced  in  the  economy,  yet  a  certain  quantity  unques- 
tionably has.  In  it,  too,  are  to  be  found  sulphuric  acid,  which  is  an  ox- 
ide of  sulphur ;  phosphoric  acid,  which  is  an  oxide  of  phosphorus  ;  and  its 
leading  solid  constituent,  urea,  is  the  representative  of  bodies  which  arise 
when  processes  of  oxidation  have  been  going  on. 

2d.  The  expired  and  transpired  matters  present  similar  burned  com- 
pounds. At  the  head  of  these  products  stand  carbonic  acid  gas,  which  is 
an  oxide  of  carbon,  and  water,  which,  as  we  have  already  said,  is  an  ox- 
ide of  hydrogen.  We  here  omit  any  consideration  of  the  nature  or  con- 
stitution of  the  fecal  matter,  because  much  of  it  has  never  been  properly 
in  the  interior  of  the  system,  though  it  has  passed  through  the  intestine. 

The  general  result  at  which  we  arrive  is,  then,  that  the  food  consists  of 
combustible  matter,  and  that  the  substances  dismissed  from  the  economy 
are  oxidized  bodies.  A  burning  must,  therefore,  have  been  go-  comkustjon 
ing  on,  and  this  could  only  have  been  accomplished  by  the  air  occurs  in  the 
introduced  by  breathing  acting  upon  the  substance  of  the  body  oc  y' 
itself  and  its  contents,  and,*  to  repair  the  waste  which  must  have  ensued, 
a  due  weight  of  food  has  been  required.  Since  this,  in  its  turn,  as  a 
part  of  the  living  mechanism,  is  destined  to  undergo  the  like  destructive 
action,  we  may  present  the  entire  series  of  facts  under  consideration  cor- 
rectly by  regarding  them  as  arising  remotely  from  the  action  of  the  air 
upon  the  food. 

With  this  statement  before  us,  we  next  inquire  what  ensues  when  sub- 
stances appropriate  for  food  are  exposed  in  artificial  experiments  at  a  cer- 
tain temperature  to  the  action  of  atmospheric  air. 

A  piece  of  flesh,  or  even  of  any  vegetable  body,  consisting  of  carbon, 
hydrogen,  oxygen,  and  nitrogen,  submitted  to  those  condi-  Results  of  arti- 
tions,  undergoes  combustion.  Its  carbon,  by  uniting  with  ox-  fi.cial  combus- 

\     J  &  tion  the  same 

ygen,  produces  carbonic  acid,  its  hydrogen  for  the  most  part  as  that  in  the 
water,  but  a  residue  thereof,  combining  with  the  nitrogen,  may  bodjr- 
give  rise  to  the  production  of  ammonia.     If  there  be  any  sulphur  and 
phosphorus  present,  they  also  burn,  and  salts  of  sulphuric  and  phosphoric 
acids  are  the  result. 

Such  is  what  occurs  outside  of  the  body  in  a  common  case  of  artificial 
combustion  where  atmospheric  air  has  access.  The  constituents  of  which 
the  food  is  composed  thus  satisfy  their  chemical  affinities,  and  the  com- 

B 


18  PEODUCTION   OF   HEAT. 

pounds  we  have  mentioned  arise.  Now  it  is  a  fact  of  the  utmost  signifi- 
cance that  the  compounds  thus  originating  from  the  direct  artificial  "burn- 
ing of  matters  proper  for  food  are  the  very  same  that  are  dismissed  from 
the  animal  system  in  which  food  has  been  submitted  to  the  air  introduced 
by  respiration.  They  are  such  substances  as  carbonic  acid,  water,  am- 
monia, sulphates  and  phosphates. 

It  may  impress  these  truths  more  deeply  upon  us  to  learn  that  the 
facts  at  which  we  have  thus  arrived  may  also  be  recognized  m  the 
changes  of  destruction  presented  by  the  vegetable  kingdom.  The  leaves 
of  trees,  after  they  have  fallen  in  autumn,  quickly  decay,  and  even  the 
heart- wood  itself  has  a  limit  beyond  which  it  does  not  last.  Sooner  or 
later  every  part  of  a  plant  is  destroyed  by  the  atmospheric  air.  Such 
limits  of  duration  in  animal  structures  are  short.  A  very  brief  time,  per- 
haps only  a  few  hours,  is  all  that  is  wanted  for  putrefaction  to  set  in,  and 
the  entire  mass,  undergoing  dissolution,  is  lost  in  the  surrounding  air. 

This  final  disappearance  of  all  organized  structures  is  brought  about 
by  the  action  of  that  energetic  element,  oxygen.  If  by  any  contrivance 
its  influence  is  prevented  and  its  presence  avoided,  these  changes  do  not 
take  place.  Putrefaction  and  decay  are  slow  combustions,  true  burnings 
taking  time.  There  equally  arise  from  the  fallen  leaf  and  from  the  de- 
caying body  carbonic  acid,  water,  and  ammonia,  the  self-same  substances 
dismissed  from  the  economy  during  the  continuance  of  life. 

Processes  of  combustion  and  processes  of  decay  are  therefore  both  due 
to  the  action  of  atmospheric  oxygen  on  the  changing  substance.  They 
differ  chiefly  from  one  another  in  the  relative  rapidity  with  which  they 
are  accomplished. 

The  facts  thus  set  forth  wan-ant  the  following  statements.  The  mat- 
ters which  a  man  receives  as  food  are  combustible  bodies ;  those  dismissed 
Production  of  from  his  system  have  been  burned.  To  that,  as  to  any  other 
animal  heat.  g^^  burning,  oxygen  gas  is  absolutely  requisite.  There  is, 
therefore,  a  plain  conclusion  before  us,  which,  in  its  far-reaching  conse- 
quences, covers  the  whole  science  of  physiology,  and  betrays  to  us  the 
function  which  every  animal  discharges,  viz.,  that  oxidation  is  incessant- 
ly going  on  in  the  interior  of  the  system  through  the  agency  of  atmos- 
pheric air  introduced  by  the  process  of  breathing. 

An  animal,  in  this  point  of  view,  is  an  oxidizing  machine,  into  the  in- 
terior of  which  atmospheric  air  is  constantly  introduced.  The  active  con- 
stituent, oxygen,  satisfies  its  chemical  affinities  at  the  expense  of  those 
parts  of  the  system  which  are  wasting  away.  And  as  the  act  of  breath- 
ing, that  is,  the  introduction  of  this  gas,  takes  place  day  and  night,  wak- 
ing and  sleeping,  so  too  must  the  production  of  burned  bodies ;  a  part 
escaping  by  the  lungs,  a  part  by  the  skin,  a  part  in  the  urine.  To  com- 
pensate the  loss  which  ensuess  nearly  1000  pounds  weight  of  combustible 


PRODUCTION   OF  HEAT.  19 

matter  must  be  used  in  the  course  of  a  year,  and,  for  reasons  to  be  exam- 
ined in  detail  presently,  three  quarters  of  a  ton  of  water.  But  this  is  a 
very  different  conclusion  to  the  notion  of  the  ancient  physicians,  that  an 
animal  during  its  life  is  exempt  from  participating  in  external  changes, 
and  is  an  enduring  monument  of  the  power  possessed  by  the  VITAL  FORCE 
of  resisting  all  physical  influences. 

But  carbon  by  uniting  with  oxygen  can  not  turn  into  carbonic  acid, 
nor  can  hydrogen  turn  into  water,  nor  nitrogen  into  ammonia,  without 
heat  being  produced.  The  very  meaning  we  attach  to  the  term  indicates 
that  every  process  of  burning  is  attended  with  the  liberation  of  heat. 

In  domestic  economy,  we  protect  ourselves  from  the  cold  weather  of 
winter,  or  attain  any  high  temperature  we  want  by  the  oxidation  of  some 
of  the  forms  of  carbon,  such  as  wood  or  coal,  in  fire-places  or  stoves. 
"We  know  that  for  the  production  of  a  given  quantity  of  heat  a  given 
weight  of  combustible  matter  and  of  air  is  required,  and  that  by  employ- 
ing various  mechanical  contrivances  for  increasing  the  draught  we  can  ac- 
celerate* the  burning. 

Moreover,  if  in  our  laboratories  we  require  the  very  highest  tempera- 
ture that  can  be  artificially  obtained,  we  resort  to  the  burning  of  hydro- 
gen. There  are  instruments,  such  as  the  compound  blow-pipe,  construct- 
ed on  this  principle.  In  the  flame  which  arises  in  this  combustion  the 
most  refractory  substances  melt  or  are  deflagrated. 

But  it  may  be  said  that  though  when  a  substance  is  rapidly  oxid- 
izing it  must  be  evolving  heat,  there  is  perhaps   a  slower  Production  of 
kind  of  combination,  in  which  the  particles  unite  without  any  ^^™  J^re" 
disturbance  of  temperature.     What  proof  could  be  offered,  for  decay, 
example,  that  a  mouldering  leaf  is  disengaging  heat  ? 

In  answer  to  this  it  is  not  necessary  to  bring  forward  refined  or  direct 
experiments.  Every  leaf  when  it  moulders  is  literally  burning  away. 
The  extrication  of  warmth  begins  even  when  it  is  ready  to  fall.  What 
does  the  farmer  expect  in  making  his  hay,  if  he  puts  the  grass  up  in  too 
moist  a  state,  or  in  too  large  a  mass  ?  The  temperature  does  not  stop  at 
the  stage  of  bituminous  fermentation,  but  the  stack  most  probably  takes 
fire.  Of  course  what  is  going  on  in  the  whole  mass  is  going  on  in  each 
separate  leaf,  undistinguishable,  it  is  true,  in  the  latter  case,  because  the 
heat  of  a  single  decaying  leaf,  taken  alone,  may  be  carried  off  by  the  cold 
surrounding  air,  or  by  the  contact  of  good  conducting  bodies,  and  so  be 
lost  to  examination. 

From  agricultural  operations  we  may  also  learn  that  what  holds  good 
for  vegetable  bodies  is  true  for  animal  substances.  Heaps  of  manure  or 
of  offal  of  any  kind,  if  due  access  of  air  be  given,  exhibit  the  extrication 
of  carbonic  acid,  steam,  and  ammonia,  and  the  temperature  promptly  rises. 
The  gardener  avails  himself  of  this  fact.  He  uses  the  heat,  as  it  is  slowly 


20,  REGULATION   OF  HEAT. 

set  free  by  the  putrefaction  of  manure  in  his  forcing  frames,  to  bring  forth 
plants  in  the  early  spring.  There  is  no  kind  of  decay,  or  putrefaction,  or 
oxidation  of  organic  matters,  however  slow  it  may  be,  that  is  not  marked 
by  the  production  of  warmth. 

Man,  in  a  state  of  health,  maintains  a  nearly  uniform  temperature. 
Heat  of  man:  Neglecting  slight  variations,  to  be  hereafter  critically  exam- 
its  cause.  wed,  it  is  98  degrees.  For  the  most  part,  it  is  immaterial 
in  what  climate  of  the  earth  he  may  reside,  whether  in  the  cold  polar  re- 
gions or  the  hot  tropic ;  he  is  so  constituted  that,  either  through  the  pro- 
visions of  his  own  organization,  or  by  resorting  to  the  adventitious  aid  of 
clothing,  or  to  special  articles  of  food,  he  can  maintain  himself  at  about 
the  same  degree ;  and  as  all  this  heat  arises  from  interstitial  oxidation 
continually  taking  place,  it  is  obvious  that  within  certain  limits  he  has 
control  over  it.  Thus,  in  the  winter  he  sometimes  resorts  to  violent  mus- 
cular action  in  order  to  increase  the  rapidity  of  respiration  and  the  de- 
struction of  muscular  tissue ;  for  the  greater  the  quantity  of  air  intro- 
duced in  a  given  period  of  time,  the  higher  the  temperature  rises,  just 
as  when  we  close  the  door  of  a  stove,  or  place  a  blower  on  an  anthracite 
fire,  an  increased  draught  is  occasioned  and  the  quantity  of  heat  is  in- 
creased. To  breathe  with  rapidity  and  depth  is  certain  to  raise  the  tem- 
perature. 

On  the  contrary,  in  summer,  when  the  heat  is  oppressive,  we  instinct- 
ively abstain  from  muscular  exertion,  tranquil  and  slow  respiration  goes 
on,  and  the  temperature  is  kept  down.  Again,  there  are  means  of  occa- 
sioning an  increased  liberation  of  heat  by  changing  the  nature  of  the  food 
and  using  highly  combustible  material,  such  as  the  various  kinds  of  alco- 
holic preparations.  The  chemical  constitution  of  alcohol  is  such  that  in 
the  act  of  burning  carbonic  acid  and  water  are  produced  with  the  libera- 
tion of  so  much  heat  that  chemists  find  it  one  of  the  most  suitable  means 
of  attaining  a  high  temperature.  On  taking  preparations  of  this  substance, 
such  as  distilled  liquors  or  wines,  the  first  effect  is  the  production  of  a 
genial  warmth  all  over  the  body,  intoxication  eventually  coming  on  as  a 
secondary  result. 

These  remarks  are  not  limited  in  their  application  to  our  own  species, 
the  whole  animal  world  furnishes  us  with  commentaries  on  their  truth. 
Man  maintaining  a  temperature,  as  has  been  said,  of  about  98  degrees, 
other  animals  are  at  other  degrees,  some  being  cold-blooded  and  some  hot. 
The  particular  point  they  reach  depends,  as  direct  observation  shows,  on 
the  quantity  of  oxygen  they  consume,  or,  in  other  words,  on  their  respira- 
tion. Birds,  whose  breathing  mechanism  is  by  far  the  most  elaborate 
and  extensively  developed,  have  by  far  the  highest  temperature.  The 
snake  or  the  tortoise,  whose  rate  of  respiration  is  very  slow,  and  which 
consume  but  little  oxygen,  have  a  correspondingly  low  degree  of  heat. 


USES  OF  WATER.  21 

And  in  those  creatures  which  at  one  period  of  the  year  are  in  full  activity, 
but  at  another  lie  dormant  or  hibernate,  as  they  begin  to  respire  more 
slowly  their  temperature  begins  to  decline,  and  when  they  have  sunk  into 
their  winter's  sleep  their  breathing  is  scarcely  perceptible,  and  their 
warmth  scarcely  above  that  of  the  surrounding  air. 

In  what  has  been  thus  far  said  we  have  been  considering  those  oper- 
ations of  the  system  which  tend  to  the  production  of  heat,  causes  of  cooi- 
and  the  maintenance  of  the  whole  mass  of  the  body  at  a  tern-  ing  of  the  body. 
perature  above  that  of  the  surrounding  air.  But  it  is  obvious  that  pro- 
vision must  be  made  to  prevent  any  undue  rise,  so  that  between  those 
causes  of  elevation  and  these  of  depression  a  due  equilibrium  may  be  main- 
tained. If  a  very  large  quantity  of  combustible  matter,  under  the  form  of 
food,  and  about  an  equal  weight  of  oxygen,  are  necessary  for  obtaining  a 
proper  heat,  we  should  also  recollect  that  nearly  three  quarters  of  a  ton  of 
water  are  consumed  each  year.  The  duty  which  this  water 

J  J  Uses  of  water. 

discharges  we  may  next  consider. 

That  duty  is  twofold.  1st.  The  removal  of  solid  material  in  a  state 
of  solution ;  and,  2d.  The  production  of  cold  by  evaporation.  It  is  the 
cooling  agency  which  is  of  most  interest  to  us  in  our  present  inquiry,  but 
a  few  remarks  as  regards  the  removal  of  solid  matter  may  not  here  be 
misplaced. 

1st.  Water,  then,  exerts  its  solvent  power  for  the  removal  of  all  those 
substances  which,  arising  incessantly  in  the  animal  system,  can  its  solvent 
not  assume  either  the  vaporous  or  gaseous  state.  In  this  con-  P°wer- 
dition  are  the  different  saline  bodies,  such  as  the  sulphates  which  are  com- 
ing from  the  destruction  of  the  muscular  tissues,  as  voluntary  and  invol- 
untary motions  are  performed ;  or  the  phosphates  which  are  produced  by 
the  destruction  of  cerebral  and  nervous  'matter.  In  the  same  condition 
starid  nearly  all  the  nitrogenized  results  of  the  destruction  of  the  soft 
parts,  and  which  are  to  a  great  extent  to  be  removed  as  urea.  Water  dis- 
solving with  more  or  less  facility  these  various  bodies  permits  their  escape 
from  the  system  by  the  secreting  action  of  the  kidneys,  which,  strain- 
ing or  filtering  them  from  the  blood,  dismiss  them  to  the  bladder,  from 
which  they  are  periodically  removed. 

The  skin  is  no  inefficient  auxiliary  to  the  kidneys  in  effecting  this  re- 
moval of  water  charged  with  soluble  matters.  All  over  its  surface  are 
scattered  in  profusion  the  ducts  of  the  perspiratory  glands,  which  consist 
of  a  convoluted  tubing  abundantly  supplied  with  blood-vessels.  The  final 
mode  of  action  of  these  glands  depends  on  extraneous  circumstances. 
Most  commonly  the  fluid  is  carried  away  under  the  form  of  a  vapor  or  in- 
sensible perspiration,  but  when  the  secretion  goes  on  more  rapidly,  or  the 
dew-point  of  the  surrounding  air  is  high,  it  then  accumulates  as  drops  of 
sweat.  The  amount  of  water  thus  removed,  even  by  insensible  perspira- 


?2  COOLING  BY  EVAPORATION. 

tion,  is  greater  than  might  be  supposed,  yet  it  corresponds  with  the  ex- 
tent of  the  provision.  The  length  of  the  water-secreting  tubing  in  the 
skin  of  a  man  is  about  twenty-eight  miles. 

Thus  by  the  action  of  the  kidneys  and  the  skin  large  quantities  of  wa- 
ter are  dismissed,  either  under  the  liquid  or  vaporous  form.  A  third  or- 
gan is  concerned  in  this  important  duty.  It  is  the  lungs.  These,  how- 
ever, are  limited  in  their  operation  to  its  exhalation  as  vapor  or  steam. 
That  water  abundantly  escapes  from  them  is  plainly  shown  when  the  days 
are  cold,  the  moisture  as  it  comes  from  the  respiratory  passages  condens- 
ing into  a  visible  cloud  when  it  encounters  the  air.  It  is  estimated  that 
the  loss  of  water  by  the  skin  and  lungs  conjointly  is  about  18  grains  in 
a  minute,  of  which  11  pass  off  from  the  skin  and  7  from  the  lungs.  Mak- 
ing due  allowance  for  the  variable  action  of  the  skin  as  dependent  on  the 
dew-point  and  other  such  causes,  we  can  scarcely  set  down  the  entire 
quantity  at  less  than  1000  pounds  a  year.  In  the  same  period  the  quan- 
tity of  water  lost  as  urine  may  be  taken  at  900  pounds.  It  may  perhaps 
be  remarked,  that  here  we  are  assuming  a  loss  of  1900  pounds,  when  the 
quantity  of  water  annually  taken  is  only  1500  pounds.  But  it  is  to  be 
recollected  that  not  only  does  water  form  a  very  prominent  constituent  of 
the  solid  food,  whether  vegetable  or  animal,  but  also  that  much  arises 
from  the  oxidation  of  hydrogen  in  the  interior  of  the  system. 

2d.  Water  also  exerts  a  cooling  influence,  arising  from  its  evapora- 
Cooling  influ-  tion  from  the  surface  of  the  skin  and  the  cells  of  the  lungs, 
ence  of  water,  rpj^  difference  between  water  in  the  state  of  an  invisible  va- 
por and  in  the  liquid  condition  consists  in  this,  that  the  vapor  contains 
1114  degrees  of  heat  which  the  liquid  does  not.  When,  therefore,  it 
evaporates  from  a  surface  of  any  kind,  as  from  the  skin,  it  obtains  there- 
from that  large  amount  of  latent  heat,  and  so  tends  to  cause  the  tempera- 
ture to  decline.  Not  that  this  is  the  only  cooling  agency  at  work.  *  Ka- 
diation  might  also  be  mentioned ;  for,  just  as  a  warm  inorganic  body  cools 
by  the  escape  of  radiant  heat  from  it,  so  too  does  a  living  being. 

These  considerations  explain  how  an  equilibrium  of  temperature  is  es- 
Equiiibrium  of  tablished.  By  the  process  of  respiration  there  is  a  constant 
heat  in  man.  tendency  to  increase  the  heat ;  but  by  evaporation  of  water, 
radiation,  and  other  cooling  causes,  tllere  is  a  constant-tendency  to  dimin- 
ish it.  A  balance  is  struck  between  the  two  processes,  and  in  man  a 
temperature  of  98  degrees  is  kept  up. 

This  average  temperature  is,  however,  easily  departed  from.  Through 
some  trivial  cause  the  cooling  agencies  may  be  interfered  with,  and  then, 
the  heating  processes  getting  the  superiority,  a  high  temperature  or  fe- 
ver comes  on.  Or  the  reverse  may  ensue.  In  Asiatic  cholera,  the  con- 
stitution of  the  blood  is  so  changed  that  its  cells  can  no  longer  carry  ox- 
ygen into  the  system,  the  heat-making  processes  are  put  a  stop  to,  and> 


PHYSICAL  MECHANISM   OF  MAN.  23 

the  temperature  declining,  the  body  becomes  of  a  marble  coldness  charac- 
teristic of  that  terrible  disease. 

The  animal  mechanism  is  thus  the  focus  of  intense  chemical  changes, 
and  great  quantities  of  material  are  required  in- very  brief  Necessity  of  re- 
spaces  of  time  for  its  support.  We  have  seen  what  is  the  {^^ft*1**" 
use  of  the  combustible  matter  employed  as  food,  what  of  the  wastes. 
water,  what  of  the  air,  how,  these  reacting  on  one  another,  a  high  but  reg- 
ulated temperature  is  kept  up. 

Much  of  what  has  been  thus  far  said  has  had  reference  only  to  the  de- 
struction of  tissues.  This  waste  of  matter  arises  for  a  double  reason, 
partly  to  give  origin  to  the  heat  which  animals  require,  and  partly  as  a 
consequence  of  intellectual  activity  and  muscular  motion ;  for  no  move- 
ment can  be  made  without  a  destruction  of  muscular  fibre,  and  all  mental 
and  nervous  actions  imply  the  waste  of  a  certain  quantity  of  vesicular 
substance.  For  this  reason,  after  an  animal  has  undergone  violent  mus- 
cular exercise,  the  quantity  of  urea  and  sulphuric  acid  in  the  urine  is  in- 
creased, this  being  the  channel  through  which  those  results  of  the  de- 
struction of  muscular,  fibre  are  removed ;  or,  after  severe  mental  or  intel- 
lectual duty,  there  is  more  phosphoric  acid  than  usual  in  the  urine,  be- 
cause of  the  greater  oxidation  of  phosphorus  which  has  taken  place  in 
the  brain. 

But  of  course  this  destruction  of  tissue  must  be  compensated  by  a  re- 
pair if  a  normal  condition  and  health  are  preserved.  The  action  of  the  air 
is  not  directly  upon  the  food,  for  intermediately  and  temporarily  the  food 
is  converted  into  the  living  mechanism.  The  dead  material  is  awakened 
into  life,  and  for  a  time,  though  only  for  a  time,  becomes  a  portion  of  the 
living  and  feeling  mass. 

The  functions  and  actions  we  have  been  considering  imply  the  provi- 
sion of  many  complicated  mechanisms.  There  must  be  means  various  mech- 
for  effecting  the  introduction  of  the  air ;  these,  in  man,  depend  anisms  wanted 

iv        -    ,  ,.        ..  A  {•  A    i        •      f°r  removal  of 

on  calling  into  operation  its  pressure.  A  system  of  tubes  is  waste  and  for 
necessary  for  its  distribution  to  the  points  at  which  it  is  re-  repair, 
quired,  and  in  like  manner  a  system  is  required  for  carrying  away  the 
wasted  products  of  decay.  The  new  material  which  is  destined  to  re- 
place the  parts  which  are  thus  disappearing,  and  to  keep  the  economy  in 
repair,  must  be  submitted  to  such  processes  of  mechanical  and  chemical 
preparation  that  it  may  be  dissolved  in  the  blood,  and  carried  wherever  it 
is  wanted.  It  must  therefore  be  cut  and  crushed  by  teeth  driven  by  pow- 
erful muscles,  dissolved  by  acid  and  alkaline  juices  in  digestive  cavities 
set  apart  for  that  purpose.  From  these  it  must  be  taken  by  arrange- 
ments which  can  absorb  it  and  carry  it  into  the  torrent  of  the  circulation. 
Physical  means  must  be  resorted  to,  not  only  for  the  impulsion  of  these 
newly-absorbed  nutritive  juices,  but  likewise  to  drive  the  blood  in  its 


24  THE   SOUL. 

proper  career  of  circulation.  It  is  needless  here  to  dwell  on  the  manner 
in  which  the  most  refined  principles  of  hydraulics  are  brought  into  play, 
or  to  speak  of  the  manner  in  which  forces  of  compression  and  elasticity 
are  introduced ;  how  that  there  are  valves  which  open  only  in  one  way 
to  let  the  current  pass,  or  how  some  of  these,  as  in  the  like  human  con- 
trivances, are  tied  down  in  their  action  by  cords.  Moreover,  since  it  is 
required  that  the  animal  shall  go  in  search  of  its  food,  muscles  of  loco- 
motion, which  act  upon  purely  mechanical  principles  on  the  bony  skele- 
ton, must  be  resorted  to,  and  so  the  animal  structure  becomes  a  most 
elaborate  and  complicated  machine.  • 

In  this  regard  the  human  body  may  be  spoken  of  as  a  mere  instrument 
Physical  as-  or  engine,  which  acts  in  accordance  with  the  principles  of  me- 
pectofman.  chanical  and  chemical  philosophy,  the  bones  being  levers,  the 
blood-vessels  hydraulic  tubes,  the  soft  parts  generally  the  seats  of  oxida- 
tion. But  if  we  limit  our  view  to  such  a  description,  it  presents  to  us 
man  in  a  most  incomplete  and  unworthy  aspect.  There  animates  this 
machine  a  self-conscious  and  immortal  principle — the  soul. 

Though  in  the  most  enlarged  acceptation  it  would  fall  under  the  prov- 
Thesoui-  its  *nce  °^  P^7s^°g7  to  *reat  of  this  immortal  principle,  and  to 
nature  and  re-  consider  its  powers  and  responsibilities,  these  constitute  a 
ies'  subject  at  once  so  boundless  and  so  important,  that  the  phys- 
iologist is  constrained  to  surrender  it  to  the  psychologist  and  theologian, 
and  the  more  so  since  the  proper  and  profitable  treatment  of  it  becomes 
inseparably  involved  with  things  that  lie  outside  of  his  domain.  • 

Yet  under  these  circumstances,  considering  the  ever-increasing  control 
which  scientific  truth  exerts  over  the  masses  of  men,  considering  too  how 
much  the  welfare  of  the  human  family  depends  on  the  precision  and 
soundness  of  its  religious  views,  it  is  the  duty  of  the  physiologist,  if  for 
the  reasons  that  have  been  specified  he  yields  this  great  subject  to  others, 
to  leave  no  ambiguity  in  the  expression  of  the  conclusion  to  which  his 
own  science  brings  him.  Especially  is  it  for  him,  whenever  the  oppor- 
tunity offers,  to  assert  and  to  uphold  the  doctrine  of  the  oneness,  the  im- 
mortality, the  accountability  of  the  soul,  and  to  enforce  those  paramount 
truths  with  whatever  evidence  the  structure  of  the  body  can  furnish. 

For  this  reason,  he  can  not  recall  but  with  regret  the  existing  use  of 
many  terms,  such  as  mind,  intellect,  vital  principle,  spirit,  which,  though 
they  were  at  first  doubtless  employed  as  expressions  of  the  function's  or 
qualities  of  the  soul,  have  in  the  course  of  time  gathered  other  meanings 
and  confused  the  popular  ideas.  They  have  brought  about  a  condition 
of  things  in  science  not  unlike  that  which  prevailed  in  theology  during 
the  reign  of  polytheism.  Constrained,  perhaps,  himself  by  the  necessities 
of  language  to  use  such  phraseology,  it  is  for  him  at  the  outset  to  leave 
no  doubt  of  the  views  he  entertains,  and,  as  far  as  he  can,  prevent  such 


THE  VITAL  PRINCIPLE.  25 

expressions  from  frittering  away  the  great  truth  that,  as  there  is  but  one 
God  in  the  universe,  so  there  is  but  one  spirit  in  man. 

On  one  of  these  terms,  the  vital  principle,  I  may  make  a  few  remarks, 
since,  from  being  a  mere  expression  of  convenience,  it  has  by  de-  The  vital 
grees  risen  among  physicians  and  physiologists  to  the  rank  of  PrmciPle- 
designating  an  existing  agent,  by  some  regarded  as  of  the  same  kind  as 
light,  heat,  electricity,  or  gravitation — nay,  even  superior  to  them,  since  it 
•  is  its  peculiar  attribute  to  hold  them  all  in  check.  Animated  by  this  ex- 
traordinary power,  organic  substances  are  supposed  to  withstand  every 
external  influence,  and  to  submit  to  physical  agents  only  after  this  prin- 
ciple has  left  them.  Such  a  preposterous  doctrine  will  not  bear  the 
touch  of  exact  science  for  a  moment.  It  is  only  a  relic  of  the  old  meta- 
physical system  of  philosophizing,  which  accepted  a  name  in  lieu  of  an 
explanation,  which  preferred  the  dogma  of  the  horror  of  a  vacuum  to  the 
more  simple  but  material  view  of  the  pressure  of  the  air.  By  the  aid  of 
this  imaginary  principle,  complete  physiological  systems  have  been  wov- 
en, in  which  every  act  and  every  condition  of  the  animal  economy  is  spon- 
taneously explained,  and  nothing  remains  for  solution.  But  by  the  stu- 
dent of  nature,  whose  mind  has  been  trained  in  positive  science,  the  im- 
posture is  detected.  He  sees  at  a  glance  that  this  is  not  the  style  of  the 
Great  Artist.  The  problems  of  organization  are  not  to  be  solved  by  em- 
pirical schemes ;  they  require  the  patient  application  of  all  importance  of 
the  aids  that  can  be  furnished  by  all  other  branches  of  hu- 
man  knowledge,  and  even  then  the  solution  comes  tardily,  ology. 
Yet  there  is  no  cause  for  us  to  adopt  those  quick  but  visionary  specula- 
tions, or  to  despair  of  giving  the  true  explanation  of  all  physiological 
facts.  Since  it  is  given  us  to  know  our  own  existence,  and  be  conscious 
of  our  own  individuality,  we  may  rest  assured  that  we  have  what  is  in 
reality  a  far  less  wonderful  power,  the  capacity  of  comprehending  all  the 
conditions  of  our  life.  God  has  framed  our  understanding  to  grasp  all 
these  things.  For  my  own  part,  I  have  no  sympathy  with  those  who 
say  of  this  or  that  physiological  problem,  it  is  above  our  reason.  My 
faith  in  the  power  of  the  intellect  of  man  is  profound.  Far  from  suppos- 
ing that  there  are  many  things  in  the  structure  and  functions  of  the  body 
which  we  can  never  comprehend,  I  believe  there  is  nothing  in  it  that  we 
shall  not  at  last  explain.  Then,  and  not  till  then,  will  man  be  a  perfect 
monument  of  the  wisdom  and  power  of  his  Maker,  a  created  being  know- 
ing his  own  existence,  and  capable  of  explaining  it.  In  the  application 
of  exact  science  to  physiology,  I  look  for  the  rise  of  that  great  and  noble 
practice  of  medicine  which,  in  a  future  age,  will  rival  in  precision  the  me- 
chanical engineering  of  my  times.  In  it,  too,  are  my  hopes  of  the  final 
K extinction  of  empiricism.  Even  now  this  method  is  attended  with  results 
rhich  must  commend  it  to  every  thoughtful  mind,  since  it  is  connecting 


26  SUBDIVISIONS   OF   PHYSIOLOGY. 

itself  with,  those  great  truths  which  concern  the  human  family  most 
closely,  and  is  bringing  into  the  region  of  physical  demonstration  the  ex- 
istence and  immortality  of  the  soul  of  man,  and  furnishing  conspicuous 
illustrations  of  the  attributes  of  God. 


CHAPTEE  II. 

OF  FOOD. 

The  natural  Subdivisions  of  Physiology. — Of  Food:  its  Sources  and  Classification — its  Value  not 
altogether  dependent  on  its  Composition. — Of  Milk:  its  Composition,  and  Use  of  its  Water, 
Casein,  Sugar,  Butter,  and  Salts. —  Variations  in  the  Composition  of  Milk. — Of  Bread. —  Of 
mixed  Diets. — Of  the  embryonic  Food  of  Birds. — Nutrition  of  carnivorous  and  herbivorous 
•  Animals. — Food  formed  by  Plants  and  destroyed  by  Animals. —  Uses  of  mixed  Food  and  Cook- 
ing.— Absolute  Amount  of  Food. 

PHYSIOLOGY  possesses  a  very  great  advantage  over  many  other  sciences 
Subdivisions  of  in  offering  its  leading  problems  and  doctrines  in  a  certain 
physiology.  well-marked  order  or  sequence,  a  connected  whole,  with  only 
here  and  there  points  of  digression,  but  those  points  often  of  very  striking 
interest.  Thus  pursuing  the  train  of  reflections  entered  on  in  the  pre- 
ceding chapter,  we  should  have  to  consider  the  nature  of  the  food,  the 
manner,  of  its  preparation  by  the  process  of  digestion,  the  mechanism  by 
which  it  is  taken  up  from  the  cavities  in  which  it  has  been  so  prepared, 
and  that  by  which  it  is  distributed  to  every  part.  We  should  have  to 
show  the  way  in  which  it  becomes  incorporated  as  a  portion  of  the  living 
mass,  its  duration  in  that  condition,  and  the  manner  of  its  decay.  We 
should  have  to  show  by  what  physical  means  and  through  what  mecha- 
nism the  air  is  introduced  to  effect  the  destruction  of  the  dying  parts,  and 
how,  as  the  consequence  of  this,  a  fixed  temperature  is  maintained.  The 
causes  which  lead  to  variations  of  this  temperature,  and  the  manner  in 
which  the  wasted  products  are  removed  by  the  skin,  the  lungs,  the  kid- 
neys, might  next  obtain  our  attention.  The  complicated  machinery  nec- 
essary to  accomplish  all  these  purposes  requires  to  be  made  to  act  in  uni- 
son in  all  its  different  parts,  a  condition  which  introduces  to  us  the  nerv- 
ous system.  A  consideration  of  the  structure  and  gradual  development 
of  this  system  leads  to  the  structure  of  the  various  organs  of  sense,  and 
to  the  operations  of  the  intellectual  principle  itself.  Thus  in  succession 
we  should  have  to  treat  of  digestion,  absorption,  circulation,  respiration, 
secretion,  nutrition,  and  innervation,  and  to  close  the  whole  with  the  con- 
sideration of  reproduction.  This  is  the  order  which  I  propose  to  follow, 
and  shall  devote  this  chapter  to  the  nature  and  qualities  of  the  food. 


HISTOGENETIC  AND   CALORIFACIENT   FOOD.  27 

The  supply  of  food  to  animals  requires  a  more  complicated  provision 
than  it  does  to  plants,  in  which  the  elaborating  organs,  the  Sourcesoffood 
leaves,  presenting  themselves  superficially,  are  always  in  for  animals  and 
contact  with  the  air,  from  which  much  of  their  nutrition  is  p  a 
derived.  And  as  one  portion  after  another  becomes  exhausted,  it  is  re- 
newed by  simple  mechanical  agencies,  such  as  the  trembling  of  the  leaf, 
the  warmth  of  the  sun,  or  the  winds. 

Food,  therefore,  comes  spontaneously  to  plants,  which  need  no  powers 
of  locomotion.  And  though,  as  we  shall  hereafter  find,  muscular  move- 
ment requires  as  its  essential  condition  the  waste  of  tissue,  it  is  not  nec- 
essary for  their  nutrition  that  plants  should  destroy  organized  substance. 
But  an  animal  must  seek  its  food,  and  for  this  purpose  is  endowed  with 
locomotion,  involving  the  destruction  of  tissue.  In  a  chemical  point  of 
view,  plants  are  organizing,  and  animals  destroying  machines.  Nor  is 
this  general  assertion  controverted  by  the  apparent  exceptions  which  are 
here  and  there  presented,  as,  for  example,  that  the  herbivora  can  form 
sugar  and  fat  from  food  in  which  those  substances  did  not  pre-exist,  and 
the  salts  of  the  biliary  acids,  which  are  never  found  in  plants. 

To  obtain  for  animals  the  necessary  supply  of  nutriment,  the  resources 
of  nature  are  displayed  in  the  most  wonderful  contrivances.  According 
as  their  modes  of  life  may  be,  one  takes  its  food  with  its  teeth,  another 
with  its  lips,  another  with  its  fore  member,  another  winds  around  it  its 
whole  body.  The  geometrical  spider  weaves  a  net,  and  lies  in  wait  for 
his  prey ;  the  ant  lion  digs  a  pit  in  the  sand.  Some  rely  upon  labor, 
some  upon  force,  some  upon  fraud.  Man  depends  upon  all. 

Viewed  as  regards  its  physiological  distinction,  the  food  is  generally 
considered  as  of  two  kinds :  Histogenetic  or  tissue-making,  and  classification 
Calorifacient  or  heat-making.     Histogenetic  food  furnishes  the  °f  food  int.° 
chemical  substances — carbon,  hydrogen,  oxygen,  nitrogen,  sul-  and°caiorifa- 
phur,  chlorine,  phosphorus,  iron,  potash,  soda,  lime,  &c.     Ca-  cient- 
lorifacient  food  furnishes  carbon  and  hydrogen  mainly.     In  consequence 
of  this  chemical  constitution,  tissue-making  food  is  sometimes  called  ni- 
trogenized,  and  heat -making  non-nitrogenized  food.     The  former  is  also 
sometimes  designated  nutritive,  and  the  latter  respiratory. 

It  is,  however,  to  be  distinctly  understood  that  these  divisions  are  only 
adopted  for  the  sake  of  convenience,  and  that  they  have  no  natural  foun- 
dation. Thus  it  will  be  found,  when  we  examine  the  functions  which 
the  fats  discharge,  that  though  they  are  non-nitrogenized  bodies,  and  are, 
therefore,  considered  as  belonging  to  the  class  of  respiratory  food,  there 
is  every  reason  to  believe  that  they  are  essentially  necessary  to  tissue 
development,  and  that  the  metamorphoses  of  nitrogenized  bodies  can 
only  go  on  in  their  presence.  They  are,  therefore,  as  truly  essential  to 
nutrition  as  are  the  latter  substances. 


28  CLASSIFICATION   OP  FOOD. 

So,  too,  as  respects  the  albumenoid  bodies,  of  which  it  would  be  incor- 
rect to  speak  as  though  they  were  limited  to  nutrition.  In  their  decay 
or  descending  metamorphosis  in  the  organism,  they  give  rise  to  the  evo- 
lution of  heat,  and  are  at  last  dismissed  under  the  aspect  of  products  of 
oxidation.  They  are,  therefore,  as  far  as  this  goes,  as  much  respiratory 
food  as  are  the  fats  themselves. 

Other  ciassifi-  Perhaps  the  most  convenient  subdivision  of  food  articles 
cations  of  food.  js  presented  in  the  four  following  groups : 

1st.  Carbohydrates,  or  compounds  in  which  carbon  is  united  with 
hydrogen  and  oxygen,  their  proportion  being  that  for  forming  water. 
Starch,  sugar,  gum,  cellulose,  are  examples. 

2d.  Hydrocarbons.  Compounds  containing  unoxidized  hydrogen. 
The  oils,  fats,  and  alcohol,  are  examples. 

3d.  Albumenoid  bodies.  These  contain  nitrogen.  Albumen,  fibrin, 
casein,  are  examples. 

4th.  Salts.  Any  classification  of  food  articles  which  does  not  con- 
tain this  group  is  imperfect ;  for  salts  are  not  only  absolutely  essential 
to  organic  processes,  but  also  to  the  construction  of  many  tissues.  As 
an  example  of  the  former  case,  the  chloride  of  sodium  may  be  mentioned ; 
and  of  the  latter,  the  phosphate  of  lime. 

It  has  been  supposed  that  the  tissue-making  power  of  any  kind  of 
Value  of  food  food  depends  on  the  quantity  of  nitrogen  it  contains,  and 
does  not  de-  that  .jfs  value  may  therefore  be  determined  by  chemical  anal- 

pend  wholly  on         .  ^  .         J 

its  composi-  ysis.  Upon  this  principle  tables  have  been  constructed, 
tlon-  showing  the  agricultural  worth  of  different  articles  of  forage 

for  domestic  animals.  But,  as  will  be  found  hereafter,  when  we  consider 
the  physiological  effect  of  the  allotropism  of  bodies,  these  tables  are  not  of 
the  use  supposed.  Without  entering  into  details  at  present,  the  case  of 
gelatin  may  be  taken  as  an  example ;  this,  though  a  substance  abounding 
in  nitrogen,  possesses  no  tissue-making  value,  but  in  reality  belongs  to  the 
calorifacient  class,  and  therefore  its  administration  in  the  sick-room,  under 
the  various  well-known  forms  of  jellies,  soups,  etc.,  is  altogether  deceptive 
as  regards  any  nutritive  power,  since  it  undergoes  speedy  oxidation  in 
the  system,  and  the  products  of  its  change  escape  by  the  kidneys  and  the 
lungs.  The  value  of  food  is  not  only  dependent  on  the  occurrence  of 
certain  chemical  elements ;  they  must  also  be  present  in  certain  allotropic 
states. 

The  same  remark  applies  to  the  tables  which  have  been  constructed, 
showing  the  amount  of  caloric  furnished  by  different  varieties  of  heat- 
making  food.  The  quantity  of  heat  set  free  during  the  combustion  of  a 
substance  depends  not  only  on  the  nature  of  the  elements  composing  it, 
but  also  on  the  particular  states  in  which  they  occur.  Combustibles  may 
have  the  same  chemical  composition,  but  very  different  heating  power. 


COMPOSITION   OF  MILK.  29 

Food  which  is  typically  perfect,  is  presented  by  nature  to  the  young 
of  various  animals.  In  milk,  or  in  the  egg,  we  should  ex-  Miikasanarti- 
pect  to  find  whatever  is  necessary  for  the  growth  of  the  tis-  cic  of  food:  its 

i    f       .1  f  *MI'      *    -   M*  A  composition. 

sues,  and  for  the  performance  01  the  junctions.     An  exam- 
ination of  milk  will  therefore  illustrate  the  essential  characters  of  the 
different  elements  of  food. 

Composition  of  JUiffc. 

Water 873. 

Casein  48. 

Sugar  of  milk 44. 

Butter 30. 

Phosphate  of  lime 2.30 

Other  salts 2.70 

1000.00 

In  this  we  notice,  first,  the  large  proportion  of  water  present,  almost 
nine  tenths  of  the  whole  amount.  The  double  duty  of  this  The  water  of 
water  has  already  been  mentioned,  to  remove  from  the  sys-  milk- 
tern  effete  substances  which  are  not  of  a  vaporous  or  gaseous  form,  and 
which  can  not  escape  through  the  lungs,  and  to  regulate  the  temperature 
by  evaporation.  We  might  have  added  to  these  that  it  imparts  a  due 
fluidity  to  the  blood.  These  are  conditions  as  necessary  to  the  infant 
as  to  the  adult,  and  it  should  be  remembered  that  two  thirds  of  the 
weight  of  the  body  are  water. 

Next  follows  the  nitrogenized  principle  casein,  which  is  closely  re- 
lated in  composition  to  muscular  flesh.  It  is  the  tissue-mak-  The  casein  of 
ing,  histogenetic,  or  nutritive  element  of  the  milk,  and  has  been  milk- 
elaborated  from  the  albumenoid  substances  of  the  mother's  system.  It 
is  to  be  converted  into  the  muscular,  gelatinous,  and  other  soft  tissues  of 
the  infant. 

Casein  is  one  of  a  group  designated  as  the  neutral  nitrogenized  bodies, 
of  which  some  of  the  more  prominent  are  albumen,  fibrin,  Nature  of  pro- 
and  globulin.  From  an  opinion  that  these  all  contain  the  tein  bodies- 
same  organic  radical,  they  are  often  termed  the  protein  bodies.  They 
appear  to  exist  in  two  different  physical  conditions,  soluble  and  insolu- 
ble in  water;  they  all  contain  sulphur,  and  exhibit. a  proneness  to  pass 
into  the  putrefactive  fermentation.  As  this  takes  place  when  they  have 
reached  a  certain  stage  of  decay,  they  act  upon  other  bodies  as  ferments. 
Their  constitution  is  represented  in  common  by  the  formula 

C48  H36  0M  N, 

Of  the  whole  group,  albumen  may  be  taken  as  the  type  and  most  import- 
ant member.     Indeed,  as  will  be  found  hereafter,  in  the  process 
of  digestion  the  others  are  invariably  converted  into  it.     The 
white  of  the  egg  and  the  serum  of  the  blood  are  usually  referred  to  as 
examples  of  albumen,  though  they  differ  in  several  particulars  from  one 


30  CASEIN  AND   FIBEIN. 

another.  Albumen  forms  basic,  neutral,  and  acid  compounds.  It  is  a 
basic  albuminate  of  soda  which  is  found  in  the  egg  and  in  serum  of 
blood.  In  certain  diseased  conditions  the  blood  contains  the  neutral  al- 
buminate. 

Casein  presents  nearly  the  same  constitution  as  albumen,  but  differs 
from  it  in  its  physical  properties ;  for,  while  a  solution  of  albumen 
is  coagulable  by  heat,  one  of  casein  is  not,  but  lactic  and  acetic 
acids  coagulate  it,  -though  they  have  no  such  effect  on  albumen.     While, 
so  far  as  their  protein  nucleus  is  concerned,  the  two  substances  agree  in 
composition,  they  differ  in  this  respect,  that  casein  appears  to  contain  a 
less  proportion  of  sulphur,  and  no  phosphorus.     It  is  interesting  to  re-* 
mark  that,  during  incubation,  casein  arises  from  albumen  in  the  eggs  of 
birds. 

Closely  allied  to  albumen  and  casein,  and  having  the  same  protein  nu- 
cleus, is  fibrin,  which  likewise  exists  in  two  states,  soluble  and 
insoluble.  Its  solidification  or  coagulation  can  be  produced  by 
the  action  of  sulphuric  ether,  which  does  not  affect  albumen.  Moreover, 
in  the  coagulated  state  fibrin  decomposes  the  deutoxide  of  hydrogen, 
but  albumen  does  not.  The  most  important  difference  between  them  is, 
that  in  the  act  of  coagulation  albumen  shows  no  disposition  to  assume  a 
definite  structure,  but  fibrin  does — fibrillating,  as  it  is  termed.  The 
analogy  of  constitution  and  closeness  of  relation  of  the  two  substances  is 
demonstrated  by  the  fact  that  £y  nitrate  of  potash  coagulated  fibrin  may 
be  changed  into  albumen,  and  the  same  conversion  is  accomplished  in  the 
stomach  by  the  digestive  juices. 

It  is»  generally  supposed,  however,  that  fibrin  contains  a  larger  pro- 
portion of  oxygen  than  albumen,  a  conclusion  which  seems  to  be  confirm- 
ed by  physiological  considerations  respecting  its  origin.  For  this  reason, 
Mulder  describes  it  as  a  higher  oxide  of  his  hypothetical  protein.  It  al- 
ways is  associated  with  fat,  or,  perhaps  more  correctly,  with  soaps  of 
ammonia  and  lime.  • 

Fibrin  is  found  in  the  chyle,  lymph,  and  blood.  In  the  latter  fluid 
its  quantity  varies  in  different  parts  of  the  circulation.  The  blood  of  the 
portal  vein  yields  it  in  smaller  proportion  than  that  of  the  jugular.  It  is 
also  affected  very  much  by  diet :  thus  Lehmann  found  that  under  an  ani- 
mal diet  there  was  much  more  fibrin  in  his  blood  than  under  a  vegeta- 
ble one,  a  result  which  has  been  confirmed  by  experiments  on  dogs.  It 
has  also  been  observed  that  its  quantity  is  increased  during  starvation. 
But  the  blood  of  herbivorous  animals  contains  more  than  that  of  carnivo- 
rous ones,  and  that  of  birds  contains  the  most  of  all. 

These  remarks  on  the  composition  and  physical  properties  of  casein, 
albumen,  and  fibrin,  have  been  introduced  for  the  purpose  of  illustrating 
the  facility  with  which  these  bodies  are  mutually  convertible,  and  more 


OF  THE  SALTS,  BUTTEE,  AND  CUED  OF  MILK.          31 

particularly  for  showing  that  there  is  nothing  whatever  mysterious  in 
the  casein  or  curd  of  milk  arising  from  -the  albuminous  serum  of  the 
mother's  blood,  and  being  transmuted  into  the  fibrin  structure  of  the 
muscular  tissues  of  the  infant. 

Returning  now  to  our  examination  of  the  composition  of  milk,  as  set 
forth  in  the  preceding  table,  we  find  that  two  respiratory  el-  The  sugar  and 
ements  are  next  upon  the  list :  1st.  Sugar  of  milk,  which  is  butter  of  milk- 
to  be  converted  into  lactic  acid,  partly  by  the  agency  of  the  saliva,  and 
chiefly  in  intestinal  digestion ;  2d.  Butter,  which  is  the  oleaginous  or 
fatty  portion,  and  of  which  a  part  is  to  be  deposited  in  the  adipose  tis- 
sues for  a  time  of  need,  and  a  part,  along  with  the  lactic  acid  and  excess 
of  sugar,  is  to  be  burned  at  once  for  the  production  of  heat. 

The  inorganic  body,  phosphate  of  lime,  is  necessary  for  the  earthy  por- 
tion of  the  skeleton,  and  probably  the  reason  of  the  introduction  The  ^^  of 
of  casein,  to  the  exclusion  of  other  protein  compounds,  depends  milk,  particu- 
on  the  power  it  possesses  of  holding  phosphate  of  lime  in  solu-  eaSh^nd" 
tion,  not  less  than  6  per  cent,  of  its  weight  of  this  earthy  body  chloride  of  so- 
being  often  obtainable  from  it.     Among  the  other  salts  of 
the  milk,  chloride  of  sodium  may  be  pointed  out  as  of  special  importance. 
It  undergoes  decomposition  in  the  system  of  the  infant,  its  hydrochloric 
acid  giving  acidity  to  the  gastric  juice,  its  soda  entering  into  the  compo- 
sition of  the  bile  and  various  salivary  secretions.     It  also  imparts  solu- 
bility to  albumen,  and,  in  some  degree,  regulates  the  facility  with  which 
that  substance  coagulates.     It  impedes  the  coagulation  of  fibrin. 

Milk  is  not  a  chemical  compound,  but  a  variable  mixture  of  different 
ingredients,  which,  under  proper  circumstances,  may  be  sepa-  Making  of 
rated.  When  the  fluid  is  allowed  to  rest  for  some  hours  at  the  butter- 
ordinary  temperature,  the  fat-globules  rise  to  the  surface  as  cream,  Vhich, 
submitted  to  a  strong  agitation  with  air  in  the  process  of  churning,  forms 
butter. 

The  casein  of  milk  can  be  readily  coagulated  by  rennet  (which  is  the 
mucous  membrane  of  the  stomach  of  the  calf)  at  a  temperature  Making  of 
of  120°.  If  parted  from  the  residual  whey,  mixed  with  a  little  cheese- 
salt  and  yellow  coloring  matter,  and  subjected  to  the  action  of  a  suitable 
press,  it  is  formed  into  cheese.  No  better  examples  of  the  tissue-mak- 
ing and  heat-making  elements  of  food  can  be  offered  than  cheese  and 
butter  respectively. 

When  milk  is  exposed  to  the  air,  its  sugar,  under  the  influence  of  the 
casein  or  curd,  gradually  disappears,  turning  into  lactic  acid,  Lactic  acid  in 
and  the  milk  becomes  sour.  The  composition  of  sugar  and  sour  milk- 
lactic  acid  is  such,  that  we  might,  without  much  error,  say  that  an  atom 
of  sugar  symmetrically  bisected  will  yield  two  atoms  of  lactic  acid.  This 
effect  is  produced  by  the  casein  commencing  to  pass  into  a  state  of  de- 


32  VARIOUS  KINDS  OP  MILK. 

cay  under  the  influence  of  the  atmospheric  air.  It  is  likewise  produced 
during  digestion  by  the  saliva,  and  also  by  the  pancreatic  juice.  The 
turning  sour  of  milk  on  the  stomach  is  due  to  the  transmutation  of  its 
sugar  into  lactic  acid. 

An  infant  finds  in  its  mother's  milk  whatever  it  wants  for  the  growth 
Physiological  of  its  own  body.  In  its  system  the  curd  resumes  the  form 
uses  of  milk.  Of  albumen,  or  passes  into  the  condition  of  fibrin  or  syntonin, 
and  in  this  manner  its  muscular  and  gelatinous  tissues  are  made.  The 
butter  is  deposited  in  the  adipose  cells,  or  burned  at  once  for  the  pro- 
duction of  animal  heat,  a  part  of  it,  however,  being  incidentally  consumed, 
as  will  be  hereafter  explained,  in  the  fabrication  of  fibrin  and  for  other 
histogenetic  purposes.  The  phosphate  of  lime  is  carried  to  the  osseous 
system,  now  in  a  state  of  rapid  increase,  and  bone  is  formed  from  it. 

But  though  milk  is  so  well  adapted  to  the  wants  of  infantile  life,  it  is 
unsuited  to  the  adult.  Its  nitrogenized  principle,  casein,  though  in  suf- 
ficient quantity  for  the  repair  of  muscular  waste  and  development  at  the 
former  period,  is  inadequate  to  these  purposes  at  the  latter,  when  de- 
struction, arising  from  the  incessant  activity  of  the  muscular  system,  is 
V  ri  k*  d  so  grea^7  increased.  It  is  interesting  to  remark  how  the 
of  milk  for  dif-  composition  of  milk  is  modified  when  there  is  a  necessity  to 

nt  animals.  meet  these  indications,  its  nitrogenized  principle  being  in- 
creased in  the  case  of  animals  such  as  the  cow  and  horse,  the  young 
of  which  commence  locomotion  almost  at  birth,  or  at  a  far  earlier  period 
than  the  human  infant.  This  excess  of  casein  is  necessary  for  the  re- 
pair of  the  resulting  waste. 

The  Constitution  of  Mlk. 


Source. 

Casein. 

Sugar. 

Butter. 

Goat's  milk  

80 

40 

40 

Cow's  milk      

63 

28 

40 

32 

36 

29 

This  table  presents  an  explanation  of  the  unsuitableness  which  is 
sometimes  remarked  in  the  milk  of  the  cow  when  used  for  the  nourish- 
ment of  children.  Milk  which  is  adapted  to  the  wants  of  the  calf  is  not 
adapted  to  the  functional  wants  of  the  child.  Experience  has  taught  the 
nurse  that  these  difficulties  may  in  part  be  removed  by  diluting  it  with 
water  and  sweetening  it  with  sugar,  the  effect  of  this  being  to -reduce  the 
percentage  of  the  nitrogenized  element,  the-  casein,  and  to  increase  that  of 
the  respiratory,  and  so  approximate  the  composition  more  closely  to  that 
of  human  milk. 

Moreover,  milk  is  not  suitable  as  the  sole  nourishment  of  adult  life, 
since  it  does  not  contain  in  sufficient  quantity  those  phosphorized  com- 
pounds which  are  necessary  for  the  repair  of  the  waste  of  the  cerebral  and 
nervous  tissues,  which  at  this  period  are  much  more  active  than  in  infancy. 


OF   BREAD. 


33 


Variations  in  the  composition  of  milk  from  its  normal  standard  are  ob- 
served to  depend  upon  age  and  bodily  health.     Young  fe-  influence  of 
males,  from  fifteen  to  twenty,  yield  a  milk  more  rich  in  sol-  ££?&!!& 
ids  than  that  which  is  given  at  thirty-five  or  forty.     Gesta-  sition  of  milk. 
tion  at  a  late  period  increases  the  solid  portions.     The  following  table 
of  Vernois  and  Becquerel  illustrates  the  influence  of  disease : 

• 

Influence  of  Disease  on  the  Constitution  of  Milk. 


In  Health. 

Acute  Disease. 

Chronic  Disease. 

Water  

889.08 

884.91 

885.50 

Casein  and  extractive... 
Sugar  ... 

39.24 
43.64 

50.40 
33.10 

37.06 
43.37 

Butter     

26  66 

29.86 

32.57 

Salts  

1.38 

1.73 

1.50 

1000.00 

1000.00 

1000.00 

From  this  consideration  of  the  nature  and  properties  of  the  food  of  in- 
fancy, we  may  pass  to  the  examination  of  that  of  the  mature  period. 

Experience  has  shown  that,  of  all  articles  of  food,  bread  made  from 
wheaten  flour  meets  best  the  requirements  of  the  adult  life  of 

T,  ^   •        11  ,1     ,   •  f  A     Of  bread. 

man.     It  seems  to  contain  all  that  is  necessary  lor  support.     A 

very  simple  analysis  will  show  how  it  presents  both  the  respiratory  and 

nutritive  elements. 

If  such  flour  be  made  into  a  paste  with  water,  and  be  gradually  washed 
with  a  larger  quantity,  an  elastic  coherent  mass  is  left,  and  Examination 
the  water  assumes  a  milky  turbidity.     After  a  time  it  be-  ^atandof 
comes  clear,  through  the  settling  of  a  white  precipitate,  which  other  grains. 
is  starch,  the  leading  member  of  the  respiratory  group.     The  elastic  sub- 
stance is  gluten,  which  is  a  true  vegetable  fibrin,  mixed  with  another 
nitrogenized  body,  gliadine,  which  may  be  removed,  along  with  a  certain 
quantity  of  oil,  by  washing  with  ether  and  alcohol. 

Thus,  simply  by  washing  in  water,  flour  may  be  separated  into  two 
physiological  elements,  respiratory  and  nutritive,  the  former  being  the 
starch,  and  the  latter  the  gluten.  The  relative  quantity  of  tlicse  substan- 
ces differs  in  different  samples  of  flour,  and,  other  things  being  equal,  the 
greater  the  amount  of  gluten  the  more  valuable  the  sample,  because  the 
more  nutritious.  It  is  interesting  to  remark  that  the  liquid  from  which 
the  starch  has  settled,  if  brought  to  the  boiling  pointy  becomes  turbid 
again,  from  the  coagulation  of  the  vegetable  albumen  it  contains. 

Other  grains,  treated  in  the  same  manner,  yield  similar  results.  The 
flour  of  barley  and  of  the  oat,  when  washed  with  water,  do  not,  however, 
yield  gluten,  but  a  pure  fibrin,  with  a  separation  of  starch. 

The  fibrin  occurring  in  these  grains  is  replaced  in  other  nutritious 
seeds,  such  as  peas  and  beans,  by  legumin,  which,  like  the  casein  of  milk, 
does  not  coagulate  by  boiling,  but  merely  forms  tenacious  skins  as  it  is 
evaporated.  These  may  be  removed  by  skimming.  This  substance, 

C 


34  OF   MIXED   DIETS. 

which  presents  many  analogies  to  casein,  is  coagulable  by  acetic  acid 
and  alcohol,  and,  if  mixed  with  sugar,  turns  curdy,  and  becomes  sour 
from  the  presence  of  lactic  acid.  It  differs  from  casein  in  not  dissolving 
in  concentrated  acetic  acid,  and,  when  precipitated  by  an  acid,  being  un- 
acted on  by  carbonate  of  lime.  It  is,  however,  coagulated  by  rennet. 

Thus,  when  we  use  bread  made  of  any  of  the  common  varieties  of  flour, 
we  find  in  it  both  kinds  of  food,  the  respiratory  and  nutritive — the  former 
as  starch,  and  the  latter  as  fibrin. 

But  civilized  man  has  greatly  improved  on  the  simple  diet  which  Na- 
Use  of  butter  ture  furnishes,  and,  without  knowing  the  immediate  or  philo- 
on  bread.  sophical  reason,  has  added  articles  which  increase  the  respira- 
tory element.  The  proverb  says,  "It  is  good  to  have  bread,  but  it  is 
better  to  have  bread  and  butter."  Let  us  examine  why  it  is  so. 

Wheaten  flour,  in  its  relations  to  the  animal  system,  is  defective  in  one 
point — its  respiratory  element,  the  starch.  Now  the  constitution  of  starch 
is,  that  in  its  dry  state  it  contains  much  more  than  half  its  weight  of  wa- 
ter, none  of  its  hydrogen  being  free,  but  all  oxidized.  It  is,  therefore, 
only  by  the  use  of  very  considerable  quantities  of  bread  that  the  neces- 
sary amount  of  respiratory  food  can  be  had  for  keeping  up  the  tempera- 
ture to  the  proper  degree.  But  if  butter  be  put  upon  the  bread,  the  effect 
is  different.  In  common  with  all  oleaginous  bodies,  butter  contains  an 
excess  of  hydrogen,  and  therefore,  under  the  same  weight,  possesses  a 
very  high  heating  power.  The  defect  of  the  flour  is  thus  compensated, 
and  by  the  use  of  quite  a  moderate  quantity  a  high  temperature  can  be 
maintained. 

It  would  be  very  interesting  to  examine  in  this  way  the  physiological 
relations  of  the  diets  adopted  by  communities  of  men,  and  the  great 
changes  which,  at  quite  a  recent  period,  have  taken  place  through  the  in- 
troduction of  tea,  coffee,  and  chocolate  on  an  extensive  scale  among  civ- 
ilized nations.  Before  the  discovery  of  the  passage  to  the  East  by  the 
Cape  of  Good  Hope,  and  the  establishment  of  direct  commercial  relations 
between  Western  Europe  and  China,  the  general  diet  of  the  agricultural 
classes  consisted  chiefly  of  the  common  products  of  the  farm  and  sub- 
Of  mixed  di-  stances  readily  obtained  in  domestic  economy,  such  as  bread, 
cheese8  and^'  an(l*cheese,  and  beer.  In  a  theoretical  point  of  view,  we  can 
beer.  scarcely  conceive  of  a  diet  more  conducive  to  the  sustenance 

of  the  bodily  frame.  The  constitution  of  wheat  flour  shows  that  it  con- 
tains the  elements  necessary  for  life ;  and  cheese,  which  may  be  regarded 
as  the  preserved  curd  of  milk,  is  an  excellent  flesh-producing  body,  the 
casein  of  which  it  consists  being  readily  convertible  into  muscle-fibrin. 
The  common  salt  used  in  its  preparation  promotes  the  function  of  diges- 
tion, by  furnishing  hydrochloric  acid  and  soda.  In  addition,  there  are 
also  in  the  beer,  an  alcoholic  and  intoxicating  liquid,  all  the  advantages 


EMBRYONIC   FOOD   OF   BIRDS.  35 

of  a  highly  combustible  body  for  the  purposes  of  respiration.  'Whatever, 
therefore,  is  requisite  for  the  well-being  of  the  animal  economy  is  present 
in  abundance  in  such  a  diet. 

From  an  examination  of  the  diet-scales  of  the  educational  and  invalid 
establishments  of  London,  the  prisons  and  the  hospitals,  Beneke  obtains 
the  result  that  the  nitrogenized  should  be  to  the  non-nitrogenized  food  in 
weight  as  one  to  five.     From  other  data,  Frerichs  calculates  Ratio  of  nitro- 
that  the  diurnal  consumption  should  be  2.17  oz.  avoirdupois  non-ntoo"en- 
of  nitrogenized,  and  15.54  oz.  avoirdupois  of  non-nitrogen-  izedfood. 
ized  food,  that  is,  about  as  one  to  seven.     Whatever  is  taken  more  than 
this  is  superfluous. 

The  peculiar  advantages  arising  from  the  use  of  casein,  which  in  a  solu- 
ble form  possesses  the  quality  of  dissolving  large  quantities  of  phosphate 
of  lime,  unquestionably  determine  its  employment  as  a  constituent  of 
milk.  But  there  are  circumstances  under  which  a  necessity  arises  for 
the  use  of  other  nitrogenized  compounds,  such  as  albumen,  in  early  nu- 
trition ;  and  then  it  is  remarkable  by  what  indirect  methods  the  difficulty 
of  its  want  of  solvent  power  over  that  earthy  body  is  compensated  for. 
The  foetal  period  of  the  life  of  birds  furnishes  an  example.  In  the  egg 
there  is,  of  course,  whatever  is  wanted  for  the  development  Development 
of  the  young  animal ;  for,  merely  by  the  process  of  incuba-  th*e»g^ori"in 
tion,  or  submitting  the  egg  to  a  due  temperature  for  a  suita-  of  its  parts. 
ble  length  of  time,  with  the  access  of  atmospheric  air,  the  young  chicken 
forms,  with  all  its  parts  complete — its  bony,  muscular,  nervous  systems, 
feathers,  beak,  claws.  The  phosphate  of  lime  required  for  the  skeleton 
is  not  present  as  such,  but  is  formed  as  incubation  goes  on ;  for  in  the 
yolk  there  is  free  phosphorus,  to  which  the  air  finds  access  through  the 
pervious  shell,  and,  effecting  its  oxidation,  phosphoric  acid  is  the  result. 
This  reacts  on  the  "carbonate  of  lime,  of  which  the  shell  consists,  decom- 
poses it,  and  the  phosphate  of  lime  forms.  For  this  reason  we  observe, 
as  the  incubation  proceeds,  that  the  shell  becomes  lighter  and  thinner. 
The  albuminous  fluid  which  constitutes  the  white  of  the  egg  has  little 
power  of  holding  bone-earth  in  solution  ;  but  by  manufacturing  the  salt 
in  this  manner,  as  it  is  wanted,  the  development  of  the  young  bird  goes 
on  without  difficulty.  To  insure  the  due  supply  of  oxygen,  an  air-bub- 
ble is  placed  at  the  broad  end  of  the  egg,  so  that,  should  any  transient 
circumstance  interfere  with  the  passage  of  air  through  the  pores  of  the 
shell,  there  is  a  little  reservoir  of  that  material  on  which  to  rely. 

The  mammalia  find  in  milk  all  that  they  need  in  their  infantile  life 
for  their  nutritive  purposes.  In  the  same  manner  birds,  in  their  foetal 
life,  have  whatever  they  require  in  the  egg.  For  the  former,  casein  is 
the  nutritive  element ;  for  the  latter,  albumen.  In  both  cases  a  ready 
transmutation  of  that  element  into  muscle-fibrin  occurs. 


36  FOOD  OF  CAENIVORA  AND  HERBIVORA. 

At  a  mtiturer  period  of  life,  animals  may  be  divided  into  two  groups, 
carnivorous  and  herbivorous,  or  those  which  feed  exclusively  on  flesh, 
and  those  which  feed  on  vegetable  substances.  Between  these  may, 
perhaps,  be  introduced  a  minor  group,  partaking  of  the  manner  of  life  of 
both. 

The  carnivorous  animal  finds  in  its  prey  all  that  is  'required  for  nutri- 
Nutrition  of  tion'  anc*  t^ie  discharge  °f  its  functions.  Digestion  under  these 
carnivorous  circumstances  is  reduced  to  its  simplest  conditions,  and  is 
a  s>  scarcely  more  than  a  process  of  solution.  In  the  stomach  the 
fibrin  is  brought  into  a  soluble  form ;  in  the  duodenum  the  fats  are  re- 
duced to  an  emulsion.  The  digestive  apparatus  has  but  little  complexi- 
ty. The  stomach  maybe  regarded  as  a  mere  enlargement  or  pouch  upon 
the  alimentary  canal,  having,  along  with  the  intestine,  the  office  of  bring- 
ing the  food  into  such  a  condition  that  it  can  be  taken  up  by  the  veins 
and  lacteals,  and  so  pass  into  the  circulation.  The  various  constituents 
now  revert  into  the  same  state  in  which  they  were  before  digestion  be- 
gan, the  fibrin  aiding  in  the  repair  of  the  wasted  muscular  tissues,  and 
the  fats  being  deposited  in  the  adipose  cells.  The  bones,  feathers,  and 
other  such  matters  as  have  not  been  dissolved  by  digestion,  are  cast  out. 

In  the  production  of  heat  and  motion  the  carnivorous  animal  consumes 
itself,  and,  through  the  oxidation  incessantly  going  on  by  means  of  the 
air  introduced  by  respiration,  carbonic  acid,  ammonia,  water,  sulphuric 
and  phosphoric  acids  are  constantly  forming. 

On  a  superficial  view  it  might  be  supposed  that  in  the  other  group, 
Nutrition  of  ^e  h^ivorous,  *ne  case  *s  quite  different.  These  seem  to 
herbivorous  spend  all  their  lives  in  obtaining  food.  The  ox  or  the  horse, 
put  out  into  the  pastures,  is  all  the  day  long  cropping  the 
grass.  On  a  comparison  of  the  quality  and  nature  of  the  food  which 
they  take  with  the  substances  of  which  their  bodies  consist,  there  seems 
to  be  nothing  in  common.  It  was  not,  therefore,  without  reason  that  the 
earlier  physiologists  imputed  to  the  digestive  organs  of  this  class  the 
power  of  forming  flesh  and  blood  from  vegetable  matters.  When,  how- 
ever, we  come  to  a  critical  examination  of  the  facts,  we  find  that  there  is 
no  essential  difference  between  them  and  the  carnivora. 

When  the  expressed  juice  of  vegetables  is  permitted  to  stand  for  a 
time,  though  it  may  have  been  clear  at  first,  a  turbidity  sets  in,  and  a  flaky 
material  is  deposited.  The  substance  thus  possessing  the  power  of  spon- 
taneous coagulation  is  identical  in  that  property,  and  in  composition,  with 
animal  fibrin.  After  its  deposit,  if  the  clear  liquid  be  warmed  to  near  the 
boiling  point,  it*  again  becomes  turbid,  and  a  second  nitrogenized  sub- 
stance subsides,  which,  from  its  quality  of  coagulating  by  rise  of  tempera- 
ture and  its  analysis,  is  inferred  to  be  identical  with  animal  albumen. 
When  this  has  been  separated  by  filtration  or  otherwise,  and  the  juice  is 


NUTRIENT   MATTERS   PEE-EXIST   IN   PLANTS.  37 

slowly  evaporated,  there  come  on  its  surface  skins  of  a  body  having  the 
same  qualities  as  casein ;  so  fibrin,  albumen,  and  casein  pre-exist  in  plants. 

Fatty  matters  of  every  description  may  also  be  extracted  from  vege- 
table products.  From  leaves,  seeds,  bark,  wood,  etc.,  oleaginous  bodies 
can  be  obtained  by  the  action  of  sulphuric  ether,  which  removes  the  fat, 
and  leaves  it  on  subsequent  evaporation. 

It  being  thus  understood  that  the  food  of  the  graminivorous  animals 
contains  nitrogenized  bodies  and  fats  ready  formed,  we  have  clearer  views 
of  the  function  of  digestion  in  those  tribes.  It  is  not  necessary  to  im- 
pute to  their  digestive  organs  the  power  of  creating  flesh  and  fat  from 
vegetable  matter.  The  office  of  the  animal  is  merely  to  collect.  The 
two  groups  being  compared  together,  the  carnivorous  animal  receives  un- 
der less  compass  the  required  amount  of  nutrition,  and  its  digestive  ap- 
paratus is  more  compact.  But  the  graminivorous  animal  must  all  the 
day  long  collect  large  quantities  of  food,  out  of  which  it  may  extract  the 
little  nutrient  matter  they  contain.  The  carcass  of  an  animal,  seized  by 
a  lion,  is  almost  all  digestible,  but  it  would  require  a  very  large  amount 
of  herbage  or  of  grain  to  be  supplied  to  an  ox  to  make  up  the  same  quan- 
tity of  albumen  .or  fat.  Hence  the  necessary  complexity  and  size  of  the 
digestive  organs  of  the  herbivorous  group,  and  hence  many  of  their  hab- 
its of  life. 

Moreover,  we  see  that  even  in  this  apparently  extreme  case  the  ani- 
mal system  does  not  clearly  exhibit  any  quality  of  exerting  Food  formed 
a  formative  action,  nor  of  grouping  atoms  into  a  state  of  Destroyed  by* 
higher  organization.     It  possesses  no  special  power  of  mak-  animals, 
ing  flesh.     To  the  vegetable  world  we  have  to  look  as  the  great  forma- 
tive agent.     In  the  organism  of  plants  the  various  compounds  wanted 
by  animals  are  fabricated.     Animals  destroy  those  compounds,  and  in 
so  doing  maintain  a  high  temperature,  irrespective  of  atmospheric  con- 
ditions, and  give  rise  to  the  phenomena  of  motion  and  intellectuality. 

Universal  experience,  as  well  as  direct  experiment,  proves  that  in  the 
case  of  man  health  can  not  be  maintained  on  a  uniform  diet,  however  it 
may  be  with  animals.  A  mixed  food,  which  varies  from  time  to  time, 
seems  to  be  essential;  and  there  can  not  be  a  doubt  that  the  changes 
which  physicians  have  recognized  in  the  nature  of  the  predominating  dis- 
eases, from  century  to  century,  are  connected  with  changes  which  have 
taken  place  in  the  nature  of  the  diet.  The  introduction  of  tea,  coffee, 
the  potatoe,  arid  tobacco,  must  have  made  a  marked  impression  in  these 
respects. 

Undue  excesses  of  albumen,  oil,  or  starch,  in  the  diet  of  an  individual, 
produce  a  liability  to  arthritic,  bilious,  and  rheumatic  affec-  Necessity  of  a 
tions.  An  abstinence  from  fresh  vegetables  and  fruits  devel-  ^an^us? * 
ops  scorbutic,  and  a  deficiency  of  oleaginous  materials  scrofu-  of  cooking. 


38  ABSOLUTE  QUANTITY  OF  FOOD. 

lous  disease.  It  is  evident  that  a  control  over  these  affections  may  be  ob- 
tained, or  even  their  cure,  to  a  considerable  extent,  accomplished,  by  suit- 
able changes  in  the  nature  of  the  food.  This  is  strikingly  seen  in  the 
improvement  of  the  health  of  sailors  during  long  voyages,  since  the  intro- 
duction of  vegetable  preparations  or  acid  juices.  In  1726,  Admiral  Ho- 
*  sier  sailed  from  England  to  the  West  Indies  with  seven  ships  of  the 
line,  and  lost  his  whole  crew  twice  by  scurvy.  The  circumnavigation 
of  the  globe  is  now  often  accomplished  without  the  loss  of  a  single  man. 

I  have  already  remarked  the  insufficiency  of  the  tables  setting  forth 
the  value  of  articles  of  food  as  dependent  on  their  chemical  constitution. 
Such  tables  are  of  little  use,  agriculturally,  in  the  case  of  animals,  and 
still  less,  physiologically,  in  the  case  of  man.  The  art  of  cooking  does 
not  minister  alone  to  the  gratification  of  the  palate,  it  lends  a  real  assist- 
ance to  the  operation  of  digestion.  New  elements  may  not  have  been 
added,  nor  existing  ones  removed  in  submitting  the  food  to  the  action 
of  a  high  temperature,  yet  such  a  change  is  thereby  impressed  upon  it 
that  it  becomes  more  capable  of  digestion,  and  more  subservient  to  the 
wants  of  the  economy. 

In  determining  the  absolute  quantities  of  nutrient  substances  required 
The  absolute  ^7  *ne  system,  Lehmann  observes  that  there  are  three  mag- 
quantity  of  nitudes  which  we  are  especially  called  upon  to  consider :  the 
first  is,  the  quantity  of  food  requisite  to  prevent  the  animal 
sinking  from  starvation  ;  the  second  is,  that  which  affords  the  right  sup- 
ply of  nourishment  for  the  perfect  accomplishment  of  the  functions  ;  and 
the  last  is,  that  which  indicates  the  amount  of  nutrient  matter  which 
may,  under  the  most  favorable  circumstances,  be  subjected  to  metamor- 
phosis in  the  blood.  The  method  of  finding  the  minimum  of  food  nec- 
essary to  support  life  by  stopping  all  supplies  without,  and  determining 
the  quantities  of  matters  which  the  organism  uses  by  the  excretion  of 
urine,  fasces,  expired  and  transpired  products,  though  it  has  yielded  re- 
sults of  the  utmost  importance  to  science,  is  nevertheless  not  altogether 
reliable,  for  in  such  a  state  of  inanition  the  system  is  brought  into  a 
morbid  condition,  or,  at  all  events,  is  not  acting  in'a  normal  way.  More- 
over, much  depends  on  the  activity  with  which  the  various  functions  are 
carried  forward,  a  necessity  for  nourishment  increasing  with  increase  of 
external  activity.  And  as  to  the  amount  of  food  demanded  for  the 
maintenance  of  the  system  at  its  standard,  it  must  be  borne  in  mind 
that  of  the  four  classes,  the  carbohydrates,  the  fats,  the  albuminous  mat- 
ters, and  the  salts,  no  one  alone  will  answer  the  purpose,  but  all  must 
be  employed  together,  and  this  in  variable  proportion,  according  as  the 
local,  and  therefore  variable,  wastes  of  the  system  may  have  been.  These 
considerations  indicate  how  complicated  the  problem  we  have  in  view 
really  is. 


QUANTITY   OF   FOOD   REQUIRED.  39 

From  the  experiments  of  Boussingault  with  reference  to  fat,  and  of 
Bidder  and  Schmidt  with  reference  to  the  albuminates,  and  Maximum  lim- 
of  Yon  Becker  with  reference  to  the  carbohydrates,  we  learn  J^SStS 
that  only  definite  quantities  of  these  substances  can  be  ab-  mentsoffood. 
sorbed  by  the  intestine  in  definite  periods  of  time.  This  maximum  limit 
is,  however,  far  more  than  the  necessities  of  the  system  require ;  hence  in 
overfeeding,  though  much  of  the  excess  of  food  passes  away  with  the  ex- 
crement, a  very  large  portion  is,  as  it  were,  needlessly  absorbed,  and,  un- 
dergoing metamorphosis  in  the  blood,  is  removed  by  the  kidneys.  To 
this  portion  Lehmann  applies  the  designation  introduced  by  Schmidt, 
luxus  consumption,  or  superfluous  consumption.  Of  course,  the  simplest 
condition  under  which  we  can  investigate  the  normal  quantity  of  food 
required  is  that  of  an  invariable  weight,  and  the  difficulties  of  the  inquiry 
are  increased  when  growth,  corpulence,  pregnancy,  or  other  such  states, 
are  included. 

Though  we  are  very  far  from  being  able  to  offer  a  complete  solution 
of  the  problem  of  the  amount  of  food  required,  in  its  most  general  sense, 
yet,  through  the  labors  of  many  chemists,  we  have  accumulated  several 
facts  which  have  a  bearing  on  this  question.  Thus  it  is  known  that  albu- 
minous substances  alone  can  not  be  absorbed  in  quantity  enough  to  com- 
pensate for  the  loss  of  carbon  by  respiration.  A  duck,  as  is  shown  by 
Boussingault,  expires  in  one  hour  1.25  grammes  of  carbon,  but  can  only 
absorb  of  carbon  in  albuminates  1. 00  gramme.  So,  in  like  manner,  fat  alone 
is  inadequate,  for  of  this  substance  0.84  gramme,  containing  about  0.70 
gramme  of  carbon,  can  only  be  taken  up  in  an  hour,  and  this  is  not  much 
more  than  half  of  what  the  respiratory  operation  demands.  The  carbo- 
hydrates, however,  can  be  absorbed  in  sufficient  proportion,  and  in  this 
mixed  manner  are  all  the  requirements  satisfied.  Boussingault  makes 
the  curious  remark  that,  in  the  quantity  of  starch,  5.26  parts,  and  the 
quantity  of  sugar,  5.62  parts,  which  this  bird  can  absorb  in  one  hour, 
there  are  nearly  the  same  quantities,  2.37,  of  carbon. 

Among  the  special  investigations  which  have  been  made  to  determine 
the  amount  of  food  used  and  the  amount  of  educts  from  the  Amount  of 
system,  should  be  mentioned  that  of  Valentin  upon  himself,  food,  and 
His  weight  was  117  Ibs. ;  his  diurnal  consumption  of  food, 
6.451  Ibs.;  solid  excrement,  .42  lb.;  urine,  4.686  Ibs.;  and  2.751  Ibs. 
perspiration.     From  the  more  recent  and  very  exact  experiments  of  Bar- 
ral,  it  is  inferred  that  of  100  grammes  of  carbon  which  have  been  ab- 
sorbed into  the  organism,  91.59  escape  as  carbonic  acid  through  the  lungs 
and  skin,  4.58  appear,  in  the  urine,  and  3.83  are  re-excreted  and  appear 
in  the  fasces.      Upon  similar  principles,  Lehmann  computes,  from  the 
data  furnished  by  Barral,  that  for  every  100  parts  of  absorbed  nitrogen, 
49.6  parts  are  removed  through  the  skin  and  lungs,  42.07  are  found  in 


40  OF   DIGESTION. 

the  urine,  and  8.33  are  re-excreted  into  the  faeces.  As  a  general  result, 
it  follows,  from  these  experiments,  that  an  adult  man  oxidizes,  on  an 
average,  289  grammes  of  carbon,  and  18.6  grammes  of  hydrogen  in 
twenty-four  hours. 


CHAPTER  III. 

OF  DIGESTION. 

TISSUE-MAKING   OR   HISTOGENETIC   DIGESTION. 

Nature  of  Digestion. — The  Mouth,  Teeth,  Stomach. — The  Salivary  Glands. — Different  Kinds  of 
Saliva. — Properties  of  mixed  Saliva :  its  Quantity,  Composition,  and  Functions. — Relation  of 
the  Salivary  Glands  and  Kidneys. — The  digestive  Tract. — The  Stomach. — Gastric  Juice. — 
Organs  for  its  Preparation. — Manner  of  producing  Chyme. — Influence  of  the  Nerves. — Artifi- 
cial Digestion. — Preparation  and  Properties  of  Pepsin. — Regional  and  functional  Divisions  of 
the  Stomach  in  Animals  and  in  Man. — Object  of  Stomach  Digestion. — Peptones. —  Use  of  Salt. 
— Digestibility  of  various  Articles  of  Food. 

BEFORE  the  food  can  be  absorbed  and  carried  to  all  parts  of  the  sys- 
Nature  of  tem  it  must  be  submitted  to  certain  preparatory  operations, 
digestion.  ginCe  it  is  either  to  be  dissolved  in  the  blood  or  transported  as 
chyle  through  the  lacteal  vessels,  it  is  absolutely  necessary  to  bring  it 
into  a  condition  of  solution  in  water,  or  at  least  into  a  state  of  minute 
suspension  in  that  liquid.  Eeceived  in  masses  of  a  certain  size,  it  is 
first  cut  and  crushed  into  smaller  portions  by  the  teeth,  and  then  brought 
from  an  insoluble  into  a  soluble  or  suspended  state  by  the  chemical  ac- 
tion of  the  digestive  juices. 

In  the  mouth  the  food  is  submitted  to  a  twofold  preparation.  It  is 
Functions  of  divided  by  the  mechanical  action  of  the  teeth,  and  also  simul- 
the  mouth,  taneously  mingled  with  liquids  secreted  from  the  salivary 
glands. 

The  animal  series  present  us  with  numberless  contrivances  for  accom- 
plishing this  comminution.  The  teeth,  though  of  a  bony  nature,  are  not 
to  be  regarded  as  appertaining  to  the  skeleton,  but  rather  to  the  digestive 
mechanism.  Their  structure,  number,  and  position  differ  veiy  much  in 
different  tribes.  In  certain  fishes  the  mouth  is  almost  lined  with  them. 
In  crabs  they  extend  to  the  stomach,  but  in  other  cases  they  are  restrict- 
ed to  the  pharynx,  or  are  wholly  absent ;  this  being  the  case,  for  instance, 
among  the  ant-eaters.  Those  insects  whose  food  is  of  a  fluid  nature  have 
Instruments  of  no  need  of  teeth ;  but  those  which  use  solid  material  are  ac- 
in^ariou^ani-  comm°dated  with  suitable  instruments  of  abrasion,  such  as 
mals.  borers,  chisels,  saws,  nippers,  the  particular  mechanism  re- 


THE  TEETH.  41 

sorted  to  being  adapted  to  the  nature  of  the  food.  It  is  to  be  understood 
that  these  mechanical  terms  are  not  mere  metaphors,  they  indicate  the 
actual  nature  of  the  apparatus.  The  object  aimed  at  is  to  obtain  the  food 
in  such  small  portions,  and  in  such  a  bruised  or  pulpy  condition,  that  di- 
gestion can  be  accomplished  promptly.  In  man  the  number  of  _ 

,    .          r  r  .      ^    ;    .  m  T    The  teeth. 

temporary  teeth  is  twenty,  ten  in  each  jaw.     They  are  arranged 
in  three  classes — four  incisors,  two  canines,  and  four  molars  for  the  up- 
per and  under  jaw  respectively.     The  permanent  teeth,  which  are  eventu- 
ally substituted  for  these  temporary  ones,  are  thirty-two  in  number,  class- 
p.  1  ified  for  each  jaw  as  four  incisors,  two  ca- 

nines, four  bicuspids,  and  six  molars. 
Their  arrangement  is  exemplified  in  Fig. 
1,  representing  the  lower  jaw,  in  which 
i  is  the  middle  and  lateral  incisor,  c  the 
canine,  b  the  two  bicuspids,  and  m  the 
three  molars. 

The  movements  of  the  teeth,  aided  by 
those  of  the  tongue,  accomplish  a  due 
abrasion  of  the  food,  and  simultaneously 

The  human  lower  jaw.  .  .  _.  .      . 

incorporate  it  with  the  saliva,      llus  is, 

therefore,  a  purely  mechanical  operation.  It  is  analogous  to  Mechanical  na_ 
the  methods  to  which  chemists  resort  in  their  laboratories  ture  of  mastica- 
when  they  prepare  solid  materials  for  exposure  to  reagents. 

The  mingling  of  food  with  saliva,  or  insalivation,  effects  a  double  ob- 
ject. Coated  over  with  a  glairy  juice,  the  bruised  substance  passes 
along  the  resophageal  tube  into  the  stomach ;  but  there  are  also  certain 
chemical  changes,  which,  commencing  in  the  mouth,  are  of  essential  im- 
portance to  the  completion  of  digestion. 

The  stomach  is  an  expansion  of  the  alimentary  canal  between  the 
oesophagus  and  duodenum,  of  a  conical  figure,  the  base  of  Description  of 
which  is  to  the  left.  It  communicates  with  the  oesophagus  the  human 
by  its  cardiac  orifice,  and  by  its  pyloric  with  the  duodenum. 
It  consists  of  three  coats  or  tunics  —  the  serous  or  peritoneal,  which  is 
exterior ;  the  muscular,  which  is  intermediate ;  and  the  mucous,  which  is 
interior.  They  are  connected  with  each  other  by  cellular  tissue.  The 
fibres  of  the  muscular  coat  run  in  three  different  directions,  constituting 
three  layers ;  the  superficial  ones  are  longitudinal,  radiating  from  the  oesoph- 
agus over  the  surface  of  the  organ ;  those  of  the  middle  layer  are  circular, 
or  ring-like ;  they  are  well  developed  about  the  middle  of  the  stomach, 
and  by  their  contractions  sometimes  make  it  assume  a  divided  appear- 
ance, as  though  composed  of  two  compartments.  Toward  the  pylorus 
they  are  also  greatly  re-enforced.  The  fibres  of  the  third  layer  take,  for 
the  most  part,  an  oblique  direction.  The  interior  or  mucous  coat  is  some- 


42  THE   STOMACH^ 

times  termed  the  villous,  from  its  velvety  appearance.  Its  color  is  very 
variable ;  it  is  folded  into  rugas,  which  admit  of  variations  in  the  disten- 
tion  of  the  stomach,  without  interference  with  the  structure  or  functions 
of  the  membranes  of  which  they  are  a  part.  The  cardiac  orifice  is  pli- 
cated, and  the  opening  into  the  duodenum  is  through  a  circular  fold  with 
a  central  aperture — the  pyloric  valve,  which  being  surrounded  with  a 
band  of  muscular  fibres,  acting  as  a  sphincter,  the  passage  from  the  stom- 
ach to  the  intestine  may  be  entirely  obstructed. 

The  stomach  is  seen  in 
section  Fig.  2,  a  being  the 
oesophagus ;  b,  the  greater 
extremity ;  c,  the  smaller 
curvature;  d,  the  great 
curvature;  e,  the  pyloric 
or  less  end ;  /,  A,  the  du- 
odenum ;  <7,  place  of  entry 
of  the  ductus  communis 
choledochus  and  pancre- 
atic duct.  The  place  of 

Section  of  the  human  stomach  showing  its  mucous  interior.  J 

is  the  cardiac  region:  the 

membrane  is  there  plicated.  The  place  of  junction  of  the  duodenum  is 
the  pyloric  region.  , 

The  typical  form  of  the  digestive  apparatus  is  a  sac  with  one  aperture, 
Types  of  the  winch  serves  the  double  purpose  of  affording  an  entrance  to 
stomach.  nutritive  material,  and  an  outlet  to  undigested  remains.  In  a 
higher  condition  it  may  be  conceived  of  as  a  tube  open  at  both  ends,  and 
having  a  sac-like  swelling  on  its  middle  part.  The  portion  of  the  tube 
anterior  to  the  sac  is  the  type  of  the  oesophagus,  its  aperture  answering 
to  the  mouth,  the  sac-like  swelling  being  the  type  of  the  stomach,  and  the 
tube  leading  from  it  representing  the  intestinal  canal.  In  the  more  ele- 
mentary of  such  forms,  vessels  arise  from  the  walls  of  the  digestive  cav- 
ity, and  pass  to  all  other  parts  of  the  system.  These  serve  to  convey  the 
elaborated  material.  Certain  appendages  are  soon  to  be  discovered  in 
connection  with  this  simple  digestive  mechanism.  They  are  for  the 
preparation  of  salivary,  gastric,  pancreatic,'  or  biliary  juices.  In  size  or 
development  they  vary  with  the  habits  of  life  of  the  animal,  or  with  the 
nature  of  its  food.  Indeed,  the  same  remark  may  be  made  as  respects 
the  entire  digestive  tract  of  the  highest  tribes.  Thus,  in  the  bat  the 
length  of  the  intestine  is  to  that  of  the  body  as  three  to  one,  but  in  the 
sheep  as  twenty-eight  to  one.  The  ruminants  generally  have  an  intes- 
tinal tube  of  great  length.  In  man  and  in  monkeys  the  proportion  is 
about  five  or  six  to  one.  Again,  as  regards  construction,  there  are  many 


DIFFERENT   KINDS   OF  SALIVA.  43 

diversities,  the  number  of  digestive  dilatations  and  their  size  correspond- 
ing in  some  measure  to  the  nature  of  the  food. 

Three  pairs  of  glands,  the  parotid,  submaxillary,  and  sublingual,  se- 
crete saliva.  Of  these  organs  the  parotid  is  the  largest ;  its  Different  kinds 
secretion  is  delivered  through  the  duct  of  Steno.  The  sub-  of  saliva- 
maxillary  duct  is  Wharton's,  but  the  sublingual  pours  its  fluid  through 
many  small  apertures  near  the  frenum  linguae  Besides  these  proper  sali- 
vas, the  lining  membrane  of  the  mouth  yields  a  fluid,  the  buccal  mucus. 

The  parotid  saliva  is  thin  and  watery,  limpid  and  colorless,  inodorous 
and  tasteless.  Secreted  during  fasting  or  under  the  use  of  The  parotid  sa- 
stimulating  food,  it  is  denser.  It  contains  so  large  a  quanti-  liva- 
ty  of  lime  that,  on  exposure  to  the  air,  it  becomes  covered  with  an  in- 
crustation of  the  carbonate  of  that  substance.  It  also  contains  sulpho- 
cyanide  of  potassium.  Its  organic  ingredient,  if  not  albuminate  of  soda, 
closely  resembles  that  body. 

From  the  chemical  constitution  of  the  saliva  of  the  parotids,  the  phys- 
iological function  of  those  glands,  as  aquiparous  organs,  is  established. 
They  yield  a  certain  quantity  of  watery  juice,  which,  by  reason  of  its 
thinness  or  fluidity,  is  readily  incorporated  with  the  food  by  the  teeth. 
Parotid  saliva  appears  to  have  no  power  of  transmuting  starch  into  sugar. 

The  submaxillary  saliva  is  also  colorless  and  limpid,  tasteless  and  in- 
odorous. It  contains  no  morphological  elements.  It  is  The  submaxil- 
lighter  than  the  parotid,  less  alkaline,  and  contains  less  lime.  lair  saliva. 
For  this  reason,  when  exposed  to  the  air,  it  does  not  become  incrusted 
with  carbonate  of  that  earth.  It  contains  sulphocyanide  of  potassium. 
It  is  so  viscid  and  glutinous  that  it  may  be  drawn  into  threads.  From 
this  physical  property  it  probably,  facilitates  deglutition  by  furnishing  a 
kind  of  anti-friction  coating. 

The  .sublingual  saliva  is  thin  and  watery,  containing,  like  the  parotid, 
but  a  small  percentage  of  solid  matter,  and  probably  dis-  The  sublingual 
charging  a  similar  function.  •  saliva. 

Besides  the  special  salivary  juices,  the  lining  membrane  of  the  mouth 
pours  forth  a  liquid — the  buccal  mucus — a  thick  and  tena-  The  buccal  mu- 
cious  substance,  having  many  epithelial  cells.  It  is  alkaline  cus- 
in  its  reaction,  does  not  coagulate  on  heating,  its  insoluble  salts  contain- 
ing no  carbonate  of  lime.  It  has  been  obtained  for  examination  by  tying 
the  ducts  of  Steno  and  Wharton,  keeping  the  nostrils  open  and  the  head 
inclined,  so  that,  the  animal  being  unable  to  swallow,  the  mucus  flows  out 
of  the  mouth. 

The  buccal  mucus,  if  mixed  with  parotid  saliva,  does  not  appear  to 

)ssess  the  power  of  turning  starch  into  sugar,  but,  if  mixed  with  the 
submaxillary  secretion,  it  accomplishes  that  transmutation  with  facility. 

The  saliva,  as  obtained  from  the  mouth,  is  therefore  a  mixture  of  the 


44  PROPERTIES   OF   MIXED  SALIVA. 

secretions  of  the  various  salivary  glands.  It  may  be  doubted  whether 
Properties  of  the  method  of  obtaining  it  sometimes  recommended,  by  mak- 
mixed  salivas.  jng  pressure  under  the  chin  and  tickling  the  fauces  with  a 
feather,  yields  it  of  normal  constitution.  It  is  described  as  an  alkaline 
juice,  of  a  bluish  color  or  colorless,  in  consistency  glairy,  readily  froth- 
ing, and  therefore  well  adapted  for  entrapping  atmospheric  air.  It  con- 
tains, of  solid  matter,  from  0.348  to  0.841  per  cent.  Its  alkali  appears, 
for  the  most  part,  to  be  combined  with  an  organic  substance,  ptyaline, 
from  which  it  may  be  separated  by  the  weakest  acids,  such  as  carbonic. 
In  the  ash  of  saliva  the  alkali  occurs  chiefly  as  phosphate :  this  arises  from 
rearrangement  of  the  constituents  during  incineration.  The  saliva  con- 
tains but  a  trace  of  alkaline  sulphates,  the  chlorides  of  sodium  and  potas- 
sium preponderating  over  all  the  other  mineral  ingredients. 

On  standing,  saliva  separates  into  two  layers :  a  transparent  one,  which 
is  supernatant,  and  a  grayish  turbid  one  below,  which  consists  of  a  de- 
posit of  particles  of  pavement  epithelium  and  mucus  corpuscles,  derived 
from  the  lining  membrane  of  the  mouth  and  the  salivary  ducts.  Its 
chemical  reaction  varies  to  some  extent  with  the  state  of  the  system ;  thus, 
after  long-continued  fasting,  from  being  alkaline,  it  may  approach  the  neu- 
tral state.  By  some  it  is  asserted  that  under  these  conditions  it  may 
even  become  acid.  There  is  no  proof  that  this  is  owing  to  the  appear- 
ance of  lactic  acid :  it  may  be  due  to  butyric  acid,  or  even  the  acid  phos- 
phate of  soda.  In  morbid  conditions  this  reaction  is  by  no  means  infre- 
quent :  it  has  been  commonly  observed  in  intestinal  inflammation,  acute 
rheumatism,  intermittent  fever.  Donne  and  Frerichs  assert  that  acidity 
of  the  saliva  depends  on  an  irritation  of  the  buccal  mucous  membrane. 

The  specific  gravity  of  mixed  saliva  varies  from  1.004  to  1.009.  These 
variations  depend  on  many  different  causes,  there  being  a  diminution  after 
the  taking  of  drink,  and  a  greater  increase  after  taking  food,  than  even  is 
observed  in  the  fasting  state.  An  animal  diet  especially  increases  it. 

Under  ordinary  circumstances,  the  saliva  is  secreted  to  an  amount  of 
Quantity  of  from  15  to  20  ounces  daily.  The  exudation  is  more  copious 
saliva.  during  mastication,  speaking,  reading,  more  being  produced  by 
the  use  of  hard  than  soft  food.  Mental  emotions  exert  a  control  over  its 
flow,  sometimes  diminishing  it,  as  in  moments  of  anxiety,  sometimes  in- 
creasing it,  as  by  the  anticipation  of  food.  After  eating,  the  flow  contin- 
ues to  a  considerable  extent ;  it  is  also  provoked  by  the  use  of  aromatics. 
On  irritation  of  the  interior  of  the  stomach  through  a  gastric  fistula,  the 
flow  is  simultaneous  with  that  of  the  gastric  juice. 

The  movements  of  the  jaw  and  the  pressure  of  the  food  give  rise  to  va- 
riations in  the  quantity  of  saliva.  It  is  perhaps  for  these,  reasons  that  the 
parotid  gland  on  that  side  of  the  mouth  which  is  most  used  in  mastication 
secretes  more  than  the  other.  Of  the  proportion  of  the  different  kinds  of 


CONSTITUTION   OF   SALIVA.  45 

saliva  in  the  mixed  secretion,  nothing  is  known  with  certainty  in  the  case 
of  man,  but  it  is  said  that  in  horses  the  parotids  furnish  two  thirds,  the 
submaxillaries  one  twentieth,  and  the  sublinguals  and  mucous  follicles 
the  rest.  The  secretion  of  the  saliva  goes  on  during  sleep. 

To  the  active  organic  substance  of  the  saliva  the  designation  of  ptya- 
line  has  been  given.     It  is  regarded  as  a  ferment,  possessing  in 
several  respects  the  properties  of  diastase,  and  hence  has  been     t>a 
called  by  Mialhe  diastase  salivaire. 

For  the  purpose  of  analysis,  saliva  should  be  obtained  in  a  perfectly 
fresh  state,  a  condition  not  easily  fulfilled,  for  it  decomposes  or  changes 
with  rapidity. 

During  these  changes,  alkaline  carbonates,  for  example,  are  formed  in 
abundance,  though  they  may  have  existed  but  to  a  small  extent  at  first. 
We  have  already  seen  that  in  this  way  parotid  saliva,  ex-  Constitution  of 
posed  to  the  air,  yields  crystals  of  carbonate  of  lime.  The  saliva- 
following  table  is  presented  as  offering  an  example  of  the  average  consti- 
tution of  mixed  saliva. 

Constitution  of  the  Saliva  (Frerichs). 

Water 994.10 

Epithelium  and  mucus 2.13 

Fat 07 

Ptyaline  and  alcohol  extract 1.41 

Sulphocyanide  of  potassium 10 

Fixed  salts 2.19 

1000.00 

Of  the  fixed  salts  the  chief  are,  the  phosphates  of  soda,  lime,  and  mag- 
nesia, and  the  chlorides  of  sodium  and  potassium.  The  sulphocyanide 
of  potassium  varies  in  amount  considerably :  it  increases  after  meals,  and 
.especially  after  the  use  of  condiments,  salt,  pepper,  spices.  Those  arti- 
cles wiuch  contain  sulphur,  as  mustard,  garlic,  radishes,  increase  its  amount 
in  a  very  marked  manner. 

Not  only  does  the  saliva,  as  derived  from  the  different  glands,  present 
differences  of  constitution ;  it  likewise  differs  in  various  ani-  Modifications 
mals,  and  in  the  same  animal  according  to  its  age.  This  is  of  saliva- 
observed  even  in  the  case  of  man.  The  saliva  of  an  infant  at  the  breast 
possesses  very  little  power  of  saccharizing  starch,  a  transmutation  which 
that  of  the  adult  accomplishes  with  energy. 

The  action  of  this  secretion  appears  to  be  limited  to  starch,  and  certain 
kinds  of  sugar,  which  first  yield  lactic  and  then  butyric  acid.  It  does  not 
exert  any  influence  in  transforming  albuminous  matter. 

The  saliva  discharges  many  functions.     It  is  a  necessary  intermedium 
in  the  sense  of  taste,  for  substances  to  be  sapid  must  be  more  Functions  of 
or  less  soluble  in  this  juice.     If  insoluble,  they  are  tasteless.  SJfliva- 
It  also  moistens  the  interior  of  the  mouth,  and  prevents  the  sensation  of 


46  SALIVARY  DIGESTION   IN  THE   STOMACH. 

dryness.  But  its  chief  duty  seems  to  be  that  of  promoting  the  digestive 
operation ;  for,  though  the  food  remains  in  the  mouth  but  a  short  time, 
the  action  of  the  saliva  is  prolonged  after  the  masticated  mass  has  been 
deposited  in  the  stomach.  Though  the  direct  admixture  of  saliva  with 
gastric  juice  injures  the  power  of  the  latter,  this  effect  does  not  ensue  in 
the  stomach,  since  they  act  for  the  most  part  separately.  The  action  of 
the  gastric  juice  is  superficial,  and  two  distinct  operations  are  therefore 
conducted  at  the  same  moment,  the  surface  of  the  food  changing  under 
Action  of  the  the  influence  of  the'  gastric  juice}  and  the  inner  portion  under 
dnued^the  that  of  tlie  saliva'  l  Mieve  that  in  this  manner  the  salivary 
stomach.  juice  lends  itself  to  stomach  digestion,  for  it  is  well  known 
that  by  its  aid  starch  changes  into  grape  sugar,  and  the  transmutation 
does  not  stop  at  that  point,  but  goes  on  to  the  production  of  lactic  acid. 
An  acid  juice  is  essential  to  stomach  digestion. 

After  the  administration  of  balls  of  starch  to  animals  in  which  gastric 
Production  of  fistulas  have  been  established,  sugar  may  be  detected  in  the 
sugar  from  stomach  in  the  course  of  ten  or  fifteen  minutes.  It  does 
stomach  bythe  not  appear  that  there  is  any  relation  between  the  quantity 
saliva.  Of  saliva  incorporated  by  mastication  and  the  quantity  of 

starch  in  the  food.  Animals  which  swallow  their  food  without  mastica- 
tion have  either  no  parotids,  or  those  organs  exist  in  only  a  rudimentary 
state ;  commonly,  however,  their  submaxillary  glands  are  large.  Un- 
der the  most  favorable  circumstances,  the  digestion  of  starchy  food  is 
scarcely  ever  complete,  a  considerable  portion  being  found  in  the  excre- 
ment. The  true  function  of  the  saliva  has  been  well  illustrated  by  in- 
serting amylaceous  food  into  the  stomach  of  dogs  with  gastric  fistula?, 
after  tying  the  salivary  ducts,  in  which  case  no  sugar  can  be  detected. 

It  has  been  suggested  that  the  eventual  arrest  of  the  action  of  saliva 
on  reaching  the  stomach  may  be  due  to  the  digestion  of  its  ptyaline  by 
the  gastric  juice.  In  artificial  experiments,  however,  such  a  digestion 
or  destruction  can  not  be  accomplished. 

The  double  digestion,  partly  salivary  and  partly  gastric,  occurring  in 
the  stomach,  is  doubtless  one  of  the  causes  of  those  differences  which 
have  been  noticed  between  the  natural  action  of  that  organ  and  the  arti- 
ficial imitations  of  it.  The  influence  of  the  saliva,  even  under  these, 
which  may  seem  at  first  sight  to  be  unfavorable  circumstances,  is  far 
from  being  trivial,  an  effect  which  is  well  illustrated  by  the  instantane- 
ous manner  in  which  a  solution  of  starch  in  water,  mixed  with  an  equal 
quantity  of  saliva  and  agitated,  is  transmuted  into  a  solution  of  sugar. 
In  a  few  moments  its  viscidity  is  lost,  it  fails  to  give  the  blue  reaction 
with  iodine,  becomes  sweet  to  the  taste,  and  readily  answers  to  Trom- 
mer's  test. 
*  Besides  the  duties  which  have  been  mentioned,  the  saliva  incidentally 


RELATION   OF  THE   SALIVARY   GLANDS  AND   KIDNEYS.  47 

accomplishes  a  secondary  object  by  its  power  of  retaining  gasefe  in  its 
froth  or  foam.     Atmospheric  oxygen  by  this  means  is  incor-  Saliva  carries 
porated  with  the  food  during  mastication,  and  is  thus  enabled  air  into  the 
to  exert  an  important  influence  in  promoting  the  action  of 
the  •  gastric  juice.     For  to  the  inception  of  the  change  which  that  juice 
impresses  on  the  food,  oxygen  is  necessary.     It  is  brought  into  the  cav- 
ity of  the  stomach  entangled  or  dissolved  in  the  saliva. 

It  has  just  been  mentioned  that  the  action  of  saliva  on  starch  is  not  re- 
stricted to  the  production  of  sugar,  but  that  it  may  end  in  the  Lactic  acid 


formation  of  lactic  acid.     If,  therefore,  any  thing  intervenes  to 


check  the  supply  of  hydrochloric  acid,  which  usually  gives  drochioric. 
acidity  to  the  gastric  juice,  the  system  possesses  vathin  itself  the  means 
of  compensating  for  the  difficulty..  In  the  interior  of  the  digesting  mass 
lactic  acid  is  being  set  free.  This  acid,  as  has  long  been  known,  can  re- 
place hydrochloric  acid  in  its  physiological  duty. 

Though  so  large  a  quantity  of  saliva  as  20  ounces  may  be  secreted  in 
a  day,  this  being  about  one  half  of  the  urinary  discharge,  it  is  to  be  re- 
membered that  the  water  is  not  lost  to  the  system,  as  in  the  latter  case. 
When  the  impure  habit  of  profuse  spitting  is  indulged  in,  it  Disgusting  ef_ 
is  interesting  to  remark  the  reflected  effect  which  takes  place  feet  of  profuse 
in  the  reduced  quantity  of  the  urine,  and  an  instinctive  desire 
for  water,  a  kind  of  perpetual  thirst.  It  is  probable  that,  under  these  dis- 
gusting circumstances,  the  percentage  amount  of  saline  substances  in  the 
saliva  is  increased,  and  that,  so  far  as  that  class  of  bodies  is  concerned, 
the  salivary  glands  act  vicariously  for  the  kidneys,  and  the  mouth  is  thus 
partially  converted  into  a  urinary  aqueduct. 

The  relation  between  the  salivary  glands  and  the  kidneys  is  very  well 
shown  after  the  administration  of  such  substances  as  the  Relation  of  the 
iodide  of  potassium.  If  five  grains  of  this  salt  be  taken  in  and^hlkid"  S 
pills,  and  the  mouth  be  then  thoroughly  washed,  in  the  course  neys. 
of  a  quarter  of  an  hour  the  saliva  will  readily  strike  a  blue  tint  when 
tested  with  nitric  acid  and  starch,  but  the  urine  will  not  show  that  reac- 
tion until  after  a  considerable  interval,  perhaps  even  an  hour  or  more.  It 
w.ould  therefore  appear  that  such  a  salt  must  pass  again  and  again  through 
the  salivary  glands  before  it  is  finally  disposed  of  by  the  kidneys,  which 
oifer  the  only  outlet  for  its  total  removal. 

Among  the  functions  of  the  saliva  we  ought  not  to  overlook  the  influ- 
ence which  its  rapid  secretion  must  exert  on  the  state  of  tension  of  the 
blood-vessels,  an  influence  which  probably  favors  the  absorption  going  on 
in  the  stomach  and  intestines. 

Thus  prepared  by  mastication  and  in,salivation,  the  food  descends  into 
the  stomach,  passing  along  the  pharynx,  which  dilates  to  receive  it.  The 
rima  glottidis  spontaneously  closes,  and  additional  security  is  given  to  the 


48 


THE   DIGESTIVE   TEACT. 


tract. 


Fig.  3. 


respiratory  passage  by  the  valve-like  shutting  of  the  epiglottis.  Through 
the  oesophagus  the  morsel  advances  "by  the  contraction  of  the  muscular 
coat,  with  a  wave-like  or  undulating  motion  onward.  The  food  is  now  de- 
livered at  the  cardiac  orifice  of  the  stomach,  and,  entering  that  organ,  is  sub- 
mitted to  the  gastric  juice,  which  is  exuding  from  the  mucous  membrane. 
The  digestive  tract  may  be  considered  as  presenting  six  prominent  re- 
iiiustration  of  §^ons — ^e  moutn> tne  pharynx,  the  oesophagus,  the  stomach, 
the  digestive  the  small  intestine,  the  large  intestine.  Their  relative  posi- 
tion and  subdivisions  are  illustrated  in  Figure  3. — 1,  the 
tongue ;  2,  2,  the  pharynx ;  3,  3,  the 
oesophagus;  4,  the  velum  pendulum 
palati ;  5,  section  of  the  larynx ;  6,  the 
palate ;  7,  the  epiglottis ;  8,  the  thy- 
roid cartilage;  9,  the  medulla  spina- 
lis;  10,  10,  bodies  of  vertebra3;  11, 
12,  spinous  processes  of  ditto ;  13, 
cardiac  orifice  of  stomach ;  14,  splenic 
extremity;  15,  pyloric  extremity;  16, 
16,  greater  curvature;  17,  the  less 
curvature ;  18,  pylorus ;  19,  superior 
transverse  portion  of  duodenum ;  20, 
middle  or  perpendicular  portion  ;  21, 
inferior  transverse  portion ;  22,  gall- 
bladder ;  23,  cystic  duct ;  24,  hepatic 
duct;  25,  ductus  communis  choledo- 
chus;  26,  its  aperture  in  the  duode- 
num ;  27,  duct  of  the  pancreas,  empty- 
ing into  the  duodenum  near  to  the  place 
of  entry  of  the  ductus  communis  chole- 
dochus ;  28,  commencement  of  jeju-  . 
num ;  29,  29,  29,  jejunum ;  30,  30, 30, 
ileum;  31,  ileum  opening  into  great 
intestine ;  32,  ileo-colic  valve ;  33,  il- 
eo-ccecal  valve;  34,  ccecum;  35,  ap- 
pendix vermiformis ;  36,  36,  the  as- 
cending colon ;  37,  transverse  arch  of 
colon ;  38,  descending  colon ;  39,  sig- 
moid  flexure ;  40,  rectum  ;  41,  anus. 

From  the  interior  or  mucous  coat  of 
the  stomach  the  gastric  juice  exudes. 
This  fluid  may  be  best  obtained  for  ex- 
amination by  gastric  fistulas  artificially 
The  hUman  digestive  tract.  established  in  animals.   As  respects  the 


THE   GASTRIC  JUICE.  49 

aspect  of  the  interior  of  the  stomach,  Dr.  Beaumont,  who  had  an  opportuni- 
ty of  examining  it  in  the  case  of  Alexis  St.  Martin,  describes  Aspect  of  inte- 
it  as  of  a  light  pink  color,  its  velvety  surface  Ibeing  coated  nor  of  stomach. 
over  with  mucus.  On  the  introduction  of  food  or  any  irritant,  lucid 
points  protrude  from  the  mucous  coat ;  these  are  the  mouths  of  the  folli- 
cles from  which  the  juice  exudes.  When  in  activity,  the  temperature 
of  the  interior  of  the  organ  is  about  100°  Fahr. 

The  gastric  juice  is  a  viscid  fluid,  with  an  acid  reaction  and  faint  odor. 
After  filtration  through  paper  it  is  clear  and  transparent,  and  The  gastric 
possesses  all  its  physiological  qualities.  The  impurities  thus  Juice- 
separated  from  it  are  merely  old  undigested  residues,  on  which,  in  no  re- 
spect, its  qualities  depend.  It  does  not  become  turbid  at  212°,  remains 
long  undecomposed,  and  retains  its  digestive  power  even  after  it  has  be- 
come mouldy.  It  does  not  accumulate  in  the  stomach  while  fasting,  but 
requires  a  stimulus  for  its  ejection,  and  even  then  is  produced  in  a  limit- 
ed quantity  only.  It  is  secreted  by  the  follicles  of  the  mucous  membrane 
of  the  stomach,  which  follicles  may  be  described  as  cup-shaped  cavities, 
about  the  two  hundredth  of  an  inch  in  diameter,  from  the  bottom  of  which 
project  two  or  more  parallel  tubes,  the  mouth  of  the  cup  open-  itissecretedby 
ing  into  the  stomach,  and  the  tubes  ending  in  a  closed  term-  follicles, 
ination  in  the  tissue  beneath.  Toward  the  pylorus  the  cups  become  deep- 
er, so  as  to  assume  the  form  of  a  cylinder,  and  the  projecting  tubes  are 
shorter.  Between  these  follicles  blood-vessels  pass.  They  are  ramifica- 
tions from  the  cceliac  axis,  and  discharge  a  double  function.  As  the  ar- 
terial branches  invest  the  roots  of  the  tubes,  they  furnish  nutrition  for  the 
cells  which  are  produced  in  crowds  at  that  part  of  the  arrangement ;  but 
when  they  have  gained  the  interior  of  the  mucous  membrane,  and  are  in 
the  ridges  between  the  follicles,  having  assumed  the  character  of  veins, 
they  act  as  absorbents,  conducting  the  material  which  is  sufficiently  di- 
gested into  the  portal  circulation.  Agreeably  to  this,  these  vessels  have 
a  larger  diameter  than  capillaries  generally.  It  seems,  therefore,  that  the 
function  of  the  tube  is  the  production  of  cells,  which,  originating  from 
germs  at  the  bottom  and  sides  of  each  tube,  become  perfected  as  they  pass 
forward,  and  soon  after  their  extension  burst  or  deliquesce,  and  as  the 
material  they  discharge  does  not  possess  the  acid  reaction,  it  is  probably 
the  pepsin  element  of  the  gastric  juice. 

Constitution  of  the  Gastric  Juice  of  the  Dog. 


Gastric  j  uice, 
without  saliva. 

Gastric  juice, 
with  saliva. 

Water  . 

973  062 

971  171 

Pepsin  

17.127 

17336 

Hydrochloric  acid  

3  050 

2  337 

Chlorides  of  pot.,  sod.,  calc.,  amm  
Phosphates  of  lime,  magn.,  iron  

4.724 
2.037 

6.418 
2.738 

1000.000 

1000.000 

D 


50 


STOMACH   FOLLICLES. 


The  preceding  table,  from  Hublbenet,  shows  that  nearly  two  thirds  of 
Pro  erties  of  ^ie  s0^  matcr^  °^  ^e  gastric  juice  is  pepsin.     Exposure 


the  gastric 
juice. 


to  a  very  low  temperature  does  not  deteriorate  the  properties 
of  this  substance,  for  it  will  resume  its  activity  even  after  be- 
ing frozen.  But,  on  the  contrary,  a  temperature  approaching  ebullition 
destroys  its  solvent  power,  and  the  same  effect  ensues  when  it  is  neutral- 
ized by  an  alkali. 

The  gastric  juice  acts  on  iron  or  zinc  with  evolution  of  hydrogen,  an 
effect  which  the  acid  phosphate  of  lime  can  not  produce.  This  seems 
to  be  decisive  against  the  views  of  those  physiologists  who  have  imputed 
its  reaction  to  the  latter  substance. 

The  digestive  power  of  this  juice  is  impeded  by  the  presence  of  almost 
any  alkaline  salt.     To  this  remark  common  salt  offers  no  exception.     It 
is  owing  to  its  alkalinity  that  saliva  injures  the  digesting  power  of  gas- 
tric juice.     On  the  contrary,  that  power  is  very  much  increased  by  the 
Fig.  4  presence  of  fat,  which  promotes  the  conversion 

of  protein  bodies  into  peptones. 

The  mucous  membrane  of  the  stomach  pre- 
sents a  reticulated  appearance,  as  shown  in  Fig. 
Stomach  foiii-  4.  At  the  bottom  of  each  compart- 


Mucous  membrane  of  the  stomach 
magnified  TO  diameters. 


and  functions'     foUideS,  the  size  and  depth  of  wllidl 

increase  toward  the  pylorus.  Their  exterior  is 
partly  covered  with  columnar  epithelium,  which  extends  over  the  inter- 
vening  ridges  ;  the  residue  is  glandular,  and  continu- 
ally gives  origin  to  granules.  The  upper  part  of 
each  follicle,  as  well  as  the  entire  surface  of  the  mu- 
cous membrane,  is  usually  covered  with  mucus. 

In  Fig.  5  is  a  representation,  given  by  Todd  and 
Bowman,  of  stomach  follicles  and  their  tubes  in  a 
vertical  section.  The  specimen  is  from  the  dog  after 
twelve  hours  fasting.  A  represents  these  structures 
in  the  middle  region  of  the  stomach  ;  B  in  the  pylor- 
ic  region  ;  a  a,  orifices  of  the  follicles  on  the  inner 
surface*  of  the  stomach  ;  b  b,  different  depths  at  which 
the  columnar  epithelium  is  exchanged  for  glandular  ; 
d,  pyloric  tubes  terminating  variously,  and  lined  to 
their  extremities  with  columnar  epithelium. 

Fig.  6,  A,  horizontal  section  of  a  stomach  folli- 
cle a  little  way  within  its  orifice  ;  <z,  basement  mem- 
brane ;  by  columnar  epithelium.  All  but  the  centre 
of  the  cavity  of  the  cell  is  occupied  by  a  transparent  mucus,  which  seems 
to  have  oozed  from  the  open  extremities  of  the  epithelial  particles  ;  c, 


Vertical  section  of  stomach 
follicles  and  tubes  magni- 
fied 150  diameters. 


HYDROID  STRUCTURE   OF  THE   STOMACH. 


51 


Fig.  6. 


fibrous  matrix  surrounding  and  supporting  the  basement  membrane ;  d, 
small  blood-vessels. 

B,  horizontal  section  of  a  set  of  stomach  tubes 
proceeding  from  a  single  cell.  The  letters  refer 
to  corresponding  parts.  The  epithelium  is  glan- 
dular, the  nuclei  very  delicate,  and  the  cavity  of 
-the  tubes  very  small,  and  in  some  cases  not  visi- 
ble. (From  the  dog,  by  Todd  and  Bowman,  after 
twelve  hours'  fasting.) 

It  thus  appears  that  there  are  at  least  two  dis- 
tinct classes  of  stomach  follicles,  differ-  Varieties  of 
ing  from  each  other  in  anatomical  con-  stomach  foi- 
struction,  and,  as  there  is  now  reason  to  ] 
believe,  also  in  physiological  function,  those  which 
are  near  the  pylorus  yielding  a  secretion  which, 
taken  by  itself,  exerts  only  a  tardy  action  in  pro- 
ducing the  solution  of  protein  bodies,  but  those 
from  the  middle  and  other  portions  of  the  organ 

Horizontal  section  of  stomach  fol-  T   i  •          ,1  i     ,  •  ,1  T,    • 

licles  and  tubes  magnified  200  di-    accomplishing  that  Solution  promptly.       It  IS  SUS- 

pected  that  the  acid  of  the  gastric  juice  is  yielded 
by  one  class  of  these  structures,  and  the 
pepsin  by  the  other. 

A  general  idea  of  the  structure  of  these 
secreting  follicles  may  perhaps  be  obtained 
by  likening  each  of  them  to  a  little  glove, 
the  hand  of  which  opens  into  the  stomach, 
and  the  fingers  project  upon  the  submucous 
tissue  beneath.  From  the  sides  and  tip  of 
each  finger,  cells  may  be  supposed  to  arise 
continually,  and,  as  they  are  crowded  for- 
ward, they  undergo  development,  leaving 
the  hand  in  a  perfect  condition,  and  deli- 
quescing as  they  pass  into  the  stomach. 

Though  we  have  spoken  of  these  folli- 
cles as  excavations  or  cup-like  depressions 
in  the  mucous  tissue,  according  to  the  de- 
scription usually  given  of  them  Hydroidcon. 
by  anatomists,  it  is  to  be  under-  struction  of 
stood  that  this  view  of  their  con-  t] 
struction   is   philosophically  incorrect,  for 
each,  instead  of  being  a  mere  excavation,  is 
truly  a  distinct  organism,  analogous  in  struc- 
The  hydra.  ture  and  many  of  its  functions  to  a  polype. 


52  QUANTITY   OF   GASTRIC   JUICE. 

The  hydra,  a  fresh-water  polype,  may  be  taken  as  the  type  of  this  organ- 
ism. This  animal,  Fig.  7,  consists  of  a  bag  or  digestive  sac,  a  a,  end- 
ing in  a  cylinder,  #,  the  opening  to  which  is  furnished  with  numerous 
tentacles,  c  c  c  ;  the  tentacles  enfold  in  their  grasp  objects  on  which  the 
hydra  feeds,  and  by  their  contractions  carry  them  to  the  sac.  Into  the 
interior  of  the  sac  a  juice  exudes  possessing  digestive  powers,  and  soon 
dissolving  food. 

We  may  therefore  regard  the  follicular  structure  of  the  stomach  as  a 
colony  of  polypes,  the  tentacles  of  which  are  converged  into  a  muscular 
tube,  constituting  the  oesophagus.  In  a  stomach  of  ordinary  size  there 
are  probably  a  million  of  these  organisms.  Digestion  is  undoubtedly 
conducted  on  the  same  physical  principles  in  both  cases,  though  in  the 
polype  the  food  matter  enters  the  follicular  cavity  of  which  the  body  of 
the  animal  consists,  but  in  man  is  contained  in  the  stomach,  into  which 
the  follicles  open,  and  pour  forth  their  digestive  fluid. 

With  respect  to  the  acid  constituent  of  the  gastric  juice,  it  appears  to 
be  hydrochloric  or  lactic.  The  latter  has  probably  originated  in  the  man- 
ner just  described  by  the  action  of  the  saliva  on  amylaceous  bodies ;  the 
former  undoubtedly  comes  from  the  common  salt  ingested.  Perhaps,  un- 
der a  deficiency  of  common  salt,  lactic  acid  discharges  the  entire  duty. 
Schmidt  regards  the  digestive  principle  as  a  conjugated  acid,  the  nega- 
tive constituent  being  hydrochloric  acid,  and  pepsin  being  the  adjunct, 
the  compound  being  analogous  to  ligno-sulphuric  acid.  About  twenty 
Quantity  of  parts  of  gastric  juice  are  required  to  digest  one  part  of  dry  al- 
gastric  juice.  ]oumen,  and  about  70  ounces  are  secreted  in  a  day.  If  the 
hourly  destruction  of  fibrin  in  average  muscular  action  is  62  grains,  about 
60  ounces  of  gastric  juice  would  be  required  each  day  for  muscular  repair. 
A  very  large  demand  is  therefore  made  upon  the  water  in  the  system  for 
this  use.  But  here  the  same  remark  is  to  be  made  as  in  the  case  of  the 
saliva ;  the  water,  after  accomplishing  its  object,  is  not  lost  to  the  econ- 
omy, but  is  immediately  reabsorbed. 

It  was  remarked,  in  speaking  of  the  salivary  glands,  that  their  secre- 
Re  eated  as  **on  Passes  repeatedly  through  them,  the  saliva,  as  it  exudes, 
sage  of  extra-  being  swallowed,  reabsorbed,  and  so  secreted  over  and  over 
through0  the  agam'  ^n  these  repeated  passages,  many  salt  substances, 
stomach  foiii-  such  as  the  iodide  and  bromide  of  potassium,  will  accompany 
it,  the  kidneys,  however,  eventually  removing  such  extraneous 
bodies.  In  like  manner,  heterogeneous  matters  will  make  a  repeated  cir- 
culation through  the  gastric  follicles  before  a  final  removal  by  the  kid- 
neys. When  the  latter  organs  have  been  extirpated,  the  constituents  of 
their  secretion,  such  as  urea,  may  appear  in  the  stomach. 

On  the  deposit  of  the  food  in  the  stomach,  a  movement  of  translation 
is  given  to  it  by  the  alternate  contraction  and  relaxation  of  the  fibres  of 


SUMMARY  OF   STOMACH   DIGESTION.  53 

the  muscular  coat,  aided  to  a  considerable  extent  by  the  respiratory 
movements  of  the  abdominal  walls.     The  course  of  this  ro-  Motions  of  *the 
tation  commonly  is,  that  after  passing  the  cardiac  orifice  the  food  in  the 
food  moves  from  right  to  left  round  the  great  extremity,  and  S1 
then  along  the  large  curvature  from  left  to  right,  returning  along  the  small 
curvature,  and  occupying  from  one  to  three  minutes  to  perform  this  revo- 
lution, the  motion  continuing  for  a  few  minutes  at  a  time. 

While  this  is  going  forward  digestion  is  rapidly  taking  place,  and  the 
portions  which  have  suffered  complete  action  are  oozing  through  the  py- 
loric  valve  into  the  intestine  as  a  semi-fluid  and  apparently  Formation  of 
homogeneous  material  called  chyme.  This  process  has  fairly  chvme- 
set  in  in  the  course  of  an  hour,  and  is  usually  finished  in  about  four. 
In  consistency,  color,  and  chemical  reaction,  the  chyme  varies  with  the 
nature  of  the  food,  its  chemical  constitution,  and  its  quantity ;  but  under 
common  circumstances  it  presents  the  acid  reaction,  for  it  is  to  be  remem- 
bered that  the  diurnal  supply  of  hydrochloric  acid  to  the  stomach  is  about 
the  fifth  of  an  ounce.  Arrived  in  the  intestine,  the  chyme  is  pushed  for- 
ward by  the  peristaltic  movements,  and  soon  after  its  appearance  in  the 
duodenum  is  mixed  with  several  important  fluids — the  bile,  which  is  fur- 
nished by  the  liver,  the  secretion  of  the  pancreas,  and  the  enteric  juice 
which  is  exuding  from  Brunner's  glands. 

The  digestion  of  the  albuminous  part  of  the  food  commences  in  the 
stomach,  and  in  that  cavity  advances  far  toward  completion.  Summary  of 
The  action  is  not  merely  for  the  purpose  of  bringing  those  dige™^n1n 
substances  into  a  state  of  solution  in  water,  but  also  of  modi-  the  stomach, 
fying  them  chemically.  This  change  is  so  well  marked  that  it  has  been 
found  expedient  to  indicate  it  by  a  designation,  and  hence  we  speak  of 
albumen  peptone,  fibrin*  peptone,  casein  peptone.  These  peptones  are, 
for  the  most  part,  absorbed  by  the  blood  capillaries,  though  a  portion  of 
them  enters  the  circulation  as  a  constituent  of  chyle.  In  the  system, 
whatever  their  origin  may  have  been,  they  seem  to  revert  to  the  state  of 
blood  albumen.  But,  though  the  production  of  these  peptones  is  accom- 
plished to  the  extent  that  has  been  mentioned  in  the  stomach  by  the  gas- 
tric juice,  the  action  is  continued  and  brought  to  its  completion  in  the 
small  intestine  by  the  aid  of  the  intestinal  juice.  It  does  not  appear  that 
the  large  intestine  participates  in  this  duty,  since  portions  of  coagulated 
albumen,  or  of  flesh  introduced  into  it  through  fistulous  openings,  are 
voided  through  the  rectum. 

Such  is  the  general  description  of  the  act  of  digestion.     We  have  next 
to  enter  on  a  physical  examination  of  what  it  is  that  really  Influence  Of 
takes  place  in  the  stomach.     It  was  formerly  supposed  that  the  nerves  on 

d,.     i      j        ,  .  .(.  ,,  digestion, 

igestion  is  entirely  due  to  nervous  agency,  since,  if  the  prieu- 

mogastric  nerves  be  divided,  the  process  is  very  much  interfered  with. 


54  ARTIFICIAL  DIGESTION. 

But  this  interference  takes  place  only  in  an  indirect  way,  for  the  section 
of*  those  nerves  is  attended  with  such  a  paralysis  of  the  stomach  that 
those  movements  which  so  well  serve  to  mix  up  the  food  with  the  gas- 
tric juice,  and  expel  it  through  the  pyloric  valve,  are  put  an  end  to. 

Bidder  and  Schmidt,  from  an  examination  of  four  dogs  with  gastric 
Effect  of  section  fistnlge,  demonstrated  that  the  section  of  the  pneumogastric 
of  the  pneumo-  nerves  does  not  exert  that  influence  on  the  secretion  of  the 
gastric  juice  which  had  been  formerly  supposed,  for  both  in 
quantity  and  composition  it  remained  the  same.  Even  in  those  cases  in 
which  both  they  and  others  have  observed  a  diminution  in  its  amount, 
the  result  ought,  probably,  to  be  referred  to  the  shock  given  to  the  entire 
system  by  the  severity  of  the  operation. 

The  acidulating  material  of  the  gastric  juice  is  hydrochloric  acid.  Is 
it  possible  by  artificial  mixtures  containing  that  substance  to  reduce 
food  articles  to  a  digested  condition  ?  This  inquiry  introduces  a  descrip- 
tion of  the  experimental  investigations  which  have  been  made  in  artificial 
digestion. 

When  water  acidulated  with  hydrochloric  acid  is  kept  in  contact  with 
Artificial  di-  albumen,  no  action  is  perceptible  at  ordinary  temperatures  in  a 
gestion.  moderate  period  of  time.  If  the  temperature  is  raised  to  about 
150°  a  slow  dissolution  ensues,  which  becomes  better  marked  as  the  heat 
rises  toward  212°. 

f  But  if  to  the  weak  hydrochloric  acid  thus  made  to  act  on  albumen, 
pepsin  is  added,  the  solution  takes  place  with  rapidity  at  moderate  tem- 
peratures. An  ounce  of  water,  mixed  with  twelve  drops  of  hydrochloric 
acid  to  which  one  grain  of  pepsin  has  been  added,  will  completely  dis- 
solve the  white  of  an  egg  in  two  hours  at  a  temperature  of  100°.  It 
acts  in  the  same  manner  on  cheese  or  flesh,  these  nitrogenized  articles 
being  converted  into  soluble  non-coagulable  bodies.  The  acid  does  not 
enter  into  chemical  combination  with  the  dissolving  organic  matter.  It 
may  be  recovered  from  the  solution  by  resorting  to  proper  processes. 

When  striated  muscular  tissue  is  submitted  to  artificial  digestion,  it  is 
Artificial  di-  ^rst  divided  into  its  constituent  fasciculi,  and  the  transverse 
gestion  of  mus-  stride  then  disappear,  the  sarcolemma  being  destroyed.  The 
course  of  the  action  seems  to  be  the  same  in  natural  diges- 
tion. In  the  fcecal  matter,  shreds  of  muscular  fasciculi  still  bearing  their 
striation  may  be  discerned.  These,  having  by  chance  escaped  solution 
during  their  sojourn  in  the  stomach,  have  passed  through  the  whole 
length  of  the  digestive  tube  unchanged. 

Pepsin — the  substance  resorted  to  in  these  experiments — may  be  ob- 
tained by  macerating  the  mucous  membrane  of  the  stomach 

Pepsin,  prep-  •'  &  1-1 

aration  and  for  a  short  time  in  lukewarm  water.  This  water,  along  with 
properties  of.  a  ^^  Of  tne  pepsin,  removes  various  impurities  ;  it  may  there- 


FUNCTIONS   OF  PEPSIN.  55 

fore  be  cast  away  $  the  maceration  being  then  continued  with  a  fresh  por- 
tion of  cold  water,  and  this  being  submitted  to  nitration,  and  subsequent- 
ly evaporated  at  a  low  temperature  to  dry  ness,  yields  the  pepsin  as  a 
gummy  mass.  From  its  solutions  pepsin  may  be  precipitated  by  corro- 
sive sublimate  or  acetate  of  lead,  and  it  may  be  separated  from  those 
combinations  by  sulphureted  hydrogen.  Wasmann  availed  himself  of 
this  fact  to  obtain  it  in  a  pure  state. 

Composition  of  Pepsin.     (From  Schmidt.*) 

Carbon 530.00 

Hydrogen 67.00 

Nitrogen 178.00 

Oxygen 225.00 

1000.00 

From  this  it  would  appear  that  it  contains  less  carbon  and  more  nitro- 
gen than  the  members  of  the  protein  group. 

A  weak  acid  therefore  possesses  at  a  high  temperature  the  power  of 

bringing  into  a  state  of  solution  the  various  nitrogenized  food  _ 

-II  -.  o  -1       <>   i  -•  Pepsm  re- 

matters,  and  at  lower  degrees  fails  of  that  property ;  but  in  places  a  high 

the  presence  of  pepsin  the  solvent  powers  are  assumed  un-  temPerature. 
der  the  latter  circumstances,  and  therefore  it  is  said  of  this  substance 
that  it  replaces  a  high  temperature.  By  its  aid,  hydrochloric  or  lactic 
acids  present  in  the  stomach  reduce  the  food  to  a  uniform  pulpy  mass 
— the  chyme.  Of  all  acids,  these,  however,  alone  arc  capable  of  forming 
digestive  fluids. 

Formerly  it  was  supposed  that  the  act  of  digestion  was  simply  me- 
chanical, the  food  being  ground  down  to  chyme  by  the  mo-  R  »  ex 
tions  of  the  stomach.  Reaumur's  experiments  showed  the  perimcntswith 
error  of  this  supposition.  He  took  small  hollow  silver  balls,  Sllver  balls* 
perforated  with  holes,  and,  having  filled  them  with  meat,  caused  them  to 
be  swallowed  by  a  dog.  When  they  had  remained  in  the  animal's  stom- 
ach a  suitable  length  of  time,  they  were  withdrawn  by  a  thread  which 
had  been  previously  attached  to  them.  Now  if  the  stomach  acted  by  a 
triturating  or  grinding  power,  the  material  within  the  ball  would  be  en- 
tirely protected,  but  if  by  a  solvent  power  exerted  by  the  gastric  juice, 
the  digestion  should  at  most  be  only  delayed.  Accordingly,  it  was  found 
that  this  was  what  actually  took  place,  digestion  being  fully,  though  more 
slowly  accomplished,  the  action  commencing  on  the  outside  of  the  mate- 
rial, and  gradually  reaching  its  centre.  If  the  balls  were  kept  in  the 
stomach  long  enough,  they  came  out  quite  empty  at  last. 

The  idea  that  there  is  something  more  than  a  simple  solution  of  the 
food  effected  in  the  stomach,  that  some  mysterious  change  is  Chief  object  of 
impressed  upon  it  by  the  vitality  of  that  organ,  may  there-  tSrthe^oiu" 
fore  be  abandoned.  It  does  not  appear  that  there  is  any  es-  tionofthefood. 


56  NUTEITIVE  MATTER  IS   DISSOLVED. 

sential  difference  between  natural  digestion  and  the  artificial  imitation  of 
it,  either  as  respects  the  order  of  action  or  the  final  result.  Moreover, 
the  anatomical  consideration  that  the  food  is  yet  outside  the  body,  though 
it  is  inside  the  stomach,  should  be  sufficient  to  remove  all  errors  of  that 
kind.  A  living  surface,  such  as  the  skin,  never  exerts  any  chemical  ac- 
tion at  a  distance ;  and  the  lining  membrane  of  the  stomach,  both  as  re- 
gards its  physiological  origin  and  its  anatomical  relation,  is  nothing  more 
than  a  reflected  continuation  of  the  skin.  The  act  of  digestion  is  com- 
pleted long  before  the  nutrient  material  is  taken  up  by  the  lacteals  and 
veins,  and  thrown  into  the  torrent  of  the  circulation.  But  then,  and  not 
till  then,  is  the  food  fairly  in  the  interior  of  the  body. 

The  lacteals  and  veins  can  not  exert  their  absorbent  action  on  a  sub- 
stance presented  to  them  unless  it  is  dissolved  in  water.  If  not  abso- 
lutely dissolved,  at  least  it  must  be  in  that  condition  of  minute  subdivis- 
ion which  we  see  in  emulsions.  Though  it  has  been  stated  that  insolu- 
ble substances,  such  as  charcoal,  can  find  their  way  into  the  circulation 
in  the  solid  state,  there  does  not  appear  to  be  a  sufficient  weight  of  evi- 
dence to  support  such  an  improbability.  In  the  economy  of  plants,  it  is 
In  plants,  all  a  general  rule  that  nothing  can  have  access  to  the  interior  of 
nutrient  mate-  t}ieir  system  except  it  be  dissolved  in  water.  All  the  vari- 

rial  must  be  in  ITT  i  •  • 

solution  in  \va-  ous  gases  and  saline  substances  they  require  are  obtained  in 
ter-  a  state  of  solution ;  the  former  are  introduced,  for  the  most 

part,  through  the  leaves,  the  latter  through  the  roots.  The  object  aimed 
at  in  the  construction  of  the  digestive  apparatus  of  the  animal  mechanism 
is  absolutely  the  same.  Plants  use  as  their  food  inorganic  matter  only ; 
the  chief  materials  on  which  they  depend,  such  as  the  salts  of  ammonia 
and  carbonic  acid,  are  abundantly  soluble  in  water.  The  ascending  sap 
obtains  the  former  from  decaying  organic  residues  in  the  ground ;  the  at- 
mosphere presents  the  latter  unceasingly  to  the  leaves ;  and  since  the 
economy  of  many  plants  requires  earthy  salts,  as  silicates  and  phos- 
phates, which  are  of  sparing  solubility  in  water,  the  difficulty  arising  from 
that  want  of  solubility  is  avoided  by  the  introduction  of  an  immense  quan- 
tity of  water,  which,  after  bringing  into  the  plant  the  needful  amount  of 
mineral  material,  is  evaporated  off  at  the  leaves.  But  the  food  of  animals 
is  essentially  organic,  and  this,  before  it  can  be  received  into  their  blood, 
must  be  brought  into  the  dissolved  state.  It  must  be  submitted  to  a  pre- 
paratory operation  or  series  of  operations.  However  complicated  these 
The  operations  or  the  niechanism  which  accomplishes  them  may  be,  the  end 
on  the  food  are  aimed  at  is  clear.  The  action  begins  by  the  cutting,  tearing, 

purely  chemic-         ,  11-11         i     j 

aland  median-  and  crushing  movements  of  the  teeth,  which  break  down  all 
ical>  the  larger  portions,  and  carry  on  the  process  as  far  as  it  is 

possible  by  mechanical  means.  The  stomach  then  continues  the  subdi- 
vision by  chemical  agency,  to  the  end  that  a  condition  of  solution  may  be 


OBJECTS   OF  DIGESTION.  57 

attained.  Digestion  is  not,  therefore,  to  vitalize  the  food,  as  the  ancients 
supposed,  nor  to  communicate  to  it  any  new  or  obscure  properties ;  it  is 
for  the  purpose  of  comminuting,  subdividing,  dissolving,  or  bringing  it 
into  that  minutely  suspended  state  that  it  can  without  difficulty  submit 
to  the  absorbing  action  of  the  lacteals  and  veins.  There  is  a  complete 
analogy  between  this  operation  and  the  artificial  processes  to  which  the 
chemist  resorts  in  his  laboratory  for  the  solution  of  various  bodies.  He, 
too,  uses  mechanical  implements — the  mortar  and  pestle  to  grind,  the  ham- 
mer to  crush,  the  rasp  to  abrade.  When  these  have  carried  the  subdi- 
vision sufficiently  far,  he  resorts  to  acids  or  other  solvents,  and  thus 
breaks  down  the  compactness  of  the  hardest  minerals,  and  brings  them 
into  the  dissolved  state.  The  animal  world  presents  us  with  a  thousand 
illustrations  of  the  principles  here  set  forth,  mechanical  contrivances  curi- 
ously arranged.  For  instance,  birds,  whose  plan  of  organization  is  such 
as  to  meet  the  case  of  locomotion  through  the  air,  could  not  have  the  an- 
terior part  of  their  bodies  loaded  with  teeth,  accompanied  as  they  must 
have  been  with  a  powerful  muscular  apparatus.  Such  a  mechanism 
would  have  rendered  the  animal  top-heavy,  and  would  have  been  totally 
inconsistent  with  flying.  But,  to  avoid  this  difficulty,  that  which  might 
truly  be  regarded  as  the  mouth  is  lodged  in  the  interior  of  the  body,  nearer 
the  centre  of  gravity.  It  is  the  gizzard.  Instinct  teaches  the  bird  to 
swallow  small  angular  stones,  and  the  food,  rasped  between  powerful  mus- 
cular surfaces,  is  soon  brought  into  a  fit  condition  for  the  action  of  the 
stomach.  The  chemist,  too,  puts  fragments  of  glass  or  of  quartz  into  the 

mortar  in  which  he  is  conducting  the  reduction  of  a  tough  or  resisting 

o  o  o 

substance. 

The  first  object  of  digestion  is,  therefore,  the  subdivision  of  the  food. 
The  operation  begins  in  the  mouth  by  a  resort  to  mechanical  implements, 
and  when  these  have  carried  the  process  as  far  as  they  can,  the  stomach 
continues  the  duty.  In  its  cavity,  when  in  full  activity,  the  temperature 
is  100°  ;  a  periodically  increasing  and  relaxing  motion  of  revolution  is 
kept  up,  gastric  juice  exudes  in  definite  quantity,  the  hydrochloric  and 
lactic  acids  exert  their  action,  and  in  the  course  of  three  or  four  hours 
a  complete  reduction  is  accomplished. 

Allusion  has  been  made  to  the  probability  that  different  portions  of 
the  mucous  membrane  of  the  stomaeh  discharge  functions  Regional  divis- 
which  are  wholly  distinct,  one  portion  being  devoted  to  the  ^iSaSS^' 
elaboration  of  pepsin,  another  to  the  secretion  of  hydrochlo-  ent  functions. 
ric  acid,  another  to  the  preparation  of  a  special  mucus.  This  view  de- 
rives considerable  support  from  many  facts  in  comparative  physiology. 
In  those  cases  in  which  the  food  approaches,  in  its  mechanical  and  chem- 
ical condition,  to  the  form  which  it  is  destined  to  assume  as  a  part  of  the 
body  of  the  animal  receiving  it,  the  stomach  is  simple  in  construction, 


58 


DIGESTION  IN  INSECTS  AND  BIRDS. 


Fig.  8. 


and  is  little  more  than  a  mere  dilatation  of  the  alimentary  canal.     But 
Analogous  ar-    when,  as  among  the  herbivora  and  granivora, 
SffS*ni?     there  is  a  great  difference  Between  the  form 
mais.  of  the  food  received  and  the  form  of  the  tis- 

sues to  be  made,  the  digestive  sac  no  longer  presents 
such  a  simple  structure,  but  is  parted  off  into  distinct 
regions,  or  is  actually  converted  into  distinct  organs. 
Thus,  in  the  insect  digestive  tract  shown  in  Fig.  8, 

Digestives-  a  is  the  Phal7nx>  *  the  oesophagus,  lead- 
partmcnts  of  ing  into  a  crop  or  insalivatory  pouch,  c,  and 
this  into  the  gizzard,  d,  the  function  of  which 
is  to  rasp  up  and  abrade  the  more  resisting  portions  of 
the  food,  which,  when  this  is  accomplished,  passes  into 
the  true  stomach,  e,  and  from  thence  into  the  intestine,  g. 
The  delicate  vessels  about  f  are  supposed  to  be  biliary 
tubes,  and  h  glandular  secreting  organs. 

T-,  ,  f  •          i  Digestive  tract  of  a  car- 

Even  in  these  cases  of  minute  organization,  the  mu-       nivorous  beetle. 

cous  structure  remains  the  same  as  in  larger  animals  of  the  same  mode 

of  life.  The  photographic  represetita- 
tion  in  Fig.  9  displays  the  same  retic- 
ulated appearance  in  the  stomach  of 
the  carnivorous  beetle  as  has  been  de- 
scribed in  the  case  of  that  of  man; 
and  undoubtedly,  with  similarity  of 
structure  there  is  similarity  in  the  man- 
ner of  action. 

A  regional  division  of 
the  digestive  apparatus 
is  also  presented  in  the 
case  of  many  birds,  as 
is  shown  in  the  photo- 
graphic representation, 

Fig.  10,  in  which  we  have  the  digestive  tract  of  the  corn- 
Digestive  com-  mon  fow1'  a  be?inS  the  oesophag*8  leading 
into  the  insalivating  pouch  or  crop, 

which   empties  into  the  stomach,  c, 
and  this  into  the  gizzard,  d.      In  the  stomach, 
which  is  relatively  small,  the  digesting  material 
is  mingled  with  the  gastric  juice  before  being 
submitted  to  the  action  of  the  gizzard.     From 
the  gizzard  it  is  passed  into  the  small  intestine 
y,  f.     In  the  figure,  e  is  the  liver,  # ,  g,  the  cceca, 
and  h  the  cloaca.  Dlgcstive  tract  of  th:  common  fowl 


Fig.  10. 


Mucousmembraoeachofacarnivo- 


partments  of 


EEGIONAL  SUBDIVISIONS   OF  THE  STOMACH. 


59 


In  the  ostrich,  as  shown  \nFig.  11,  the  local  distribution  of  the  glan- 
Fid-  n-  _  duke  very  obviously  marks  out  a  regional  dis- 

tribution of  function.  C  is  the  cardiac  cav- 
ity, the  mucous  membrane  of  which  is  stud- 
ded here  and  there  with  glands  ;  G  G  are  the 
surfaces  of  the  gizzard.  Among  the  higher 
quadrupeds,  the  evidences  of  a  similar  divis- 

Fig.  12.  Fiy.  13. 


Interior  of  stomach  of  African  ostrich.  Stomach  of  dormouse.  Stomach  of  Cape  hyrax. 

ion  of  function  are  presented.     Thus,  in  the  dormouse,  fig.  12,  there  are 
two  compartments  :  a  cardiac,  C,  and  a  pyloric,  P ;  the  same  Digestive  com. 
being  exhibited  more  perfectly  in  the  Cape  hyrax,  Fig.  13.  partments  of 
In  these  -cases  the  cardiac  compartment  is  often  lined  with 
cuticle,  but  the  pyloric  not.     An  increase  in  the  number  of  these  cavities 
occurs  as  the  food  becomes  more  heterogeneous.     In  the  porcupine,  Fig. 
14,  there  are  four,  and  in  the  porpoise,  Fig.  15,  five.     The  stomach  of 

Fig.  14.  Fig.  15.  Fig.  10. 


Stomach  of  porcupine.  Stomach  of  porpoise.  Stomach  of  kangaroo. 

the  kangaroo,  as  shown  in  Fig.  16,  possesses  a  multitude  of  these  cham- 
bers or  compartments,  and  therefore  offers  a  good  illustration  of  the  sub- 
divisions of  stomach  digestion. 

.  IT.  The  case  of  ruminants 

possesses  a  special  inter- 
est. In  these  there-  are 
what  might  be  termed 
four  different  digestive 
chambers,  as  is  shown  in 
Fig.  17,  in  which  a  is  the 

Digestive  cavities  of  a  ruminant.  O3SOphagUS  ;    b,  the  inglu- 


60  DIGESTION   IN  EUMINANTS. 

vies  or  paunch;  c,  the  reticulum  or  honey-comb  stomach;  d,  the  omasum, 
Di  estive  com-  man7plies»  or  third  stomach  ;  e,  abomasum,  reed,  or  fourth 


partments  of  stomach  ;  and  y,  the  pylorus.  The  food,  roughly  triturated 
in  the  mouth,  enters  the  ingluvies,  in  which  it  is  moistened; 
it  then  passes  into  the  honey-comb  or  second  stomach,  which  likewise 
receives  directly  the  water  that  has  been  taken,  and,  after  it  has  been 
thoroughly  moistened  therewith,  it  is  returned  to  the  mouth  in  small 
portions,  to  undergo  a  more  complete  mastication  and  insalivation.  Be- 
ing swallowed  again,  it  is  now  directed  into  the  third  stomach,  from 
which  it  passes  into  the  fourth.  In  this  it  is  submitted  to  a  true  acid 
digestion,  a  gastric  juice  being  secreted  from  the  walls  of  this  cavity.  It 
is  the  mucous  lining  of  this  cavity  which  yields  rennet.  That  these  com- 
plicated motions  and  these  successive  actions  of  the  different  cavities  are 
for  the  purpose  of  preparation  for  the  true  digestion  of  the  fourth  stom- 
ach, is  clearly  proved  by  the  fact  that  in  the  calf  the  milk  passes  directly 
into  the  abomasum. 

Since  fishes  and  water  animals  generally  have  no  salivary  glands,  or 
Digestion  onty  rudimentary  ones,  some  physiologists  have  inferred  that  the 
in  fishes.  use  of  the  saliva  is  for  the  commingling  of  the  food  with  a  due 
portion  of  water.  This  would  reduce  the  importance  of  insalivation  very 
greatly,  and,  indeed,  is  scarcely  consistent  with  the  elaborate  mechanism 
which  has  been  just  described  in  the  case  of  ruminant  animals.  It  is 
worthy  of  remark  that,  even  among  fishes,  there  are  some  which  exhibit 
a  true  rumination,  as,  for  example,  the  carp.  This  is  not  alone  for  the 
purpose  of  resubmitting  the  food  to  the  abrading  action  of  the  pharyngeal 
teeth,  but  likewise  for  commingling  it  with  the  secretion  of  the  pharyn- 
geal cavity. 

In  view  of  the  preceding  facts,  it  may  be  concluded  that,  so  far  from 
there  being  any  thing  in  contradiction  to  the  doctrine  that  different  por- 
tions of  the  digestive  surface  of  the  mucous  membrane  of  the  stomach  are 
devoted  to  different  duties,  there  is  strong  evidence  in  support  of  its  truth, 
derived  partly  frpm  the  instances  furnished  by  comparative  anatomy,  and 
partly  from  the  anatomical  structure  of  the  gastric  mucous  membrane. 
The  four  separate  digesting  chambers  of  the  ruminating  herbivora  are 
merely  an  elaboration  of  the  structure  which  is  presented  by  an  appar- 
ently homogeneous  mucous  surface  in  man.  But  that  this  mucous  sur- 
face is  in  reality  heterogeneous,  and  in  different  regions  possesses  differ- 
ent powers,  is  shown  by  the  fact  that  at  one  part  it  presents  mucous  fol- 
Reo-ionai  func-  ^c^es»  at  another  pepsin  follicles,  at  another  follicles  for  the 
tions  of  human  secretion  of  hydrochloric  acid.  As  we  approach  toward  the 
pylorus,  the  existence  of  a  new  function  is  betrayed  by  the 
appearance  of  a  new  mechanism  —  the  villi,  which  have  been  so  well  stud- 
ied by  Dr.  Neill,  and  this  is  even  indicated  externally  in  the  posterior 


EEGIONAL  DIVISIONS   OF  THE  HUMAN   STOMACH. 


61 


Posterior  view  of  human  stomach. 

of  the  well-known  plicse  fimbriatse. 


Flg' 18'  view  of  the  human  stomach,  Fig. 

18,  showing,  according  to  Profess- 
or Retzius,  that  the  antram  py- 
lori of  the  older  anatomists  is  re- 
ally a  special  compartment  of  the 
general  cavity.  The  figure  is 
derived  from  numerous  examin- 
ations of  the  stomach  in  bodies 
of  middle-aged  women,  and,  as 
represented  at  c  c,  d  d,  indicates 
the  antrum  pylori,  a  being  the 
oesophagus,  b  the  cardiac  orifice. 
The  antrum  pylori  is  distinguish- 
ed by  greater  thickness  of  its  mus- 
cular coat,  more  copious  glandu- 
lar development,  and  the  presence 
The  commencement  of  the  duode- 
num also  forms  a  special  rounded  cavity,  which  Professor  Retzius  pro- 
poses to  name  antrum  duodeni,  characterized  internally  by  the  absence 
of  valvulae  conniventes,  and  by  the  dense  array  of  Brunner's  glands  be- 
neath its  mucous  membrane.  This  part  constitutes  what  has  been  called 
the  fourth  stomach  in  the  porpoise  and  some  other  cetaceans.  The  so- 
called  ligaments  of  the  pylorus  are  connected  with  the  formation  of  the 
antrum  pylori. 

It  has  been  remarked  that  the  first  aim  of  digestion  is  the  procuring  of 
the  food  either  in  a  dissolved  state,  or,  at  all  events,  in  a  con-  Digestion  ac- 
dition  approaching  thereto.  But,  in  .addition  to  this,  pro-  compiishes  so- 
found  changes  in  the  very  nature  of  the  digested  material  metamorphosis 
must,  in  an  incidental  way,  be  constantly  occurring.  Thus  of  the  food- 
the  action  of  saliva  is  to  produce  lactic  acid  from  starch,  and  thus,  in 
the  stomach  itself,  starch  is  transmuted  into  sugar.  In  some  cases  the 
first  stage  of  digestion  seems  to  be  actually  the  reverse  of  what  has  been 
here  set  forth.  Milk,  when  received  into  the  stomach,  undergoes  coagu- 
lation, and,  in  like  manner,  so  also  does  soluble  albumen.  But  these  are 
only  incidental  changes,  the  temporary  solids  thus  produced  soon  lique- 
fying as  proper  digestion  sets  in.  There  is  reason  to  believe  that  all  the 
protein  bodies  are  passed  into  the  condition  of  albuminose,  and  this  though 
they  may  have  been  introduced  in  the  liquid  state.  Even  soups  and 
broths  require  to  be  digested.  A  solution  of  gelatine,  after  G  t . 
it  has  been  in  the  stomach,  refuses  to  gelatinize,  a  solution  ges  of  the  food 
of  albumen  to  coagulate.  The  circumstance  that  gases  may  di^iJons^an?" 
be  evolved  from  digesting  material,  both  in  the  stomach  and  assimilation  of 
intestine,  is  a  sufficient  proof  that  that  material  is  undergoing  water< 


62  USE   OF   COMMON  SALT. 

a  more  or  less  extensive  change.  But  these  changes  are  altogether  insig- 
nificant when  compared  with  those  great  metamorphoses  which  the  nu- 
trient material  passes  through  after  it  has  been  absorbed  from  the  digest- 
ive cavities ;  and  doubtless,  at  the  most,  they  are  only  mere  subdivisions, 
of  which  the  splitting  of  the  sugar  or  starch  atom  into  lactic  acid  may  be 
taken  as  the  type,  or  mere  unions  with  water,  of  which  the  passage  of 
cane  sugar  into  milk  sugar  is  an  example. 

The  gastric  juice,  therefore,  not  only  dissolves,  but  also,  in  an  incipient 
Production  of  an<l  indirect  manner,  modifies  the  food.  Protein  bodies  and 
peptones.  gelatinous  matters  yield  substances  after  its  action  of  the 
same  composition  as  their  own,  but  with  different  physical  and  chemical 
properties,  being  readily  soluble  in  water,  and  even  in  diluted  alcohol,  and 
not  forming  insoluble  compounds  with  metalline  salts.  By  Lehmann, 
who  has  examined  these  substances,  they  have  been  designated  as  pep- 
tones ;  and  since  they  may  arise  without  the  evolution  or  absorption  of 
any  gas,  and  the  quantity  of  sulphur  they  contain  is  the  same  as  that  in 
the  bodies  from  which  they  were  derived,  he  infers  that  the  action  is  real- 
ly an  assimilation  of  water,  the  other  ingredients  remaining  unchanged. 

Turning  our  attention  now  to  the  origin  of  the  gastric  juice,  it  is  inter- 
esting; to  observe  the  economical  manner  in  which  its  hydro- 
Use  and  man-  .  .  .  ,  . 
agement  of  chloric  acid  element  is  managed.  To  the  proper  understanding 
jommon  s  t.  Q£  ^j^  ^  js  necessary  to  anticipate  what  will  have  to  be  more 
fully  considered  in  describing  the  bile,  a  uniform  ingredient  of  which  is 
the  oxide  of  sodium,  or  soda.  The  hydrochloric  acid  of  the  gastric  juice 
and  the  soda  of  the  bile  are  derived  from  the  same  source — common  salt, 
which  is  either  present  in  the  food,  or  purposely  added  as  a  condiment. 
It  undergoes  decomposition  easily,  yielding  the  two  products  specified, 
that  is,  hydrochloric  acid  and  soda,  and  is  readily  formed  by  the  reunion 
of  these  substances. 

There  exists  in  the  action  of  the  kidneys  a  special  provision  for  prevent- 
ing the  quantity  of  chloride  of  sodium  present  in  the  blood  from  rising 
over  41  parts  in  10,000.  This,  of  course,  controls  the  amount  diffused 
through  the  tissues.  The  necessity  of  such  a  regulation  becomes  appar- 
ent when  we  consider  that  the  rate  of  the  solubility  of  albumen  and  ca- 
sein in  water  is  governed  by  the  presence  of  that  substance,  as  is  also  the 
quickness  with  which  the  coagulation  of  fibrin  takes  place,  and  the  re- 
pair of  the  waste  of  the  muscles. 

Common  salt  introduced  into  the  system  undergoes  decomposition, 
furnishing  hydrochloric  acid  to  the  gastric  juice,  and  soda  to  the  bile. 
Considering  the  large  quantity  of  these  secretions  produced  in  a  short 
space  of  time,  it  is  clear  that  the  drain  of  common  salt  must  be  great — 
not  less  than  a  third  of  an  ounce  a  day ;  yet  the  quantities  consumed,  at 
most,  are  only  small. 


SUMMARY  OF  DIGESTION.  63 

How,  then,  is  this  to  be  explained?  Assuredly  there  is  no  other 
source  from  which  these  bodies  can  come  than  the  one  indicated — the 
common  salt,  and  yet  it  seems  to  be  totally  inadequate. 

I  think  that  this  difficulty  ?s  rather  imaginary  than  real.  Things  are 
so  arranged  that  a  limited  quantity  of  salt  can  produce  unlimited  quanti- 
ties of  gastric  juice  and  bile ;  for  the  former,  associated  with  the  food  it 
has  digested,  scarcely  escapes  from  the  pyloric  valve  before  it  encounters 
the  bile  and  pancreatic  juices  discharging  into  the  duodenum,  and  through 
the  length  of  the  upper  portion  of  the  small  intestines  these  secretions, 
together  with  the  food  they  have  acted  upon,  are  brought  into  complete 
contact.  The  reproduction  of  chloride  of  sodium  is  therefore  constantly 
taking  place  in  intestinal  digestion,  and  it  returns  back  to  the  system 
through  the  absorbents.  Again  it  undergoes  decomposition,  its  acid  re- 
appearing in  the  gastric  juice,  and  its  alkali  in  the  pancreatic  juice  and 
bile.  By  thus  using  a  small  amount  over  and  over  again,  great  effects 
can  be  produced,  and  it  is  then  only  necessary  to  restore  those  small  por- 
tions that  are  wasted  in  carrying  out  the  general  scheme. 

In  the  low-pressure  marine  steam-engine  we  have  an  example  of  the 
same  kind.  A  certain  quantity  of  water  is  vaporized  in  the  boiler  and 
condensed  in  the  engine ;  pumped  back  into  the  boiler  to  be  vaporized, 
arid  then  recondensed  in  the  engine.  Comparatively  little  is  required  to 
supply  the  wants  of  the  machine,  and  long  voyages  can  be  made  with 
only  as  much  water  as  will  compensate  for  the  necessary  waste  arising 
in  the  working. 

For  the  sake  of  presenting  the  consideration  of  the  function  of  diges- 
tion with  clearness,  it  is  customary  to  leave  out  of  consider-  Stomach  di 
ation  the  subordinate  actions  taking  place  both  in  the  stom-  gestion  is  his- 
ach  and  intestine.     This,  however,  involves  a  certain  amount  JeftlnafdLes- 
of  error,  since  respiratory  or  non-nitrogenized  digestion  oc-  tion  is  caiorifa- 
cuf  s  in  the  former  cavity,  and  nutritive  or  nitrogenized  in  the 
latter.     Nevertheless,  there  can  be  no  doubt  that  if  our  view  is  restricted 
to  the  more  imposing  characters,  we  are  justified  in  accepting  the  dogma 
that  "  stomach  digestion  is  histogenetic  or  nitrogenized,  and  intestinal 
digestion  is  calorifacient." 

Under  the  most  comprehensive  point  of  view,  examining  the  action  of 
the  entire  digestive  tract  from  the  mouth  to  the  rectum,  we  General  sum. 
discover  a  recurrent  periodicity.     In  the  mouth,  the  transi-  mary  of  diges- 
tory  digestion  taking  place  is  wholly  expended  upon  the  ca- 
lorifacient food ;  in  the  stomach  it  is  the  nutritive  portion  which  is  chiefly 
attacked ;  in  the  duodenum  there  is  a  return  to  the  calorifacient,  and  in 
the  ccecum  of  animals  a  resumption  of  the  nutritive.     This  last  is  less 
apparent  in  man,  for  in  him  the  ccecum  exists  only  in  a  rudimentary  state, 
represented  by  the  appendix  vermiformis. 


64  DIGESTION   OF   GELATINE. 

As  the  alteration  takes  place  from  calorifacient  to  nutritive  digestion, 
the  active  fluid  changes  its  chemical  relations.  In  the  mouth  and  duo- 
denum, alkaline  juices  are  resorted  to ;  in  the  stomach  and  coecum,  acid 
ones.  Whenever  there  is  an  accidental  inversion  of  these  conditions,  the 
result  correspondingly  changes ;  so  when  bile,  which  is  alkaline,  regur- 
gitates into  the  stomach,  the  digestion  of  nutritive  food  is  instantly  ar- 
rested. 

In  each  of  these  cases  the  object  is  the  same:  it  is  to  obtain  the  nutri- 
ent material  under  such  forms  that  the  absorbent  vessels  can  readily  take 
it  up ;  this,  as  we  have  seen,  often  involves  a  metamorphosis  of  the  ele- 
ments of  the  food  where  mechanical  subdivision  would  be  insufficient. 
Fibrin  has  to  be  brought  into  a  soluble  state,  and,  indeed,  albumen  itself 
must  be  modified.  If  it  has  been  taken  uncoagulated  or  glairy,  it  be- 
comes opalescent,  and  passes  into  the  allied  form  known  as  albuminose. 
In  this  condition  it  is  neither  precipitated  by  heat  nor  by  nitric  acid, 
though  it  is  by  corrosive  sublimate.  The  cause  of  this  transformation 
probably  has  reference  to  the  relative  facility  with  which  albuminose  can 
transude  into  the  venous  capillaries  compared  with  albumen. 

There  is  thus  reason  to  suppose  that  the  result  of  stomach  digestion 
is  the  reduction  of  the  various  nitrogenized  constituents  of  the  food  to 
the  condition  of  albuminose.  It  is  plain  that  fibrin  must  come  into  this 
or  some  analogous  condition,  for  it  can  not  be  absorbed  as  fibrin,  and,  ac- 
cordingly, it  is  found  that  the  blood  of  the  gastric  and  mesenteric  veins 
abounds  in  albuminose. 

Intermediate  between  the  classes  of  calorifacient  and  histogenetic  food, 
Case  of  gela-  belonging,  by  its  composition  and  conditions  of  digestion,  to 
tine-  the  latter,  but  by  the  function  it  discharges  to  the  former,  is 

gelatine,  a  nitrogenized  substance.  It  appears  to  be  always  derived  from 
albumen,  and  any  portion  which  may  have  been  received  in  the  food  is 
never  directly  assimilated  or  used  for  the  fabrication  of  tissue,  but  solely 
ministers  to  the  production  of  heat.  Though  thus  a  calorifacient  body, 
its  place  of  digestion  is  the  stomach.  After  it  has  suffered  the  action  of 
that  organ  it  has  lost  its  power  of  gelatinizing,  can  no  longer  be  precip- 
itated by  chlorine,  nor  give  the  leather  precipitate  with  tannin.  The  use 
of  it  under  the  form  of  jellies,  soups,  etc.,  is  always  attended  with  the  ap- 
pearance of  an  unusual  quantity  of  urea  in  the  urine,  and  hence  the  ad- 
ministration of  those  domestic  preparations,  under  an  idea  of  their  great 
nutritive  value,  is  to  be  looked  upon  as  only  a  popular  error.  In  an  in- 
direct way,  however,  under  the  conditions  of  restricted  diet,  usually  met 
with  in  the  sick-room,  gelatine  doubtless  maintains  an  interesting  relation 
to  the  albumenoid  bodies  in  this,  that  it  protects  them  from  destruction 
by  undergoing  oxidation  itself,  and  so  satisfying  the  requirements  of  the 
respiratory  mechanism  ;  for,  were  there  not  such  a  substance  present  to 


EELATIVE  DIGESTIBILITY   OF   FOOD.  65 

receive  the  attack,  the  respired  oxygen  would  rapidly  bring  on  the  waste 
of  the  proper  nitrogenized  tissues. 

In  relation  to  the  gelatigenous  tissues,  it  may  be  remarked  that  gela- 
tine is  not  an  actual  constituent  of  them,  but  arises  from  them  Gelatine  not 
by  boiling  with  water.  By  a  like  process,  sufficiently  pro-  £e^n^ 
longed,  a  similar  substance  may  be  obtained  from  cartilage,  ent. 
designated  cartilage-gelatine,  or  chondrine.  In  these  cases  the  material 
unites  with  water  in  the  same  manner  that  starch  does  in  producing  glu- 
cose. 

The  food  must  therefore  pass  through  various  stages  before  it  can  be 
fitted  for  introduction  into  the  circulation,  and  carried  to  all  parts  of  the 
system.  It  is  procured  in  portions  of  a  suitable  size  either  by  the  fin- 
gers, or,  in  civilized  life,  by  resorting  to  artificial  implements,  the  knife 
and  fork.  The  incisor  teeth  next  cut  it  up,  and  the  molars  crush  or  grind 
it,  being  worked  for  this  purpose  by  a  powerful  system  of  muscles  ;  mean- 
time it  is  incorporated  with  saliva  and  atmospheric  air.  Passing  into 
the  stomach  under  the  condition  of  a  coarse  pulpy  mass,  the  gastric  juice 
carries  the  process  still  farther,  a  more  intimate  disintegration  of  its 
structure  ensues,  and  it  is  eventually  brought  into  a  soluble  and  changed 
form.  The  time  required  to  produce  this  effect  varies  with  Dio.estibilit 
the  nature  of  the  food.  Thus  it  has  been  noticed  that  beef  of  different  ar- 
is  much 'more  quickly  acted  on  than  mutton,  and  mutton  t] 
sooner  than  pork. 

Statements  respecting  the  digestibility  of  different  articles  of  food 
must,  however,  be  received  with  many  restrictions.  If,  as  circumstances 
the  earlier  physiologists  believed,  the  stomach  was  the  sole  interfering 
digestive  cavity,  and  the  intestine  only  for  the  purpose  of  ab-  Of  digestibiii- 
sorption,  they  would  doubtless  be  much  nearer  to  the  truth.  t7- 
But  when  we  recall  that  the  digestion  of  fats  does  not  even  begin  until 
the  intestine  is  reached,  and  that  the  digestion  of  the  nitrogenized  sub- 
stances is  only  in  part  accomplished  by  the  gastric  juice,  but  goes  on 
under  the  influence  of  the  intestinal  juice  throughout  the  whole  length  of 
the  small  intestine,  we  see  at  once  how  imperfect  and  even  incorrect  are 
the  indications  afforded  by  such  experiments  as  those  of  Spallanzani, 
who  introduced  food  articles  into  the  stomach  through  the  oesophagus  in 
perforated  silver  vessels,  or  those  of  Beaumont,  who  availed  himself  of  a 
gastric  fistula.  Neither  can  we  take,  in  all  instances,  the  time  which  an 
article  of  food  will  remain  in  the  stomach  as  a  measure  of  its  digestibil- 
ity, for  this  is  known  to  vary  with  many  conditions,  as,  for  instance,  the 
quantity  introduced  at  a  time,  and  the  condition  of  the  organ  itself.  As 
general  illustrations  of  the  digestibility  of  some  of  the  ordinary  elements 
of  food,  the  examples,  however,  being  more  or  less  open  to  the  preceding 
criticisms,  the  following  facts  may  be  offered.  The  white  of  an  egg,  rep- 

E 


66  RELATIVE   DIGESTIBILITY   OF   FOOD. 

resenting  soluble  albumen,  if  introduced  into  the  stomach  of  a  fasting  dog 
through  a  gastric  fistula,  will  disappear  in  less  than  an  hour ;  but  if  the 
whites  of  eight  eggs  be  introduced,  portions  thereof  can  be  recognized 
after  four  hours.  Lehmann,  who  made  these  observations,  adds  that 
blood  fibrin  varies  in  its  time  for  gastric  solution  according  as  it  is  in  a 
finely  comminuted  or  a  massive  state ;  in  the  former  instance  disappear- 
ing from  the  stomach  of  a  dog  in  an  hour  and  a  half,  but  the  same  weight 
in  the  latter  condition  requiring  almost  twice  the  time.  Coagulated  al- 
bumen indicates  the  commencement  of  digestion,  and  even  its  local  com- 
pletion, in  from  five  minutes  to  a  quarter  of  an  hour ;  but  here  again  much 
depends  on  the  condition  of  the  stomach  and  the  general  state  of  the  sys- 
tem, whether  the  animal  has  been  fasting,  and  whether  the  gastric  juice 
is  exuding  in  a  dilute  or  concentrated  state. 

So  far  as  such  examinations  go,  they  do  not  exhibit  any  marked  dif- 
Kespiratory  di-  ference  between  albumen,  fibrin,  and  casein.  Gelatine,  how- 
gestion,  as  of  ever>  {s  acted  on  with  remarkable  rapidity.  Beaumont  ob- 
gln  in  the  served  that  in  an  hour  150  grammes  of  jelly  had  disappeared, 
stomach.  The,  experiments  which  have  been  made  on  the  digestibility 

of  vegetable  food  introduced  through  gastric  fistula?  are  obviously  of  no 
use,  since  the  chief  constituents  thereof,  such  as  starch  and  fat,  are  not 
even  influenced  in  those  circumstances  until  they  have  reached  the  intes- 
tine. Their  passage  from  the  stomach  in  this  unchanged  state,  or 
changed  only  so  far  as  their  nitrogenized  ingredients  are  concerned,  may 
teach  us  the  important  fact,  which  should  in  these  inquiries  be  always 
borne  in  mind,  that  disappearance  from  the  stomach  is  one  thing  and  di- 
gestion another,  and  that  even  though  a  substance  may  have  passed  the 
pyloric  valve,  its  digestion,  far  from  having  been  completed,  may  not  as 
yet  have  commenced. 

The  digestion  of  nutritive  or  nitrogenized  material — histogenetic  diges- 
tion— is  therefore  carried  on  in  the  stomach  mainly ;  and  though  first 
mechanical,  and  then  chemical  agencies  are  resorted  to,  the  object  is 
throughout  the  same — to  obtain  the  food  in  such  a  divided  and  changed 
state  that  it  can  pass,  dissolved  in  water,  into  the  capillary  vessels. 


INTESTINAL   DIGESTION.  67 


CHAPTER  IV. 

OF  CALORIFACIENT  OB  INTESTINAL  DIGESTION. 

Nature  of  Intestinal  Digestion. — Structure  of  the  Intestine. — Digestive  Fluids  of  the  Intestine. — 
The  Pancreatic  Juice. —  The  Enteric  Juice. — Juice  of  Lieberkuhn. — Secretion  of  Peyer's 
Glands. — Bik. — Digestion  of  the  Carbohydrates  and  Hydrocarbons. ^-Properties  and  Varie- 
ties of  Lactic  Add. — Doctrine  of  the  Effects  of  Acidity  and  Alkalinity  of  the  Digestive  Juices. 
— Illustration  of  Intestinal  Digestion  from  the  making  of  Wine. — MaJdng  of  Bread. — Influence 
of  Heat  over  Ferments. —  Comparison  of  Gastric  and  Intestinal  Digestion. —  Changes  of  the  In- 
testinal Contents. — The  Fozcal  Residues. 
• 

AFTER  the  chyme  formed  in  the  stomach  has  passed  through  the  py- 
loric  valve  into  the  small  intestine,  the  influence  of  the  gastric  juice 
continues  for  a  certain  time,  even  after  the  bile  and  pancreatic  juices 
have  been  reached.  Since  their  action  must  be  necessarily,  in  the  first 
instance,  superficial,  the  interior  of  the  mass  is  still  undergoing  stomach 
digestion. 

But,  setting  aside  this  incidental  result,  which  at  the  most  can  not  be 
of  long  duration,  the  digestive  operation  taking  place  in  the   ^ature  of  in 
part  of  the  intestinal  tract  now  under  consideration  is  di-  testinai  diges- 
rected  to  the  heat-making  food. 

The  organ  in  which  calorifacient  digestion  takes  place  may  be  de- 
scribed as  a  tube  bounded  by  two  valves,  the  pyloric  above  structure  of 
and  the  ileo-coecal  below.  Its  length  may  be  estimated  at  the  intestine, 
about  twenty  feet.  The  digestive  surface,  making  a  due  allowance  for 
its  increase  by  reason  of  its  valvular  structure  presently  to  be  described, 
can  not  be  much  under  3500  square  inches.  The  dimensions  of  the  ca- 
lorifacient digesting  surface  are  therefore  far  rreater  than  those  of  the 
nutritive. 

The  interior  and  acting  portion  of  this  tube  presents  two  different 
systems  of  apparatus,  and  is  occupied  in  the  discharge  of  two  D 
totally  distinct  functions,  digestion  and  absorption.     It  is,  ratus  of  intes- 
perhaps,  this  double  duty  which  demands  so  extensive  a  sur-  tine' 
face,  and  not  the  necessities  of  heat-making  digestion  alone. 

Like  the  stomach,  this  tube  consists  of  three  coats— a  serous,  a  mus- 
cular, and  a  mucous.  The  latter  is  gathered  up  in  its  inte-  . 

.  11  •       •        c  11          i          11  ,  Action  of  the 

nor  into  numberless  projecting  folds — the  valvular  conniven-  vaivuise  conni- 
tes.     These  serve  to  increase  the  surface  to  which  the  food  ventes- 
is  exposed,  and  perhaps  afford  a  mechanical  obstacle  to  its  passing  too 
quickly  forward.     They  tend  also  to  break  the  continuous  motion,  and 
bring  the  interior  parts  of  the  chyme  to  the  surface.     The  onward  move- 


68  INTESTINAL  DIGESTIVE   FLUIDS. 

ment  is  of  course  due  to  the  pressure  exerted  conjointly  by  the  straight 
and  circular  fibres  of  the  muscular  coat.  Anatomists  divide  the  tube 
into  three  portions — the  duodenum,  jejunum,  and  ileum. 

Fig.  19.  In  Fig.  19  we  have  a  pos- 

terior view  of  the  duodenum, 
a  being  its  superior  or  pyloric 
extremity,  b  the  middle  por- 
tion, o  the  jejunum,  d  the  gall- 
bladder, i  the  cystic  duct,  p 
hepatic  duct,  c  the  ductus  com- 
munis,  m  pancreatic  duct. 

Soon  after  the  chyme  has 
escaped   through  .the   pyloric 
valve  into  the   duodenum,  it 
Posterior  view  of  the  duodenum.  comes  under  the  influence  of 

the  bile  and  pancreatic  juices,  which  are  sometimes  discharged  upon  it 
at  a  common  point,  and  sometimes  at  a  little  distance  apart. 

Digestive  flu-  r  ,      .     . 

ids  of  the  in-  Almost  simultaneously  it  is  submitted  to  the  mechanical  ac- 
tion of  the  valvula?  conniventes,  which  make  their  appearance 
in  the  vertical  portion  of  the  duodenum,  and  continue  in  large  numbers 
until  within  the  last  two  or  three  feet  of  the  end  of  the  tube.  As  the 
intestine  is  distended,  these  project  w4th  a  certain  degree  of  turgidity, 
and  accomplish  their  mechanical  object. 

But,  besides  the  pancreatic  and  biliary  fluids,  there  are  other  juices 
thrown  upon  the  passing  chyme — the  enteric  juice,  which  comes  from 
Brunner's  glands,  and  a  liquid  oozing  from  the  follicles  of  Lieberkuhn. 
Moreover,  the  organisms  known  as  Peyer's  glands  are  affecting  the  con- 
tents of  the  tube.  Of  each  of  these  it  is  necessary  therefore  to  speak. 

1st.  The  pancre'atic  juice,  secreted  by  the  pancreas,  an  organ  bearing  a 
Pancreatic  resemblance  in  its  anatomical  construction  to  the  salivary 
tioneandnprop-  glan^s>  an(*  hence  usually  regarded  as  one  of  that  group. 
erties  of.  The  juice  itself  is  analogous  to  saliva,  being  viscid,  and  in  its 

reaction  alkaline:  its  specific  gravity  is  about  1.008.  Alcohol  coagulates 
it.  It  is  said  to  contain  no  sulphocyanide  nor  any  suspended  particles. 
It  acts  upon  starch  even  more  energetically  than  saliva,  transmuting  it 
into  sugar  and  lactic  acid,  and  upon  fats  by  forming  them  into  an  emul- 
sion, so  that  they  are  readily  absorbed.  This  has  been  found  to  take 
place  in  artificial  experiments  by  submitting  fat  substances  to  the  juice 
at  a  temperature  of  100°. 

Constitution  of  Pancreatic  Juice  of  Dog.     (From  Schmidt.') 

Water 900.76 

Organic  matter 90.38 

Inorganic    "     8.86 

1000.00 


ENTEEIC   JUICE   AND   SECRETION   OF   LIEBERKUHN. 


69 


As  would  be  inferred  from  the  difference  of  emulsifying  power  between 
the  saliva  and  tjiis  juice,  its  organic  matter  differs  from  ptyaline.  It  is 
estimated  that  the  standard  secretion  of  it  is  from  five  to  seven  ounces 
per  diem. 

The  action  of  the  pancreatic  juice  appears  to  be  limited  to  the  upper 
half  of  the  intestine,  for  it  is  in  that  region  only  that  butyric  acid  is  de- 
veloped from  butter. 

2d.  The  enteric  juice  is  secreted  by  the  organs  known  as  Brunner's 
glands,  the  structure  of  which  has  a  certain  analogy  to  the 

T  i   TM       •       i  -ITI         11  IT  Enteric  juice. 

preceding,  and,  like  it,  these  doubtless  belong  to  the  salivary 
group.  Brunner's  glands  occur  chiefly  in  the  upper  part  of  the  small  in- 
testine, presenting  themselves  in  the  submucous  tissue  thereof  as  little 
bodies,  commonly  compared  by  anatomists  to  hemp-seeds.  They  consist 
of  lobules  with  ducts  communicating  with  a  common  outlet.  Their  se- 
cretion possesses  a  more  energetic  power  when  mixed  with  bile  and  pan- 
creatic juice,  than  the  pancreatic  juice  alone,  in  producing  fatty  emulsions. 
In  the  opinion  of  Bidder  and  Schmidt,  the  intestinal  juice,  which  they 
describe  as  being  invariably  alkaline,  not  only  metamorphoses  starch  as 
Fig.  20.  rapidly  as  the  saliva  or  pancreatic  juice,  but 

also  exerts  as  powerful  an  action  on  flesh, 
albumen,  and  other  protein  bodies  as  that 
which  occurs  in  the  stomach  itself. 

In  Fig.  20,  which  is  a  half  diagram  of 
one  of  these  glands,  a  a  represents  the  mu- 
cous surface  of  the  intestine,  and  b  the 
lobulated  gland,  discharging  its  secretion 
through  a  common  duct. 

3d.  The  secretion  of  the  follicles  of  Lieberkuhn,  which,  as  shown  in 
Fig.  21,  are  straight,  narrow  coecal  de-  Secretion  of 
pressions  of  the  mucous  membrane,  found  follicles  of 
all  over  the  small  intestine,  and  in  a  gen-  Lieberkuhn- 
eral  manner  analogous  to  the  tubular  follicles  of  the 
stomach.  Their  interior  is  lined  with  columnar 
epithelium,  and  in  depth  they  are  equal  to  the  thick- 
ness of  the  mucous  membrane,  their  closed  ends  be- 
ing therefore  in  contact  with  the  submucous  tissue, 
and  their  mouths  opening  into  the  intestine.  In  a 
state  of  health  they  contain  a  clear  mucus-like  secre- 
tion. In  inflammations  of  the  part  they  are  filled 
with  a  more  opaque,  whitish  liquid.  From  their  re- 
semblance to  the  follicles  of  the  stomach  which  secrete  pepsin,  it  may  be 
presumed  that  they  possess  a  somewhat  similar  function;  but  in  the 
stomach,  the  resulting  secretion  is  brought  in  relation  with  acids  ;  in  the 


Diagram  of  Brunner's  glands. 


Fig.  21. 


Diagram  of  follic 
kuhn. 


of  Lieber- 


70  PETER'S  BODIES  AND  THE-  BILE. 

intestine,  with  alkaline  bodies  ;  and  hence  the  physiological  action  may 
differ  in  the  two  positions,  though  the  structure  and  primary  function 
may  be  the  same. 

4th.  The  secretion  of  Peyer's  glands.  These  may  be  described  as  cir- 
Secretion  from  cular  spots,  of  a  whitish  color,  and  about  the  tenth  of  an  inch 
Peyer's  glands.  jn  diameter,  constituting  glandular  patches  full  of  cell  germs, 
but  without  any  excretory  duct  opening  into  the  intestine.  It  is  sup- 
posed that  they  discharge  their  contents  by  rupturing  at  a  certain  stage 
of  their  development.  The  solitary  and  agminate  glands  appear  to  be- 
Ftg.  22.  long  to  the  same  physiological  group. 

The  two  conditions  of  the  Peyerian  glands 
are  shown  in  Fig.  22,  the  right  one  being 
empty,  its  contents  having  been  discharged, 
the  left  one  still  full.  By  some  it  is  denied 
that  these  bodies  are  connected  with  intes- 
tinal digestion.  The  facts  that  vascular 
loops  pass  into  their  granular  contents,  and 
Peyenan  glands.  that  the  lacfeals  bear  a  definite  relation  to 

them,  seem  to  indicate  that  they  are  rather  portions  of  the  absorbent 
mechanism. 

5th.  The  bile.  Of  this  it  is  not  now  necessary  to  give  a  detailed 
description,  since  that  will  occur  more  appropriately  in  treat- 
ing of  the  functions  of  the  liver.  For  the  present  purpose,  it 
is  sufficient  to  state  that  bile  is  a  greenish-yellow  liquid,  of  bitter  taste 
and  alkaline  reaction.  It  is  soluble  in  water,  changes  with  rapidity 
under  the  influence  of  the  air,  or  even  spontaneously.  Its  specific  grav- 
ity is  about  1.028.  An  ultimate  analysis  of  its  organic  material  shows 
C76,  H66,  O22,  N2,  with  sulphur.  Its  aspect  is  therefore  that  of  a  hydro- 
carbon, and  it  stands  in  strong  contrast  with  the  nitrogenized  bodies. 
It  is  a  significant  fact  that,  even  in  the  lower  tribes  of  life,  it  is  uniformly 
discharged  into  the  upper  part  of  the  intestine.  Bidder  and  Schmidt 
estimate  the  diurnal  quantity  of  bile  at  54  ounces,  containing  5  per 
cent,  of  solid  matter ;  they  also  give  the  following  table  of  the  diurnal 
amounts  of  the  various  digestive  fluids  secreted  by  a  man  of  the  stand- 
ard weight,  140  pounds : 

Diurnal  Amount  of  Digestive  Secretions. 

Saliva 3.30  Ibs.,  containing  solid  matter  1.  per  cent. 

Bile 3.30     "  "  "         "       5.         " 

Gastric  Juice 14.08     "  "  "         "      3.         " 

Pancreatic  Juice ...       .44     "  "  "         "         .1       " 

Intestinal  Juices  ...       .44     "  "  "         "       1.5       " 

The  bile  does  not  appear  to  exert  any  agency  in  effecting  the  digestion 
of  either  nitrogenized  or  amylaceous  bodies.     The  period  of  its  max- 


POWER   OF   PANCREATIC   JUICE.  71 

imum  production,  which  is  13  or  14  hours  after  a  meal,  does  not  coincide 
with  the  period  of  most  energetic  digestion. 

With  these  statements  of  the  nature  of  the  various  juices  which  pass 
into  the  small  intestine,  we  may  proceed  to  investigate  the  phenomena 
of  the  digestion  carried  on  in  that  tube. 

In  1832,  Dr.  Bright,  to  whom  medicine  is  so  much  indebted  for  his 
discoveries  in  relation  to  the  pathology  of  the  kidney,  pub-  Emulsifvin(r 
lished  three  cases  of  disease  of  the  pancreas,  attended  by  the  power  of  pan- 
appearance  of  a  large  quantity  of  fat  in  the  faeces,  and  drew  c 
the  inference  that  in  such  morbid  states  the  fats  are  imperfectly  digested. 
More  recently,  M.  Bernard  has  published  experimental  evidence  to  prove 
that  the  digestion  of  the  fats  consists  in  bringing  them  into  the  condition 
of  an  emulsion,  and  that  the  pancreatic  juice  accomplishes  this  object. 

Whatever  influence  the  pancreatic  and  enteric  juices  can  exert  on 
starch  and  oil  outside  of  the  body,  in  artificial  experiments,  they  un- 
doubtedly exert  it  in  the  small  intestine  as  long  as  the  temperature  is 
the  same.  On  starch,  the  action,  as  has  already  been  stated,  is  to  effect 
its  conversion  into  sugar,  and  then  into  lactic  acid.  The  oils  are  turned 
into  emulsions.  The  constitutional  relation  between  starch  and  lactic 
acid  is  such,  that  if,  in  presence  of  water,  one  atom  of  the  gubdivision  Of 
former  be  equally  and  systematically  split  or  divided  into  starch  into  lac- 
two  portions,  those  portions  are  atoms  of  lactic  acid.  And 
since  this  substance  contains  no  nitrogen,  its  oxidation  either  artificially 
or  in  the  interior  of  the  system  gives  origin  to  carbonic  acid  and  water 
— bodies  which  can  at  once  b«  removed  by  the  action  of  the  skin,  or  the 
lungs,  or  the  kidneys. 

Respecting  the  digestion  of  the  carbohydrates — cellulose,  gum,  starch, 
and  the  different  kinds  of  sugars,  it  may  be  remarked,  that  eel-   Digggfon  of 
lulose,  of  which  the  pith  of  elder  is  an  example,  and  which   the  carbohy- 
occurs  in  a  pure  form  in  Swedish  filtering-paper,  not  only  re- 
sists, in  artificial  experiments,  the  action  of  the  digestive  juices,  but  also 
it  would  appear  to  do  so  naturally  in  the  higher  tribes,  and  hence  it  is 
abundantly  found  in  the  excrement  of  the  herbivora.     To  this  statement, 
perhaps,  however,  the  case  of  the  beaver  affords  an  exception,  Digestion  of 
there  being  reason  to  suppose  that  this  animal  possesses  the  cellulose, 
power  of  digesting  cellulose. 

There  can  be  no  doubt,  moreover,  that  many  insects  have  the  same 
power,  for  chitin,  which  may  be  obtained  from  their  wing-cases,  and  which 
retains  the  appearance  of  the  structure  of  the  part,  may  be  considered  as 
cellulose  united  with  a  nitrogenized  body,  having  the  constitution  of  in- 
sect muscular  fibre.  This  substance  not  only  constitutes  the  skeleton 
of  insects,  their  scales,  hairs,  and  enters  into  the  construction  of  their 
tracheae,  but  even  forms  one  of  the  coats  of  their  intestinal  canal.  Since 


72  DIGESTION  OF   CAEBOHYDEATES. 

it  does  not  appear  that  they  can  metamorphose  other  carbohydrates  into 
this  body,  we  may  infer,  as  would  indeed  seem  probable,  considering  the 
nature  of  the  food  of  many  of  them,  that  they  can  digest  woody  fibre. 
The  digestive  apparatus  of  man,  however,  can  not  exert  such  a  power. 

Neither  does  it  appear  that  gum  undergoes  either  digestion  or  absorp- 
Digestion  of  ti°n'  In  artificial  experiments  it  also  resists  the  action  of  di- 
gum.  gestive  fluids,  and  is  not  changed  when  present  during  the 

fermentation  of  other  bodies,  even  though  its  exposure  thereto  be  contin- 
ued for  several  days.  Administered  to  animals,  it  is  almost  entirely 
voided  with  the  excrement.  Thus  Boussingault,  having  given  to  a  duck 
fifty  grammes  of  gum-arabic,  obtained  forty-six  grammes  from  the  ex- 
crements in  nine  hours.  In  an  experiment  upon  an  old  rabbit,  to  which, 
with  a  diet  of  cabbage-leaves,  ten  grammes  of  gum-arabic  were  daily  given 
by  Lehmann,  the  gum  being  administered  in  solution  in  water  by  injec- 
tion into  the  stomach,  no  trace  whatever  of  gum  could  be  detected  in 
the  urine,  none  in  the  chyle  of  the  thoracic  duct,  and  none  in  the  blood, 
but  it  was  easily  enough  recognized  in  the  excrement.  From  this  he 
infers  that  the  preparations  of  gum,  which  are  such  favorite  medicines 
with  some  physicians,  yield  to  the  animal  organism  only  an  extremely 
small  quantity  of  material  of  a  nature  to  support  the  respiratory  process, 
and  that  their  uses,  if  they  are  of  any  use,  can  be  merely  negative  in 
acute  diseases. 

Of  the  carbohydrates,  starch  is  perhaps  the  most  important,  occurring 
Digestion  of  as  ^  does  in  abundance  in  vegetable  food.  It  can  not  be  made 
starch.  use  Of  jn  ^he  system  without  fifst  being  transmuted  into  dex- 
trine, sugar,  and  eventually  lactic  acid,  these  changes  being  greatly  ex- 
pedited if  it  has  been  previously  prepared  by  boiling  in  water,  or  other 
equivalent  operations  of  cooking.  The  saliva  commences  the  action, 
which  in  man  is  even  prolonged  in  the  stomach,  and  in  the  herbivora  still 
more  decisively  in  the  paunch,  in  birds  in  the  crop.  On  gaining  the  stom- 
ach, the  farther  transmutation  of  the  starch  is  arrested  by  the  gastric 
juice,  but  after  reaching  the  duodenum  it  is  resumed  with  greater  energy 
than  ever,  under  the  influence  of  the  pancreatic  juice.  Reaching  the  ile- 
um,  the  intestinal  juice  continues  the  action,  though  with  less  vigor.  In 
this  passage  to  the  large  intestine,  the  starch  is  gradually  assuming  the 
condition  of  dextrine  and  sugar,  the  former  substance  passing  into  the 
latter  with  such  facility  that  it  can  only  be  recognized  transiently. 
Doubtless  the  sugar  thus  arising  is  in  great  part  directly  absorbed,  though 
some,  before  the  ccecum  is  reached,  is  transmuted  into  lactic  acid,  and  oth- 
er portions,  after  passing  through  the  ileo-coecal  valve,  into  butyric  acid. 

From  what  has  been  observed  respecting  starch,  it  may  be  inferred  how 
Digestion  of  important  sugar  is,  since  through  the  condition  of  sugar  alone 
sugar.  is  starch  available  for  the  uses  of  the  system.  It  is  to  be  rec- 


DIGESTION  OF  SUGAR.  73 

ollected,  however,  that  sugar  itself  is  only  an  intermediate  or  transitory 
stage,  through  which  the  carbohydrate  is  passing,  a  consideration  which 
explains  the  circumstance  that  it  does  not  occur  even  in  the  portal  blood 
to  such  an  extent  as  might  be  expected,  nor  yet  in  the  chyle.  Some 
have  been  led  to  infer  from  these  facts  that  this  substance,  like  gum,  is 
in  reality  only  very  tardily  absorbed,  an  opinion  which  they  suppose  to 
be  strengthened  by  the  circumstance  that  glucose  or  any  other  kind  of 
sugar,  introduced  into  the  jugular  vein,  runs  through  the  course  of  the 
circulation,  and  is  secreted  unchanged  by  the  kidneys.  But  it  is  to  be 
remembered  that  portal  blood  is  very  different  from  the  proper  systemic 
blood,  and  that  there  are  many  changes,  beyond  all  question,  which  can 
take  place  with  rapidity  in  the  former,  but  which  do  not  take  place  in  the 
latter. 

Sugar,  whether  it  has  been  received  as  an  ingredient  of  the  food,  or 
arisen  from  the  metamorphosis  of  starch,  is,  as  we  have  said,  only  a  tem- 
porary form,  which  passes  quickly  onward  to  the  state  of  lactic  acid.  To 
this  we  must  impute  the  acid  reaction  which  is  observed  throughout  the 
length  of  the  small  intestine,  and  which  can  not  be  attributed  to  the  gas- 
tric juice,  a  reaction  occurring  in  spite  of  the  alkalinity  of  the  bile  and 
pancreatic  secretion.  This  pushing  of  the  carbohydrate  forward  to  the 
state  of  lactic  acid  is  very  generally  imputed  to  the  intestinal  juice,  which 
greatly  re-enforces  the  power  of  the  saliva  and  pancreatic  fluid;  some  have 
even  supposed  that  the  bile  aids  in  producing  this  effect.  Of  this,  how- 
ever, there  is  no  satisfactory  proof. 

From  the  experiments  of  Von  Becker,  who  injected  saccharine  solu- 
tions at  intervals  of  a  quarter  of  an  hour  into  the  stomach  of  rabbits,  it 
was  found  that  4.5  parts  of  sugar  were  absorbed  each  hour  for  every  1000 
parts  weight  of  the  animal.  Whatever  may  have  been  the  form  of  sugar 
administered,  as,  for  instance,  cane-sugar,  it  quickly  passes  into  the  con- 
dition of  glucose  in  the  intestine,  and  from  that  to  lactic  acid.  Thus  sug- 
ar of  milk  may  be  traced  in  an  hour  as  far  as  the  coecum,  communica- 
ting to  the  contents  of  the  small  intestine  an  intense  acid  reaction. 

Since  lactic  acid  discharges  very  important  offices  in  the  animal  econ-. 
omy,  it  may  be  worth  while  to  observe  its  properties,  and  productionand 
the  circumstances  under  which  it  is  produced.  Very  many  properties  of 
liquids  containing  organic  matter  yield  it  abundantly:  thus  it  '' 
is  found  in  sauer  kraut,  a  preparation  of  cabbage.  It  is,  however,  more 
conveniently  obtained  from  milk,  and  hence  the  term  lactic  acid.  The 
diluted  solution  obtained  from  this  source,  being  concentrated  by  evap- 
oration, furnishes  a  sirupy  liquid,  heavier  than  water,  having  an  intense- 
ly sour  taste,  a  great  affinity  for  water,  and  therefore  attracting  it  from 
the  air,  and  dissolving  freely  in  it.  With  metallic  oxides  it  forms  solu- 
ble salts,  and  in  the  concentrated  sirupy  state  has  the  remarkable  con- 


74  LACTIC   ACID. 

stitution  that  it  contains  six  atoms  of  each  of  its  elements,  carbon,  hy- 
drogen, and  oxygen. 

The  production  of  this  acid  in  organic  substances  is  very  common. 
It  depends  on  the  same  principle  as  presented  in  duodenal  digestion, 
which  it  therefore  very  strikingly  illustrates.  As  an  example  deserving 
of  attentive  consideration,  its  development  in  milk  may  be  offered. 

When  milk  is  exposed  to  the  air  it  eventually  turns  sour,  the  sour- 
ness being  due  to  the  appearance  of  lactic  acid.  In  its  sweet  state,  the 
milk  may  be  regarded  as  consisting  of  casein,  or  the  curdy  principle,  a 
substance  belonging  to  the  protein  group,  insoluble  in  pure  water,  but 
abundantly  soluble  if  a  little  free  or  carbonated  alkali  be  present ;  of  milk 
sugar,  dissolved,  and  of  butter  held  in  suspension  in  water.  The  ac- 
Production  of  ^on  ta^mS  P^ace  during  the  souring  is  as  follows :  Under 
lactic  acid  the  influence  of  atmospheric  oxygen,  which  for  this  purpose 
rom  milk.  must  liswQ  access,  the  nitrogenized  principle,  the  casein,  be- 
gins to  change,  and,  for  reasons  presently  to  be  more  particularly  exam- 
ined, impresses  a  change  on  the  sugar,  splitting  its  atom  so  as  to  give 
rise  to  the  production  of  lactic  acid.  As  this  forms,  it  renders  the  casein 
insoluble,  and  the  milk  begins  to  coagulate,  to  prevent  which  a  little  car- 
bonate of  soda  may  from  time  to  time  be  added.  All  the  sugar  origin- 
ally present  in  the  milk  is  soon  acidified,  but  a  much  stronger  solution 
can  be  made  by  adding  more  milk  sugar  as  the  process  of  exhaustion 
goes  on,  and  the  change  can  be  thus  kept  up  until  the  casein  itself  is 
quite  consumed. 

On  examining  this  process  critically,  we  observe  that  every  thing  de- 
pends on  the  change  occurring  in  the  nitrogenized  principle,  the  casein. 
This,  under  the  circumstances,  takes  on  an  incipient  oxidation,  and  com- 
pels the  sugar  atom  so  to  divide  as  to  give  rise  to  the  production  of  lac- 
tic acid.  This  ceases  the  moment  the  casein  ceases  to  change,  and  re- 
commences the  moment  the  casein  is  permitted  to  reoxidize.  The  de- 
struction taking  place  in  the  casein  is  propagated  to  the  sugar,  the 
physical  peculiarity  being  that  the  atom  of  sugar  is  merely  divided,  fis- 
sured, or  split,  and  gives  rise  to  the  production  of  lactic  acid,  and  no 
other  substance.  The  whole  process  is  therefore  essentially  one  of  sub- 
division, a  conclusion  which  should  be  carefully  borne  in  mind  in  apply- 
ing these  experimental  principles  to  the  physiological  function  of  diges- 
tion. So  far  as  the  result  is  concerned,  the  two  cases  are  the  same. 

Many  other  organic  liquids  furnish  similar  illustrations.  Thus,  in 
Production  of  ^e  °Peration  of  making  starch  for  commercial  purposes,  con- 
lactic  acid  siderable  quantities  of  that  substance  are  turned  into  lactic 
>m  starch.  &CQ  constituting  what  the  manufacturers  term  sour  liquor. 
Nor  is  it  even  requisite  that  so  much  water  should  be  present  as  to  give 
the  liquid  condition  ;  for  if  wheat  flour  be  made  into  a  paste,  and  kept  for 


LACTIC  ACID   IN   THE   SYSTEM.  75 

some  days  in  a  warm  place,  its  gluten  induces  such  a  change  that  the 
starcft  turns  into  lactic  acid,  and  the  paste  becomes  sour. 

Of  lactic  acid  there  are  two  kinds ;  that  derived,  as  hereafter  stated, 
from  muscle  juice,  is  the  alpha  lactic  acid,  and  that  from  the  Alpha  and  beta 
fermentation  of  sugar  the  beta  lactic  acid.  As  it  occurs  in  lactic  acid- 
the  gastric  juice,  associated  with  or  replacing  hydrochloric  acid,  it  is  of 
the  beta  variety.  Whatever  may  have  been  the  source  of  this  portion 
of  it,  whether  it  has  been  derived  by  gastric  secretion  or  through  the 
transmutation  of  amylaceous  food  by  the  saliva,  its  abundant  occurrence 
in  the  contents  of  both  the  small  and  large  intestines,  in  which  it  is  rec- 
ognized by  the  peculiarities  of  its  zinc  and  magnesia  salts,  confirm  the 
conclusion  that  in  this  case,  at  least,  the  beta  form  arises  from  the  opera- 
tion of  the  digestive  juices. 

Lactic  acid  undergoes  rapid  absorption  through  the  intestine,  and  is 
as  rapidly  disposed  of  in  the  system.  Thus  Lehmann  found,  after  tak- 
ing half  an  ounce  of  dry  lactate  of  soda,  that  in  thirteen  minutes  his 
urine  had  become  alkaline.  On  injecting  the  same  salt  into  the  jugular 
vein,  it  appeared  in  from  five  to  twelve  minutes  as  carbonate  of  soda  in 
the  urine. 

Berzelius  first  discovered  the  existence  of  lactic  acid  in  the  juice  of  the 
muscles.  Liebig  showed  that,  in  quantity,  there  is  more  pr0(juction  of 
present  in  this  source  than  is  sufficient  to  neutralize  the  alkali  lactic  acid  by 
of  all  the  other  liquids  or  juices  of  the  body.  Muscle  lac-  * 
tic  acid  is  removed  away  with  rapidity  by  the  lymphatics.  Berzelius 
concluded  that  its  quantity  increases  in  proportion  to  the  exercise  the 
muscle  has  undergone ;  and  this  would  lead  to  the  inference  that  it  is 
one  of  the  chief  products  of  muscular  waste ;  for  it  is  not  to  be  supposed 
that  its  appearance  in  muscle  juice  is  because  those  organs  attract  it 
from  the  blood,  in  which  it  pre-exists,  derived,  perhaps,  from  the  trans- 
formation of  amylaceous  substances  in  the  intestine,  for  the  muscles  of  the 
carnivora  yield  as  much  of  it  as  those  of  the  herbivora ;  and  though  it  can 
not  be  artificially  made  directly  from  albuminous  material,  yet  it  would 
seem  that,  with  urea  and  ammonia,  it  might  arise  from  the  breaking  up 
of  creatine.  From  glycerine  lactic  acid  may  be  also  developed.  When- 
ever an  excess  of  it  is  produced  in  the  system,  either  by  muscular  action, 
unusual  diet,  or  imperfect  oxidation  in  the  blood,  it  may  be  detected  in 
the  urine.  Under  ordinary  circumstances,  doubtless,  very  large  quanti- 
ties of  it  are  destroyed  in  the  circulation,  giving  rise  to  the  production  of 
carbonic  acid  and  water  with  a  disengagement  of  heat. 

We  can  not  here  fail  to  remark  how  the  process  of  comminuting  the 
food  is  carried  forward  to  such  an  extent  that  the  absorbent  These  digest- 
vessels  are  able  to  take  it  up.  The  action  first  begins,  as  has 
been  shown  in  detail,  by  cutting  and  crushing  implements,  ions. 


76  DIGESTION   OF  FAT. 

the  teeth,  and  when  these  have  carried  the  subdivision  as  far  as  mechanical 
means  can,  it  is  continued  by  chemical  agents.  Upon  these  principles, 
the  pancreatic  juice  divides  starch  into  lactic  acid  in  duodenal  digestion — 
a  product  which,  without  difficulty,  finds  its  way  at  once  into  the  system. 

Besides  starch  and  sugar,  there  is  another  group  of  bodies  belonging 
Digestion  of  to  the  class  of  calorifacient  food,  which,  in  the  case  of  carniv- 
fafc-  orous  animals,  seems  to  be  exclusively  employed.  The  fats 

and  oils  constitute  this  group. 

The  action  of  the  pancreatic  and  enteric  juices  upon  these  bodies,  in 
bringing  them  into  the  condition  of  an  emulsion,  has  already  been  stated. 
That  this  occurs  in  the  intestine  appears  from  the  fact  that  if  the  pan- 
creatic duct  be  tied,  no  emulsion  forms,  and  the  chyle  in  the  laeteals 
is  limpid  instead  of  being  milky.  In  the  rabbit  this  duct  opens  much 
lower  in  the  intestine  than  the  biliary,  and  it  is  observed  that  it  is  only 
after  the  food  has  passed  that  point  that  it  becomes  emulsioned.  The 
place  for  pancreatic  digestion  seems  to  be  very  constant  in  tribes  that  are 
far  apart  in  habits  of  life.  Thus,  in  fishes,  the  pancreas  consists  of  a  cor- 
onet of  coecal  tubes,  surrounding  the  pyloric  extremity  of  the  intestine, 
each  opening  into  that  organ  by  a  separate  mouth. 

The  fats  reach  the  duodenum  without  undergoing  any  change.  There, 
under  the  influence  of  the  pancreatic  juice,  they  become  subdivided  into 
extremely  minute  portions,  which,  absorbed  by  the  laeteals,  give  to  the 
chyle  its  characteristic  aspect.  Beyond  this  condition  of  subdivision 
no  other  change  is  thus  far  impressed,  the  fat  of  the  laeteals  being  abso- 
lutely the  same  as  that  of  the  chyme.  To  the  introduction  of  fat  into 
the  laeteals,  the  presence  of  bile  seems  to  be  necessary,  or,  if  not  absolute- 
ly necessary,  absorption  is  greatly  facilitated  by  it. 

The  gastric  and  pancreatic  juices  stand  in  a  remarkable  relation  to  one 
Bernard's  doc  ano^ner»  the  former  being  an  acid  liquid,  having  the  power 
trine  of  the  ef-  of  bringing  into  a  state  of  solution  nitrogenized  bodies,  such 
and  alkalinity  as  ^Tm  5  tne  latter  alkaline,  without  action  on  nitrogenized 
in  the  digest-  bodies,  but  operating  energetically  on  starch,  sugar,  and  oils. 

JU1<  From  this  it  might  be  supposed  that  the  intrinsic  qualities  of 

these  juices  are  different,  and  that  they  act  in  this  manner  because  of  a 
special  dissimilarity  of  constitution. 

Attempts  have  been  made  to  prove  that  this  difference  of  action  de- 
pends wholly  on  the  chemical  relations  of  the  juice  itself.  If  pancreatic 
juice  or  saliva  be  purposely  acidulated  with  hydrochloric  acid,  it  is  said 
that  it  loses  at  once  the  power  of  acting  on  calorifacient  food,  but  can 
bring  about  the  solution  of  the  histogenetic.  On  the  other  hand,  if  gas- 
tric juice  be  rendered  alkaline  by  admixture  with  soda,  it  no  longer  dis- 
solves fibrin  or  coagulated  albumen,  but  gains  the  power  of  acting  on 
starch  and  sugar.  Since,  then,  it  thus  appears  that  the  same  organic  body 


ORGANIC   PRINCIPLE   OF   DIGESTIVE  JUICES.  77 

becomes  endowed  with  one  or  other  of  these  properties,  according  as  it  is 
acidulated  or  alkalinized,  the  function  of  digestion  is  presented  to  us  un- 
der a  simple  aspect.  It  is  upon  these  principles  that  we  may  explain 
the  fact  that  the  presence  of  bile  in  the  stomach  suspends  or  arrests  the 
digestion  going  on  in  that  organ. 

Though  the  views  here  expressed  are  such  as  are  received  among  many 
chemists,  yet  it  is  still  open  for  consideration  whether  the  The  nature  of 
nature  of  the  result  which  is  reached  in  these  cases  does  not,  the  orsanic  in- 

.      gredient  more 

to  a  great  extent,  depend  upon  the  nature  of  the  organic  important  than 
changing  body,  the  ferment,  which  first  sets  up  the  action.  the  reaction- 
Many  circumstances  would  lead  us  to  infer  that  this  must  be  the  case, 
and  that,  as  with  differences  of  temperature,  so  also  with  these  differences, 
the  final  result  may  present  distinct  variations,  though  they  may  be  with- 
in a  certain  range  or  limit.  Thus,  though  the  saliva  and  pancreatic  juice 
are  both  alkaline,  and  both  impress  in  a  general  way  the  same  digestive 
change  on  starch  and  sugar,  a  minute  examination  of  the  results  of  their 
action  would  doubtless  lead  to  the  detection  of  shades  of  difference — va- 
riations which  could  only  be  attributed  to  the  difference  between  the  act- 
ive organic  principle  of  the  pancreatic  juice,  and  ptyaline,  the  correspond- 
ing principle  of  the  saliva. 

The  imputed  control  which  the  alkalinity  or  acidity  of  the  digesting 
juices  exerts  in  determining  the  result,  illustrates  the  import-  j>e]atj  n  f 
ant  function  discharged  by  common  salt,  which  furnishes  to  common  salt  in 
the  juices  of  the  stomach  and  intestine  the  characteristic  in-  dl£estlon- 
gredients  they  require  by  breaking  up  readily  into  hydrochloric  acid  and 
soda,  and  re-forming  at  once  whenever  these  materials  are  brought  in 
contact.  There  is,  therefore,  an  important  reason  for  the  instinct  which 
animals  display  in  resorting  to  the  use  of  this  substance,  as  in  the  buffa- 
lo licks  at  the  West,  and  the  necessity  which  men  experience  to  add  it 
as  a  condiment  to  their  food.  But  though,  by  furnishing  an  acid  or  al- 
kali, as  the  case  may  be,  it  determines  the  nature  of  the  work  which  the 
secreting  juices  perform,  it  is  not  to  be  regarded  as  the  prime  mover  of 
the  change.  It  guides  rather  than  works.  The  efficient  principle  bring- 
ing about  digestion  appears  always  to  be  a  nitrogenized  body,  acidulated, 
perhaps,  for  the  production  of  one  duty,  and  rendered  alkaline  for  the  per- 
formance of  another. 

Directing  our  attention  now  more  particularly  to  the  phenomena  dis- 
played by  such  a  changing  nitrogenized  principle,  the  folio  wing,  illustra- 
tions will  serve  to  show  that  there  is  nothing  mysterious  in  its  operation. 
Out  of  many  cases  which  might  be  selected,  those  now  to  ]be  offered  are 
more  particularly  interesting,  since  they  refer  to  substances  extensively 
used  in  the  diet  of  man. 

First,  of  wine.     A  grape,  if  perfectly  sound,  will  keep  for  a  consider- 


78  ILLUSTRATIONS   FROM  WINE  AND   BREAD. 


Illustration  a^e  length  °^  tmie  without  undergoing  any  change  ;  but  if 
from  the  mak-  a  puncture  be  made  in  it  to  give  the  air  access,  it  rapidly  de- 
ine'  teriorates.  The  precise  change  taking  place  is  perhaps  bet- 
ter understood  by  observations  on  the  expressed  juice  of  this  fruit.  If 
grapes  be  pressed  beneath  the  surface  of  quicksilver,  and  the  juice  be  col- 
lected in  an  inverted  jar,  without  ever  coming  in  contact  with  the  atmos- 
pheric air,  it  may  be  kept  for  a  long  time  without  any  apparent  change  ; 
but  if  a  small  quantity  of  air,  or  only  a  single  bubble  of  oxygen  is  per- 
mitted to  enter  the  jar,  and  the  temperature  is  that  of  a  summer's  day,  an 
intestine  commotion  or  fermentation  at  once  ensues,  carbonic  acid  escapes, 
alcohol  arises  in  the  liquid,  and  the  sugar  which  was  in  the  grape-juice 
disappears.  But  the  quantity  of  sugar  thus  capable  of  being  destroyed 
is  limited,  and  a  point  is  eventually  reached  at  which  no.  more  sugar  can 
be  decomposed,  and  no  more  carbonic  acid  set  free. 

The  juice  of  the  grape  contains  a  nitrogenized  principle  resembling  al- 
bumen. It  is  this  which  is  in  reality  the  active  body.  So  long  as  ox- 
ygen is  excluded,  this  nitrogenized  substance  remains  unaltered,  but  the 
moment  the  air  finds  access,  a  change  begins.  The  sugar  which  is  pres- 
ent in  the  juice  becomes  involved  in  the  movement  going  on,  which  is 
propagated  by  degrees  to  all  its  atoms,  dividing  each  into  two  well-known 
and  well-marked  bodies.  The  period  at  which  no  farther  change  takes 
place  in  portions  of  sugar  'which  may  have  been  purposely  added  is 
when  the  nitrogenized  principle  has  disappeared. 

Carbonic  acid  and  alcohol  are  the  two  substances  arising  in  this  de- 
composition. Their  mode  of  origin  is  obvious  when  it  is  understood 
that  one  atom  of  sugar  can  be  so  divided  as  to  yield  four  of  carbonic  acid 
and  two  of  alcohol.  In  this  artificial  instance,  the  subdivision  is  even 
more  complex  than  that  which  occurs  in  duodenal  digestion,  in  which  the 
sugar  atom  is  subdivided  into  two  equal  and  symmetrical  parts,  two 
atoms  of  lactic  acid.  In  the  following  formulas,  (1)  represents  the  case 
of  vinous  production,  (2)  that  of  duodenal  digestion  : 

(1)  .....  C12  H12  013=4  (C02)+2  (C4  H6  OJ. 

(2)  .....  C13H13013=2(C6H606). 

Second,  of  bread.  If,  in  the  preceding  case,  a  transmuting  nitrogen- 
T11  ized  body  breaks  the  sugar  atom  so  that  alcohol  is  one  of  the 

Illustration  J  ,.&..,        -,,. 

from  making  products,  and  upon  this  principle  all  wines  and  intoxicating 
bread.  liquors  are  made,  the  instance  now  presented  is  of  far  more 
interest  to  the  well-being  of  man.  The  use  of  wine  undoubtedly  adds 
not  only  to  social  enjoyment,  but  sometimes  conduces  to  health  —  a  ben- 
efit, alas  !  often  attended  with  a  thousand  ills.  Not  so  with  bread,  em- 
phatically and  truly  described  as  the  staff  of  life. 

The  making  of  wine  and  of  leavened  bread  are  two  of  the  oldest  chem- 


ILLUSTRATION   FROM  THE  MAKING   OF  BREAB.  79 

ical  processes.  Their  origin  is  lost  in  a  remote  antiquity,  and  so  uni- 
versally are  their  benefits  acknowledged  that  their  use  is  diffused  all  over 
the  world. 

Experience  proves  that  the  best  bread  is  made  from  fine  wheaten  flour, 
mixed  into  a  paste  with  a  due  proportion  of  water.  A  certain  quantity 
of  a  nitrogenized  substance  undergoing  incipient  oxidation,  termed  yeast, 
is  added,  and  the  whole  submitted  to  a  gentle  temperature.  All  flour 
contains  a  small  quantity  of  sugar ;  on  this  the  yeast  immediately  acts, 
dividing  it,  as  in  the  former  case,  into  carbonic  acid  and  alcohol.  If 
enough  sugar  is  not  present,  more  under  the  circumstances  is  formed  from 
starch.  The  acid  gas,  as  it  is  set  free,  can  not  extricate  itself  from  the 
surrounding  dough,  but  expands  into  a  thousand  little  vesicles  or  bub- 
bles, which  give  that  peculiar  porosity  for  which  this  kind  of  bread  is  so 
highly  prized.  At  this  period,  before  baking,  the  other  substance  which 
has  arisen  from  the  destruction  of  the  sugar — the  alcohol — is  contained 
in  the  dough,  and  is  expelled  therefrom  along  with  the  excess  of  water 
by  the  high  temperature  of  the  oven,  which  also,  by  increasing  the  expan- 
sion of  the  included  gas,  adds  to  the  porosity  of  the  bread.  In  some 
baking  establishments  arrangements  have  occasionally  been  made  to  con- 
dense the  alcohol  as  it  rises  from  the  bread.  The  good  and  evil  of  life 
are  often  closely  intermixed.  The  advocate  of  total  abstinence  from  al- 
cohol may  with  reason  look  upon  half-baked  bread  distrustfully.  The 
enemy  is  lying  in  ambush  for  him. 

On  some  occasions,  instead  of  using  yeast,  a  piece  of  leaven,  that  is, 
dough  in  a  state  of  incipient  putrefaction,  is  employed.  The  mode  of 
action  is,  however,  the  same.  The  use  of  this  material  well  illustrates 
the  progressive  nature  of  these  changes,  and  how  the  action  gradually 
passes  from  point  to  point  of  the  entire  mass.  It  is  written,  "A  little 
leaven  leaveneth  the  whole  lump." 

In  the  cases  here  presented  the  action  is  one  of  subdivision.  A  com- 
plex atom  has  its  constitution  broken  up,  and  is  separated  These  actions, 
into  distinct  parts.  When  such  a  change  is  once  commenced  ^^^are  dl~ 
in  a  mass,  there  is  a  liability  for  the  whole  to  become  in-  subdivisions, 
volved,  just  as,  when  we  ignite  one  point  in  a  pile  of  combustibles,  the 
fire  spreads  throughout ;  or  as,  when  on  one  part  of  a  piece  of  fresh  meat 
a  small  portion  in  a  putrescent  state  is  laid,  the  corruption,  with  measured 
rapidity,  proceeds  from  part  to  part,  until  the  whole  is  decayed.  One 
after  another,  the  particles  submit  in  succession. 

Over  all  these  subdividing  actions  heat  exerts  the  most  extraordinary 
influence,  so  that  for  a  given  effect  to  be  produced  it  is  abso-  influence  of 
lutely  necessary  that  a  given  temperature  should  be  main-  gubdMSng686 
tained.     Thus,  if  we  take  the  saccharine  juice  of  almost  any  actions, 
kind  of  fruit,  and  cause  it  to  be  acted  on  by  a  changing  nitrogenized  body, 


80  ^EFFECTS   OF   TEMPERATURE   ON   FERMENTS. 

it  will  yield,  as  just  stated,  alcohol  and  carbonic  -acid  so  long  as  the  tem- 
perature ranges  about  75° ;  but,  every  thing  remaining  the  same,  if 
the  temperature  be  raised  to  100°  or  120°,  neither  alcohol  nor  carbonic 
acid  is  formed,  but  in  their  stead  other  products  arise,  such  as  lactic  acid, 
gum,"  and  manna.  Though,  therefore,  decomposition  will  go  on  through- 
out all  this  range  of  temperature,  the  products  will  vary  very  much,  al- 
cohol being  formed  at  a  low,  and  lactic  acid  at  a  high  degree. 

Again,  the  decomposition  of  milk  furnishes  a  very  instructive  instance. 
When  the  temperature  ranges  from  50°  to  75°,  the  liquid  turns  sour, 
owing  to  the  formation  of  lactic  acid ;  but  if  the  temperature  is  over  90°, 
the  products  are  different,  for  now  a  true  vinous  fermentation  sets  in,  al- 
cohol and  carbonic  acid  appearing.  It  is  on  this  principle  that  the  Tar- 
tars make  an  intoxicating  liquid  from  mare's  milk.  The  fermentation  of 
milk,  therefore,  yields  lactic  acid  at  a  low,  and  alcohol  at  a  high  degree. 

On  comparing  these  illustrations,  the  results  stand  in  direct  contrast, 
but  both  show  the  great  influence  which  a  specific  degree  of  heat  exer- 
cises over  such  subdivisions ;  and,  as  a  consequence  of  this  principle, 
which  obtains  equally  in  the  physiological  case,  we  recognize  the  neqes- 
sity  of  maintaining  the  cavity  of  the  stomach  and  intestine  uniformly 
at  a  temperature  which  is  fixed,  otherwise  there  would  cease  to  be  any 
uniformity  in  the  subdivision  of  the  food,  occasioned  by  the  digestion 
there  going  on.  These  principles,  moreover,  lead  to  the  explanation  of 
the  action  of  such  stimulating  substances  as  alcoholic  liquids,-  pepper, 
etc.,  which  at  once  determine  a  local  elevation  of  temperature ;  they  also 
explain  the  injurious  effects  which  may  ensue  from  intemperate  draughts 
of  ice-cold  water. 

A  nitrogenized  substance,  in  a  state  of  change,  can  thus  bring  about  a 
definite  action  on  fibrin,  coagulated  albumen,  or  casein  in  the  stomach, 
or  on  starch  in  the  intestine,  so  long  as  a  temperature  of  100°  is  main- 
Loss  of  power  tained,  but  in  every  known  instance  this  transmuting  power 
l\t™tTmpe£  *s  tota%  destroyed  by  exposure  to  a  very  low  or  very  high 
ature.  degree  of  heat.  Large  masses  of  animal  matter — whole  car- 

casses— may  be  preserved  for  many  centuries  unchanged  if  the  tempera- 
ture is  kept  down  to  32°.  A  striking  example  of  this  occurs  in  the  case 
of  the  extinct  elephants  which  are  occasionally  thrown  on  the  shores  of 
the  Polar  Sea  from  icebergs,  in  which  they  have  been  entombed  for 
many  thousand  years,  their  flesh  remaining  in  a  perfectly  fresh  and  un- 
decayed  state.  And  as  respects  a  high  temperature,  an  exposure  to  212° 
totally  destroys  the  power.  On  this  principle,  all  kinds  of  meat  or  veg- 
etable substances  may  be  indefinitely  preserved.  If  such  are  inclosed  in 
metallic  canisters,  so  as  totally  to  exclude  the  atmospheric  air,  and  ex- 
posed to  a  bath  of  boiling  water,  they  may  then  be  carried  around  the 
world  without  undergoing  any  change. 


AETIFICIAL  PRODUCTION  OF  FAT.  81 

One  of  these  illustrative  cases  still  remains.  It  belongs  to  the  class 
of  changes  now  under  consideration,  and  deserves  a  prominent  examina- 
tion from  its  connection  with  duodenal  digestion.  It  is  the  production 
of  fatty  bodies  from  starch  and  sugar. 

Physiological  considerations  assure  us  that  there  are  circumstances 
under  which  oils  and  fats  can  be  formed  from  starch  and  production  of 
sugar  in  the  system.  Animals  can  be  fattened  by  feeding  fats  from  ear- 
on  potatoes,  or  other  such  food,  in  which  the  quantity  of  oil  °  y  rj 
is  quite  insignificant.  Bees  can  make  wax,  which  strictly  belongs  to  the 
group  of  fats,  though  they  are  fed  on  pure  white  sugar. 

Such  results  can  be  artificially  imitated.  If  a  strong  solution  of  sugar 
be  mixed  with  a  small  quantity  of  casein  and  powdered  chalk,  and  ex- 
posed to  a  temperature  of  more  than  80°,  carbonic  acid  and  hydrogen  are 
evolved,  and  butyric  acid  forms  as  the  butyrate  of  lime.  This  acid  sub- 
stance is  a  colorless  oily  liquid,  having  the  odor  of  rancid  butter,  in 
which  indeed  it  exists. 

From  a  review  of  all  the  preceding  facts,  we  may  conclude  that  a  nitro- 
genized  substance  secreted  by  the  follicles  of  the  stomach,  Contrast  of 
and  undergoing  incipient  oxidation,  acidulated  with  hydro- 
chloric  acid  obtained  by  the  decomposition  of  common  salt,  tion. 
or  with  lactic  acid  produced  by  a  continuation  of  salivary  digestion,  has 
the  power  of  dissolving  coagulated  albumen,  and  generally  those  articles 
of  food  which  belong  to  the  nitrogenized  class ;  that  -this  goes  on  in 
the  stomach,  it  being  the  function  of  that  organ  to  effect  the  digestion  of 
this  kind  of  food,  and  thereby  contribute  to  the  general  nutrition  of  the 
system.  The  muscular  tissues  are  supplied  from  this  source,  and  by  the 
stomach  their  waste  is  repaired. 

Another  and  distinct  digestion  takes  place  in  the  intestine,  commenc- 
ing immediately  after  the  food  gains  the  duodenum.  •  It  too  is  brought 
about  by  the  action  of  a  special  liquid,  a  mixture  of  the  pancreatic  and 
intestinal  juices.  The  chemical  reaction  of  this  juice  is  alkaline ;  in  this 
respect  it  is  therefore  antagonistic  to  the  gastric  juice.  This  quality  is 
due  to  the  soda  it  contains,  a  substance  derived  co-ordinately  with  hy- 
drochloric acid  from  the  decomposition  of  common  salt.  The  digestion 
of  starchy  and  saccharine  bodies  is  thus  effected  by  dividing  them  so  as 
to  produce  lactic  acid. 

This  done,  common  salt  is  reproduced  by  the  commingling  of  the  gas- 
tric, biliary,  and  pancreatic  products  together.  The  salt  is  carried  by  the 
absorbents  into  the  interior  of  the  system,  to  be  again  decomposed. 

Moreover,  the  pancreatic  and  enteric  juices  reduce  the  oleaginous  and 
fatty  bodies  to  the  condition  of  an  emulsion,  or,  if  they  be  not  present 
in  the  food,  give  origin  to  them  in  the  way  just  described.  • 

The  reaction  of  the  intestinal  contents  not  only  differs  in  different  por- 

F 


82  SALTS   AND   GASES   OF  THE   INTESTINE. 

Successive  tions  of  the  tube,  but  in  the  same  region,  in  different  parts 
tmSt^ouoi!  of  tne  mass' its  exterior  ma7  te  alkaline,  its  interior  acid,  or 
the  intestine,  the  converse.  The  acidity  which  has  been  imparted  by  the 
gastric  juice  seems  generally  to  have  disappeared  some  time  before  the 
large  intestine  is  reached.  In  this  an  alkaline  reaction  is  observed.  The 
causes  of  this  prolonged  acidity  are  very  various.  In  part  it  depends  on 
the  nature  of  the  food,  in  part  upon  the  gastric  juice,  as  has  just  been 
stated,  and  in  part  upon  the  production  of  lactic,  butyric,  and  other  acids. 
The  resinous  ingredients  of  the  bile  may  be  detected  as  far  as  the  lower 
extremity  of  the  ileum.  Glucose,  originating  in  the  action  of  the  pancre- 
atic and  intestinal  juices  on  starch,  may  be  recognized  throughout  the 
whole  length  of  the  canal,  but  that  which  has  been  introduced  in  the 
food  seems  to  be  absorbed  in  the  stomach  itself;  thus,  in  milk-fed  ani- 
mals, sugar  does  not  appear  to  descend  beyond  the  jejunum.  'The  trans- 
mutation and  reabsorption  of  biliary  matter  commences  in  the  small  in- 
testine and  proceeds  continuously,  so  that  by  the  time  the  middle  of  that 
portion  of  the  tube  is  reached,  half  the  bile  is  gone. 

Since  the  intestinal  absorbents  can  only  take  up  a  definite  proportion 
of  fat,  it  might  be  expected,  as  is  really  the  case,  that  after  an  unusually 
fatty  diet,  fat  substances  will  be  found  in  the  excrement.  Indeed,  a  cer- 
tain small  proportion  always  so  occurs. 

Of  the  salt  substances  usually  occurring  in  the  food,  most  disappear 
Salts  of  the  in-  during  their  passage  through  the  intestine,  and  hence  but  lit- 
testine.  tie  is  found  in  the  faeces ;  more  particularly  is  this  the  case 

with  those  of  a  very  soluble  kind.  Of  the  sulphates  and  chlorides  of  the 
food,  not  even  a  trace  may  occur  in  the  excrement.  If  these  substances 
should  not  be  required  for  the  uses  of  the  system,  they  are  promptly  re- 
moved by  the  kidneys,  and  in  the  same  manner  are  disposed  of  any  ab- 
normal salt  substances  which  may  have  been  purposely  administered,  as, 
for  instance,  iodide  of  potassium. 

The  gaseous  contents  of  the  intestine  originate  in  part  from  the  air 
Gases  of  the  that  has  been  introduced  during  the  mastication  of  the  food,  in 
intestine.  par£  fr0m  fermentative  processes  occurring  after  certain  articles 
have  been  used  which  are  only  imperfectly  digested,  and  in  part  from  the 
endosmosis  of  gas  from  the  blood  through  the  walls  of  the  intestinal  cap- 
illaries. As  compared  with  atmospheric  air,  though  the  composition 
must  necessarily  be  very  various,  the  intestinal  gas  shows  a  great  excess 
of  carbonic  acid  and  nitrogen,  a  diminution  and  sometimes  even  a  total 
absence  of  oxygen,  the  presence  of  pure  hydrogen,  and  of  its  carburets 
and  sulphurets.  The  quantity  of  this  latter  gas  is  less  than  might  be 
expected  from  its  odor,  and,  as  would  be  anticipated  from  the  circum- 
stances, the  accumulation  of  gas  is  much  more  abundant  in  the  large  than 
in  the  small  intestine. 


FORMATION  OF  F^CES.  83 

Schmidt  shows  that  the  intermediate  circulation  of  water  toward  the 
intestine  is  far  more  considerable  than  its  final  excretion,  and  Water  furnish- 
amounts  in  one  day  to  nearly  one  fourth  of  the  whole  quan-  |^0 1] 
tity  of  water  in  the  body. 

As  the  digested  mass  passes  onward,  driven  by  the  peristaltic  motions 
through  the  convolutions  of  the  intestine,  it  becomes  of  a  Complex  chan- 
more  solid  consistency,  as  the  absorbents  gradually  remove  testinai^on^" 
its  liquid  portions.  By  the  time  it  has  reached  the  coacum,  tents, 
the  same  effect  which  arose  in  the  stomach  from  salivary  digestion  is 
repeated,  for  the  traces  of  unabsorbed  lactic  acid  cause  nutritive  diges- 
tion to  be  again  feebly  resumed,  at  all  events  in  herbivorous  animals,  if 
not  in  man,  whose  ccecum  is  rudimentary,  under  the  form  of  the  appen- 
dix vermiformis.  From  Peyer's  glands  a  secretion  has  exuded,  which 
perhaps  gives  to  the  mass  the  characteristic  odor  it  is  now  assuming,  if, 
indeed,  these  organs  are  not  connected  with  absorption.  The  effete  re- 
mains are  finally  voided  as  fasces,  which,  due  allowance  being  made  for 
the  water  they  contain,  amounting  to  about  75  per  cent.,  may  be  rep- 
resented as  averaging  about  1J  ounce  per  day.  These  excrementitious 
remains,  colored  yellow  by  the  coloring  material  of  the  bile,  are  partly  de- 
rived from  the  residues  of  the  food  which  have  been  unacted  upon,  and 
partly  from  the  decay  of  the  system  itself.  The  microscopt  shows  the 
remains  of  cell  membranes,  and  the  walls  of  vegetable  vas-  Formation 
cular  tissues,  starch  granules,  and  chlorophyll,  the  relics  of  car-  of  faeces' 
tilaginous  and  fibrous  tissues,  shreds  of  muscular  fibre,  fat-cells.  From 
the  digestive  tract  there  have  been  derived  mucus  corpuscles,  epithelial 
cells,  and  the  coloring  matter  of  the  bile.  Perhaps,  too,  much  of  the  wa- 
ter which  gives  consistency  to  the  fasces  has  been  derived  from  the  intes- 
tinal walls,  for  in  quantity,  under  certain  circumstances,  it  may  exceed 
the  amount  that  has  been  used  as  drink. 

In  its  passage  through  the  intestine,  that  portion  of  the  bile  which  has 
not  been  absorbed  undergoes- considerable  changes,  its  conju-  Disappearance 
gated  acids  degenerating  into  dyslysin,  which  may  be  recog-  of  the  blle- 
nized  in  the  fseces,  as  is  also  the  case  with  the  modified  pigmentary  mat- 
ters ;  the  soluble  mineral  constituents  are,  for  the  most  part,  absorbed. 

The  reducing  agencies  in  the  intestine,  and  the  manner  in  which  sub- 
stances can  find  their  way  into  the  urinary  secretion,  is  well  Incidental  re- 
illustrated  by  the  administration  of  indigo,  which  undergoes  fnSntts?11 
deoxidation  into  the  condition  of  suboxide  of  isatine,  and  will,  tine, 
notwithstanding  the  agency  of  arterial  blood,  appear  in  that  condition  in 
the  urine,  to  which,  upon  contact  of  the  air,  it  imparts  a  blue  tint,  becom- 
ing more  intense  under  a  prolonged  exposure,  and  eventually  indigo-blue 
being  deposited.  Such  a  result  not  only  shows  how  energetic  are  the  re- 
ducing agencies  in  the  intestine,  but  also  with  what  facility  very  oxidiz- 


84  ABSOKPTION. 

able  material  may,  under  certain  conditions,  be  exposed  to  arterial  blood 
without  oxidation.  Yet  that  this  want  of  action  is  wholly  due  to  inci- 
dental circumstances  is  shown  from  the  fact  that  salts  of  organic  acids 
are  much  more  quickly  oxidized  in  the  blood  than  they  are  in  the  open 
air. 

It  is  interesting  thus  to  observe  how  the  death  of  one  part  of  the  body 
Advanta  e  mmisters  to  the  life  of  the  rest ;  for  the  nitrogenized  and  act- 
taken 'of  the  ive  principles  of  t!^  juices  secreted  for  the  accomplishment  of 
portion toor-  digestion  are  on  the  descending  career,  and  are  truly  dying 
ganize  an-  matter.  The  incipient  stage  of  decay  through  which  they  are 
passing  reacts  on  the  food,  and  prepares  it  in  a  temporary 
manner  to  replace  those  parts  of  the  body  which  are  ceasing  from  activ- 
ity, and  about  to  be  removed. 


CHAPTER  V. 

OF  ABSORPTION. 

Double  Mechanism  for  Absorption. —  The  Lacteals  and  Veins. — Lacteal  Absorption. — Descrip- 
tion of  a  Villus. —  Analogies  in  Plants.  —  Introduction  of  Fat  by  the  Villi.  —  The  Chyle. — 
Causes  of  the  Flow  of  Chyle. — Intermediate  Changes  on  its  Passage  to  the  Blood. — Action  of 
Peyer's  Bodies.  —  Lymphatic  Absorption.  —  Nature  of  Lymph.  —  Structure  of  the  Lymphatic 
System. —  Comparison  of  Chyle,  Lymph,  and  Serum. — Function  of  the  Lymphatic  System. — 
Production  of  Fibrin. —  Cutaneous  Absorption. —  Causes  of  the  Flow  of  Lymph. — Apparent  se- 
lecting power  of  the  Absorbents. —  Connection  of  the  Lacteals  and  Lymphatics  with  the  Locomo- 
tive and  Respiratory  Mechanism. 

THE  food,  after  digestion,  though  in  the  alimentary  tract,  is  exterior  to 
Double  mech-  ^e  anniial  system.  Means  have  therefore  to  be  resorted  to 
anism  for  ab-  for  its  introduction  into  the  circulation,  and  its  distribution 
to  every  part.  This  is  accomplished  by  a  double  mechanism, 
one  portion  of  which  is  adapted  to  the  digestion  which  has  been  going  on 
in  the  stomach,  the  other  to  that  which  is  completed  in  the  intestine. 
The  veins  which  are  profusely  spread  on  the  walls  of  the  digestive  cav- 
ity constitute  the  former  apparatus,  the  lacteal  vessels  the  latter. 

The  lacteal  vessels  may  be  described  as  delicate  tubes,  conveying  ma- 
Description  of  terials  absorbed  from  the  intestine  into  the  blood.  Their 
a  villas.  mode  of  origin  may  be  understood  by  considering  them  as 

projecting  with  a  fine  but  blunt  end  upon  the  inner  coat  of  the  intestine. 
This  projection  is  covered  over  with  smooth  muscle  cells  and  a  plexus  of 
blood-vessels,  a  continuation,  as  it  were,  of  those  of  the  mucous  coat  of 
the  intestine  itself;  they  are  held  together  by  connective  tissue,  and  over 
that  is  cast  a  covering  of  cylindric  epithelium.  This  construction  con- 


DISTRIBUTION   OF   BLOOD-VESSELS   TO   THE   VILLI. 


85 


stitutes  what  is  called  a  villus,  the  shape  of  which  is  conical,  or  perhaps 
cylindrical.  The  villus  may  then  be  regarded  as  a  process  of  mucous 
membrane. 

Fig.  23  is  a  section  of  the  wall  of  the  ileum, 
a  being  the  villi ;   b,  glands  of  Lie-  Structure  of 
berkuhn ;  <?,  muscular  layer  of  mu-  -the  intestinal 
cous  membrane ;  d,  follicles  of  a  Pey-  T 
er's  patch ;  0,  remainder  of  submucous  tissue  be- 
neath them;  y,  circular  muscles;  g  h,  longitu- 
dinal muscles.     (Kolliker.)  » 
fig.  24  represents  the  .distribution  of  blood- 
vessels to  the  villi  of  the  intestine  of  the  mon- 

Fvj.  24. 


Section  of  wall  of  ileum  magnified 
50  diameters. 


Distribution  of  arteries   and  veins  on  villi  of 
monkey. 


key.     The  figure  was  drawn  by  the  camera  lucida,  a  a  being  the  arteries, 
b  b  the  veins. 

The  form  of  the  villi  differs  in  different  regions  of  the  intestine.     In 
the  duodenum  thev  are  less  elevated,  laminated,  and  broad- 

t»      «-     ,  T  .    t     ••  •  •  T     -i      --i     Forms  of  villi. 

er,  Fig.  25.     In  the  jejunum,  more  projecting  or  cylmdroicl, 


Fig.  25. 


Fig.  20. 


Distribution  of  blood-vessels  on  the  villi  of  the 
duodenum. 


Distribution  of  blood-vctesels  on  the  villi  of  the  je- 
junum. 


Fig.  26.     In  all  cases,  however,  they  are  abundantly  supplied  with  blood- 


86  STRUCTURE    OF   THE   VILLI. 

vessels.  Their  epithelial  covering  of  cylindroid  cells  is  shown  in  the 
sectional  diagram,  Fig.  27,  a  a  ;  at  b  b  is  the  origin  of  the  lacteal  aris- 
ing obscurely.  '  Fig.  27. 

So  amply  are  the  villi  supplied 
with  blood-vessels,  that  if,  after  in- 
Various  opin-  jection  with  coloring 

materia1' their  cJlin- 

cells.  dric  epithelium  be  re- 

moved, they  seem  to  be  tinged  all 
over.  Each  cell  of  the  epithelium 
appears  to  be  filled  with  granular 
matter,  and  to  have  a  well-marked 

nucleus.        Some  anatomists  assert       Conical  villi  in  section,  with  cylindroid  epithelium. 

that  that  end  of  these  cells  nearest  the  cavity  of  the  intestine  is  in  reality 
open,  and  in  this  manner  they  account  for  the  ready  passage  of  oil  glob- 
ules into  them,  and  also  for  the  appearance  of  solid  foreign  bodies,  as  Os- 
terlein  observed. 

Though  we  have  described  the  lacteal  as  a  vessel  projecting  into  the 
Origin  of  the  interior  of  the  intestine,  it  is  by  some  viewed  rather  as  'a  mere 
lacteal.  excavation  in  the  villus.  The  villi  impart  to  the  mucous  mem- 

brane an  aspect  sometimes  likened  to  the  pile  of  velvet.  On  an  average, 
their  number  upon  a  square  inch  is  about  10,000.  The  entire  number 
of  these  organisms  must,  therefore,  amount  to  many  millions.  At  one 
time  it  was  supposed  that  the  lacteals  open  directly  into  the  intestine — an 
opinion  which  is  now  universally  abandoned.  The  action  of  each  villus  is 
doubtless  more  complicated  than  is  generally  represented,  for  the  organic 
fibre  cells  it  contains  give  to  it  the  power  of  executing  rhythmic  motions. 

When  the  operation  of  the  lacteal  vessels  as  absorbents  was  first  de- 
The  lacteals  tected,  it  was  believed  that  all  nutriment  is  introduced  by 

Sfc^anfef  t^ieir  means-  But  tnere  are  manj  animals  wholly  destitute 
absorption.  of  this  system  of  tubes,  for  instance,  the  invertebrates.  Even 
in  many  fishes  the  villi  are  absent.  In  such  cases  absorption  must  nec- 
essarily be  conducted  by  the  veins.  Moreover,  though  there  are  no  lac- 
teals on  the  walls  of  the  stomach,  nor,  indeed,  on  that  part  of  the  intes- 
tinal tube  which  is  higher  than  the  place  of  introduction  of  the  biliary 
and  pancreatic  ducts,  there  are  many  substances  freely  absorbed  from  the 
gastric  cavity  when  its  pyloric  orifice  is  tied.  It  has  already  been  men- 
tioned that  the  stomach  absorbs  water  with  remarkable  rapidity.  The 
doctrine  that  the  lacteals  are  the  exclusive  organs  of  absorption  must, 
therefore,  be  abandoned,  for  it  is  plain  that  the  venous  system  participates 
in  this  duty. 

The  function  of  absorption  has  therefore  to  be  examined  from  two 
points  of  view.  As  there  are  two  digestions,  one  producing  a  perfect  so- 


ABSORPTION   IN  PLANTS.  87 

lution,  and  the  other  an  emulsioned,  but  not  dissolved  state  Conditions  of 
of  the  food,  so  there  are  two  absorbent  systems,  the  lacteals 
and  the  veins.     The  lacteals  introduce  such  substances  as  are  tion. 
not  absolutely  dissolved,  particularly  the  oils  and  fats.     The  veins  ap- 
pear to  take  up  those  substances  only  which  are  completely  dissolved  in 
water. 

As  in  many  other  cases  in  physiology,  so  in  this,  a  correct  interpreta- 
tion of  the  functions  of  the  animal  mechanism  may  be  ob-  Abgor  tion  in 
tained  by  examining  the  corresponding  structures  and  func-^  plants,  their 
tions  in  plants.     In  the  more  perfect  of  these,  the  absorption  a 
of  watery  material  from  the  ground,  constituting  the  ascending  sap,  is 
brought  about  by  the  agency  of  collections  of  soft  cells,  which  are  placed 
at  the  extremity  of  each  rootlet.     They  are  designated  spongioles.     By 
their  action  the  fluid  is  forced  up  through  the  tubes  of  the  sap-wood  into 
the  leaves,  and  there  exposed  to  the  conjoint  agency  of  the  sun  and  air. 
A  change  is  thus  accomplished,  and,  from  being  crude,  it  turns  into  elab- 
orated sap,  and  now  descends  through  the  bark,  to  be  distributed  to  every 
part  of  the  plant.     Its  ascent  is  caused  by  the  cells  of  the  spongioles,  its 
descent  by  the  chemical  changes  occurring  among  the  cells  which  are 
found  in  the  structure  of  the  leaves. 

These  cells — both  of  the  roots  and  of  the  leaves — are  far  from  contin- 
uing their  action  for  an  unlimited  period  of  time.  At  the  most,  their 
existence  is  transient.  Those  of  the  roots  are  gradually  lost  by  decay, 
or  converted  into  solid  structure,  as  the  elongation  of  the  organs  through 
the  ground  goes  on.  Those  of  the  leaves  are  equally  transitory.  At 
periodic  intervals,  both  in  deciduous  and  evergreen  plants,  the  fall  of  the 
leaf  occurs — a  new  organism  succeeding  in  another  summer  to  make  up 
for  the  one  which  has  passed  away. 

Whatever  nutrient  material  is  taken  from  the  soil  in  the  case  of  plants 
is  introduced  by  the  aid  of  a  cellular  structure,  and  the  cells  die  after  ac- 
complishing their  duty. 

It  was  once  a  saying  among  physiologists  that  the  lacteals  are  the 
roots  of  animals,  and  in  this  there  is,  in  reality,  a  great  deal  Analogy  be- 
of  truth,  for  between  the  rootlet  of  a  plant  and  the  lacteal  of 
an  animal  there  is  a  conspicuous  relation,  not  only  in  struc-  roots, 
ture,  but  also  in  function.  As  is  seen  in  Fig.  27,  upon  each  villus  of 
the  intestinal  tube  there  is  a  layer  of  cylindric  cells,  underneath  which  the 
lacteal  vessel  takes  its  rise,  for  it  does  not  open  by  a  free  orifice  on  the 
interior  of  the  intestine,  but  its  flask-shaped,  loop-like,  or  convoluted  or- 
igin is  obscurely  seen  in  the  midst  of  the  cells.  The  aspect  which  the 
villi  present,  from  its  doubtful  nature,  has  led  to  the  erroneous  conclusion 
that,  as  soon  as  active  digestion  goes  forward,  cells  rapidly  develop  with- 
in the  epithelium,  and  continue  to  do  so  as  long  as  the  intestine  contains 


88  INTRODUCTION   OF   FAT. 

digested  matter ;  that  they  become  turgid  with  chyle,  and  have  a  diame- 
ter of  about  the  yJ^-  of  an  inch ;  that,  as  they  select  material,  they 
throw  it  into  the  lacteal  tube,  either  by  bursting  or  deliquescing,  and  at 
the  same  time  set  free  broods  of  germs  from  which  new  cells  are  developed. 
So  far,  therefore,  as  their  duration  is  concerned,  if  this  be  their  true  histo- 
ry, they  are  even  more  transitory  than  the  corresponding  cells  of  plants. 

That  the  lacteals  are  connected  with  respiratory  digestion  seems  to  be 
Fat  is  intro-  plainly  indicated  by  the  circumstances  of  their  occurrence, 
facteais  Into6  ^one  °^  them  are  found  upon  the  stomach,  nor  even  on  that 
the  blood.  part  of  the  duodenum  which  is  above  the  entrance  of  the  he- 
patic and  pancreatic  ducts,  but  below  that  point  they  are  scattered  in  pro- 
fusion all  over  the  small  intestine.  The  digestion  of  fatty  bodies  not 
taking  place  until  the  food  has  gained  the  duodenum,  vessels  for  the  ab- 
sorption of  the  emulsions  to  which  that  digestion  gives  rise  are  not  re- 
quired until  after  that  point  is  passed.  Correctly  speaking,  however, 
the  lacteals  are  only  lymphatics  which  are  taking  up  oil  presented  to 
them.  In  view  of  the  use  which  the  oils  subserve  in  the  animal  economy, 
the  lacteals  are  in  reality  an  appendix  to  the  respiratory  system.  There 
can  be  no  doubt  that  through  their  channel  oils  and  fats,  under  the  form  of 
emulsions,  are  transmitted  to  the  blood.  The  analysis  of  the  chyle  shows 
that  it  is  always  rich  in  fat,  and,  indeed,  it  is  supposed  by  some  physi- 
ologists that  the  objects  just  described. as  cells,  surrounding  the  origin  of 
the  lacteals,  are  nothing  more  than  oil  or  fat  globules  accumulated  there 
and  waiting  to  be  taken  up,  or  that  the  disappearance  and  exuviation  of 
the  so-called  cells  is  an  optical  deception,  due  to  their  walls  becoming 
permeated  with  oil. 

The  manner  in  which  oil  globules  collect  round  the  villus  I  have  re- 
marked as  being  very  strikingly  displayed 
in  the  case  of  the  gray  squirrel  after  feed- 
ing on  fatty  nuts.  As  shown  in  Fig.  28, 
the  whole  structure  looks  as  if  it  were  dis- 
tended with  oil  globules,  a  a,  in  the  midst 
of  which  the  origin  of  the  lacteal,  b  b  b,  may 
be  doubtfully  and  dimly  discerned. 

Although  it  can  not  be  admitted  that  the 
Evolution  and   production   and   deliquescence 

function  of  the       /•  .1  n        c     MV   •  i  Half-diagram  of  villi  of  the  gray  squirrel 

cells  of  the  °*  "ie  Ce-"S  °*  ^""  1S  a  demon-  after  feeding  on  nuts. 

villi.  strated  fact,  and  that  on  this  the  action  of  the  lacteals  as  ab- 

sorbent vessels  for  the  most  part  depends,  the  rapid  evolution  and  disap- 
pearance of  these  cells  is  by  no  means  a  physiological  impossibility.  Bot- 
anists assert  that,  in  a  single  night,  the  Bo  vista  giganteum,  a  puff-ball, 
can  develop  from  a  mere  point  to  such  a  size  that  it  must  contain  fifty 
thousand  millions  of  cells — a  number  that  seems  almost  incredible.  The 


THE   MESENTERIC  GLANDS.  89 

development  of  cells  in  the  villi  of  the  intestinal  tube,  in  countless 
crowds,  may  therefore  be  within  the  bounds  of  possibility. 

If  this  be  the  case,  the  cells  which  thus  come  rapidly  into  existence 
in  the  villi  appropriate  those  articles  of  respiratory  food  which  are  of 
imperfect  solubility  in  water.  To  this  class  the  oils  belong.  Each  cell 
then,  as  it  dies,  yields  up  its  contents  to  the  lacteal  tube.  In  the  white 
fluid,  the  chyle,  which  flows  along  those  tubes,  are  many  pale  or  color- 
less corpuscles  continually  coming  into  existence.  These  seem  to  im- 
press a  change  upon  the  chyle,  and,  to  give  a  full  opportunity  for  such 
action,  that  fluid  is  compelled  to  flow  gradually  through  long  and  sinuous 
channels,  for  the  glands  in  the  mesentery  may  be  regarded  as  convoluted 
windings,  or  rather  plexuses  of  tubes,  to  which  that  particular  form  is 
given  for  the  sake  of  closeness  of  package.  From  the  enveloping  cap- 
sule of  fibrous  tissue  of  the  glands  thin  sheets  are  projected,  Structure  of 
and  so  internetted  as  to  divide  the  whole  gland  into  many  the  mesenteric 
alveoli.  These  are  filled  with  a  pulpy  material  supplied  s  ar 
with  delicate  blood-vessels.  The  chyle  either  oozing  through  this  ma- 
terial eventually  escapes  from  the  gland  by  the  efferent  vessels,  or  makes 
the  passage  in  its  own  thin  tube.  In  reptiles,  in  which  there  are  no 
such  glands,  the  lacteals  are  extended  to  a  very  great  length. 

The  manner  in  which  the  chyle  passes  through  the  mesenteric  glands 
is  therefore  explained  differently,  according  to  the  view  Modeofaction 
which  is  taken  of  the  structure  of  those  organs.  If  they  ofthemesentc- 
are  considered  as  mere  dilatations  of  the  lacteal  vessel,  from  nc  s  al 
the  sides  of  which  partition  processes  are  sent  off,  the  interspaces  being 
filled  with  granular  material,  through  which  delicate  blood-vessels  pass, 
the  chyle  is  to  be  considered  as  oozing  through  this  granular  structure, 
and  crossing  directly  in  contact  with  it.  But  if  we  accept  the  doctrine 
that  the  chyle  is  conducted  through  the  gland  in  a  plexus  arising  from 
the  incoming  lacteal,  the  granular  material  being  outside,  then  the  influ- 
ence of  that  material,  in  whatever  it  may  consist,  takes  effect  through 
the  delicate  walls  of  the  plexus.  The  like  remarks  apply  to  the  lym- 
phatic glands.  Physically,  however,  the  condition  in  both  cases  is  the 
.same ;  the  incoming  liquid  is  simultaneously  exposed  in  the  gland  to 
the  influence  of  the  granular  pulp  and  to  arterial  blood. 

The  chyle,  delivered  into  the  lacteal  tube,  is  propelled  by  the  conjoint 
action  of  several  different  forces.     The  constant  accumulation  Causes  of  lhe 
of  liquid  at  the  origin  of  the  vessel  produces  a  pressure  which  flow  of  the 
can  only  be  relieved  by  motion  through  the  tube,  and  at  the  chyle' 
mouth,  where  the  lacteal  empties  into  a  vein,  as  sooner  or  later  all  do, 
either  directly  or  through  the  intervention  of  the  thoracic  duct,  a  suction 
force  is  exerted  on  the  contents  of  the  lacteal  by  the  passing  current  of 
the  venous  blood,  upon  the  well-known  hydraulic  principle  of  Yenturi, 


90 


MOTION   OF   THE   CHYLE. 


blood-vessels. 


that  if  into  a  tube,  a  b,Fig.  29,  through  which  a  current  of  water  is  stead- 

ily  flowing,  another  tube,  c  d,  opens,  its 
more  distant  end  being  in  communication 
with  a  reservoir  of  water,  e,  through  this 
tube  a  current  will  likewise  be  establish- 
ed, and  the  reservoir  be  emptied  of  its 
contents.  The  effect  is  still  greater,  as 
Bernouilli  demonstrated,  when  the  main 
current  is  flowing  toward  the  wide  end 
of  a  conical  pipe.  Moreover,  the  lacteal 
tubes  are  elastic,  and  furnished  with  valves, 
which  open  to  let  the  fluid  pass  toward 
the  veins,  but  close  in  the  opposite  way. 

Principle  of  venturi.  This  valvular  mechanism  renders  available 

any  pressure  arising  either  from  the  contractility  of  the  vessels  them- 
Mechanism  for  selves,  or  from  those  various  muscular  movements,  respira- 
transfemng  torv  or  voluntary*  which  affect  the  abdominal  walls.  The 

chyle  from  the          J  ,  .  f       • 

viiius  to  the  manner  of  introduction  of  the  great  lacteal  trunk — the  tho- 
racic duct — at  the  angle  of  junction  of  the  left  subclavian  and 
f.  DO.  jugular  veins,  is  also  very  felicitous,  for  the  suc- 

tion force  of  those  large  vessels  is  there  conjoin- 
ed, and  the  effect  is  at  a  maximum.  The  con- 
trol of  the  blood  motion  on  the  chyle  motion  is 
obvious  from  this,  that  as  soon  as  the  circula- 
tion stops  the  chyle  stops,  and  this  not  so  much 
from  the  engorgement  of  the  venous  trunks, 
which  renders  it  difficult  for  the  chyle  to  make 
its  way  into  them,  as  from  the  cessation  of  that 
tractile  force,  which  solicits  the  chyle  to  move 
into  the  blood. 

Fig.  30  represents  the  position  and  course  of 
the  thoracic  duct,  and  its  manner  of  introduction 
of  the  chyle  into  the  blood  circulation.  (Wil- 
son.) 

1,  Arch  of  aorta ;  2,  thoracic  aorta ;  3,  abdom- 
inal aorta ;  4,  arteria  innominata,  dividing  into 
right  carotid  and  right  subclavian  arteries ;  5, 
left  carotid ;  6,  left  subclavian ;  7,  superior  cava, 
formed  by  the  junction  of,  8,  the  two  vena?  in- 
nominata?, and  these*  by  the  junction,  9,  of  the  in- 
ternal jugular  and  subclavian  on  each  side ;  10, 
the  greater  vena  azygos  ;  11,  the  termination  of 
The  thoracic  duct.  the  lesser  in  the  greater  vena  azygos  ;  12,  recep- 


INTRODUCTION  OF  FAT.  91 

taculum  chyli,  several  lymphatic  trunks  opening  into  it ;  13,  the  thoracic 
duct,  dividing  opposite  the  middle  of  the  dorsal  vertebra?  into  two  branch- 
es, which  soon  reunite ;  the  course  of  the  duct  behind  the  arch  of  the 
aorta  and  left  subclavian  artery  is  shown  by  a  dotted  line ;  14,  the  duct, 
making  its  turn  at  the  root  of  the  neck,  and  receiving  several  lymphatic 
trunks  previously  to  terminating  in  the  posterior  aspect  of  the  junction 
of  the  internal  jugular  and  subclavian  vein ;  15,  the  termination  of  the 
trunk  of  the  ductus  lymphaticus  dexter. 

As  to  the  manner  in  which  digested  fat  finds  its  way  into  the  lacteals, 
it  seems  to  be  as  follows:  In  the  interior  of  the  epithelial  Mannerofthe 
cells  oil-drops  are  detected,  while  on  the  outer  part  the  sur-  introduction  of 
face  presents  a  pearly  aspect,  from  other  portions  of  oil  wait-  fat' 
ing  to  enter.  By  degrees,  all  the  cells  upon  the  exterior  of  the  villus  ex- 
hibit the  same  appearance,  the  particles  gradually  finding  their  way 
through  the  parenchyma  of  the  villus,  and  so  entering  the  lacteal  tube. 
If,  with  some  anatomists,  we  regard  the  lacteal  at  its  origin  as  not  being 
a  true  vessel,  but  only  an  excavation  in  that  parenchyma,  much  of  the 
obscurity  which  surrounds  the  explanation  of  the  manner  of  the  entry 
of  oleaginous  material  into  the  lacteal  is  removed.  If,  moreover,  with 
other  anatomists,  we  represent  the  intestinal  end  of  the  cylindric  cells  to 
be  wanting,  and  the  cells  themselves  to  be  truly  cup-shaped  forms,  filled 
with  a  peculiar  secretion,  through  which  fat  particles  and  even  solid  sub- 
stances may  pierce  their  way,  this  likewise  would  remove  much  of  the 
difficulty.  But,  after  all,  even  if  the  general  opinion  of  the  structure  of 
a  villus  is  adopted,  that  the  lacteal  commences  with  a  blind  pouch  or 
blunt  tube  surrounded  by  a  network  of  blood-vessels,  and  over  this  an 
epithelium  cast,  there  being  no  mouths,  or  pores,  or  apertures  of  discov- 
erable size  leading  into  the  lacteal  through  its  own  wall  and  enveloping 
structures,  we  should  also  remember  the  extreme  minuteness  of  the  oily 
particles  suspended  in  the  chyle,  and  still  more  particularly  that  even 
this  size,  small  as  it  is,  is  deceptive  ;  for,  in  passing  through  interstices 
too  minute  to  be  seen  even  by  optical  aid,  the  oil  particles  may  be  press- 
ed out  into  long,  thread-like  forms,  which,  as  soon  as  they  escape  into  the 
free  cavity  of  the  lacteal,  assume  the  spheroidal  appearance  by  reason  of 
their  own  cohesion,  just  as  a  blood-cell  can  pass  through  a  vessel  of  a 
diameter  far  less  than  its  own  by  lengthening  itself  out  into  a  linear 
shape,  and  reassuming  its  original  figure  as  soon  as  it  escapes  from  con- 
finement and  pressure.  Though,  therefore,  the  lacteals  commence  upon 
the  intestinal  walls  as  closed  tubes,  this,  in  reality,  offers  no  obstacle  to 
their  absorbing  power  when  their  molecular  porosity  is  considered. 

Perhaps  this  infiltration  or  intrusion  of  oily  material  is,  to  a  consid- 
erable extent,  aided  by  the  presence  of  the  bile,  or,  rather,  its  oily  con- 
stituent. It  is  capable  of  easy  demonstration  that  oil  will  rise  much 


92 


CHANGES   OF   THE   CHYLE. 


higher  in  a  capillary  glass  tube,  the  inside  of  which  has  been  coated  over 
with  bile,  than  in  the  one  which  has  not  been  so  prepared. 

The  liquid  which  has  been  gathered  into  the  lacteals  from  the  intes- 
tine pursues  its  course  to  the  veins,  and  ultimately  enters  them.  The 
special  changes  which  are  impressed  on  it  during  this  passage  will  new 
be  explained. 

The  constitution  of  the  chyle  varies  with  the  physiological  conditions 
Constitution  °^  ^e  S7stem-  After  a  period  of  fasting  it  is  colorless,  and 
and  changes  in  presents  the  general  aspect  of  lymph,  hereafter  to  be  de- 
scribed, but  during  digestion  it  is  a  whitish  milky  fluid, 
whence  its  name.  This  milkiness  depends  on  the  suspension  of  minute 
fat  or  oil  globules  in  it.  Their  diameter  is  commonly  stated  at  the 
"3  ToTo  of  an  inch.  Of  course,  the  composition  of  the  chyle  varies  in  dif- 
ferent animals,  and  even  in  the  same  animal  under  different  diets. 

Composition  of  Clujlc, 


Horse. 

Ass. 

Cat. 

Man. 

Water   

935.00 

902.37 

905.70 

904.80 

Fat 

15.00 

36.01 

32.70 

9  20 

Fibrin  

.75 

3.70 

1.30 

) 

Albumen          .  . 

35.00 

35.16 

>      70.80 

Extractive  

6.25 

15.65 

48.90 

10.80 

Salts 

8.00 

7.11 

11.40 

4  40 

1000.00 

1000.00 

1000.00 

1000.00 

With  so  many  causes  of  variation,  such  a  table  as  the  preceding  is 
only  valuable  as  giving  a  general  idea  of  the  nature  of  the  chyle.  We 
learn  from  it  that  the  predominating  solid  constituents  are  fat  and  albtK 
men.  The  percentage  amount  of  the  first  of  these  in  the  sample  of  hu- 
man chyle  is  very  low,  a  fact  due  to  the  circumstance  that  the  subject 
from  which  it  was  obtained — an  executed  criminal — had  eaten  but  little 
for  some  time  before  his  death.  In  like  manner,  the  chyle  of  horses 
which  have  been  kept  without  food  has  been  observed  to  exhibit  a  dim-' 
inution  of  its  fat  to  such  an  extent  as  to  be  less  than  one  tenth  of  the 
normal  amount.  It  is  to  be  remarked  that  the  saline  ingredients  of  the 
chyle  closely  represent  those  of  the  blood,  both  in  constitution  and 
amount. 

The  composition  of  the  chyle  varies  at  different  points  on  its  passage 
Constitution  of  to  the  veins,  there  being  a  gradual  diminution  of  the  albu- 
chyie  at  vari-  men  an(j  an  jncrease  Of  the  fibrin.  After  the  passage  through 
its  course.  the  mesenteric  glands  it  becomes  capable  of  coagulation, 
and  will  separate  into  a  serum  and  a  clot.  Examined  near  the  villi,  it 
may  be  regarded  as  ah  albuminous  liquid,  in  which  are  suspended  glob- 
ules of  fat  of  various  sizes,  down  to  the  degree  of  minuteness  just  speci- 
fied. The  nature  of  these  globules  is  determined  by  the  action  of  sul- 
phuric ether,  which  readily  dissolves  them.  After  passing  through  the 


CHANGES   IN  THE   CHYLE. 


93 


mesenteric  glands,  the  percentage  amount  of  albumen  declines,  and  the 
fat  globules  diminish  in  number.  Simultaneously  the  special  cells,  to 
which  the  name  of  chyle  corpuscles  is  given,  make  their  appearance,  and 
the  liquid  is  now  capable  .of  coagulating,  owing  to  the  production  of 
fibrin.  These  characters  become  more  strikingly  developed  as  the  chyle 
advances  in  the  thoracic  duct.  The  chyle  corpuscles  are  eventually  de- 
veloped into  red  blood-cells. 

.It  should  be  borne  in  mind,  in  all  discussions  respecting  the  composi- 
tion of  chyle  in  different  parts  of  its  course,  that  it  must  re-  ,, . 

r  -,11  It  is  affected  by 

ceive  transuded  matters  from  the  blood,  and  that  this  must  transudation 
more  particularly  occur  on  its  passage  through  the  mesen-  fromtheblood- 
teric  glands.  Owing  to  this,  it  is  quite  probable  that,  even  though  there 
should  be  an  actual  consumption  of  albumen  in  accomplishing  the  meta- 
morphoses which  are  taking  place,  the  apparent  percentage  amount  of 
that  ingredient  may  increase  by  transudation  from  the  blood.  It  ap- 
pears to  me  quite  probable  that  the  albuminous  material  in  the  lacteal,  at 
its  very  origin  in  the  villus,  has  been  derived  to  quite  as  great  an  extent 
by  transudation  from  the  plexus  of  blood-vessels  as  by  absorption  from 
the  digested  food. 

Whatever  may  be  the  special  manner  by  which  the  fats  pass  from  the 
intestine  into  the  lacteals,  they  have  scarcely  gained  those  saponificatiou 
vessels  before  they  undergo  a  change.     The  quantity  of  free  of  the  fat- 
fat  diminishes,  and  that  of  saponified  fat  increases ;  this  is  probably  ac- 
complished by  soda  obtained  from  the  blood.  * 

As  to  the  fibrin,  it  can  scarcely  be  supposed  that  the  imperfectly  co- 
agulable  variety  which  the  chyle  contains  should  have  been  Difference  be- 
derived  by  transudation  through  the  vessels  of  the  strongly  ^^^^~ 
contractile  kind  contained  in  the  blood ;  and,  in  view  of  all  chyle-fibrin, 
the  circumstances  of  the  case,  it  would  appear  that  the  explanation  we  shall 

offer  of  its  direct  origination  from  the 
chyle  albumen  by  oxidation  is  correct. 
The  chyle  corpuscles   are  readily 
distinguished  from  the  blood-  _. 

Nature  of 

cells,  not  only  by  their  white  chyle  cor- 
appearance,  but  also  by  their  actTo^^ 
form.     They  are  spheroidal,  reagentson 
and  either  homogeneous  or 
granular.     Those  of  the  frog  are  seen 
in  Fig.  31,  at  a  a,  sparsely  scattered 
among  the  elliptical  blood-cells.     The 
photograph  from  which  the  engraving  is 
taken  exhibits  nearly  the  average  pro- 

Chyle  corpuscles  with  blood -cells,  magnified  250  ,.  ,,    ,  -,      ,. 

portion  of  these  bodies  in  that  animal. 


diameters. 


94 


CHYLE   COKPUSCLES. 


By  the  action  of  water,  the  nucleus  of  the  chyle-cell  becomes  more  dis- 
tinct, its  increased  granular  aspect  making  it  more  visible,  as  in  Fig.  32. 

Fig.  32.  Fig.  33. 


Chyle  corpuscles  with  water,  magnif  ed 
500  diameters. 


Chyle  corpuscles  with  acetic  acid,  mag- 
nified 500  diameters. 


tern. 


By  acetic  acid  the  nucleus  is  greatly  contracted,  as  in  Fig.  33,  and  some- 
times even  escapes  from  the  cell. 

In  embryonic  life,  the  first  appearance  of  chyle  corpuscles  commonly 
coincides  with  a  change  in  the  arrangement  of  the  respiratory  mechan* 
ism,  as  the  closing  of  the  branchial  fissures,  indicating  a  connection  be- 
tween their  production  and  the  activity  of  interstitial  oxidation. 

It  has  been  previously  stated  that  the  bodies  known  as  Peyer's  glands 
Fever's  bodies  are  to  be  regarded  as  belonging  to  the  absorbent  rather  than 
^ie  Digestive  apparatus.  In  structure  they  are  analogous  to 
the  lymphatic  and  lacteal  glands,  consisting  of  a  capsule 
containing  granular  material,  in  which  loops  of  capillary  blood-vessels 
are  laid.  From  these  proceed  many  lacteal  vessels,  as  may  be  very 
plainly  observed  during  digestion.  Their  functions  would  therefore  seem 
to  be  the  submitting  of  the  chyle  to  the  simultaneous  influence  of  the 
blood  brought  by  the  arterial  capillaries,  and  the  pulpy  material  or  gran- 
ular plasma  they  contain.  They  are,  in  reality,  dilatations  of  the  absorb- 
ent vessels,  accomplishing  in  a  small  space  a  result  which  would  other- 
wise demand  a  very  long  lacteal  tube,  and  probably  not  impressing  any 
other  change  on  the  chyle  than  that  which  would  have  occurred  in  such 
a  tube,  if  of  sufficient  length. 

It  is  not  possible  clearly  to  understand  the  functions  of  the  lacteals 
.  without  a  description  of  the  structure  and  functions  of  the 

Structure  and  r 

functions  of  the  lymphatics,  for  these  vessels  conspire  in  their  action. 

tlcs*  Anatomical,  chemical,  and   physiological   considerations 

lead  us  to  conclude  that  the  formation  of  the  LYMPHATIC  SYSTEM  is 
closely  allied  to  that  of  the  LACTEAL.  The  two  classes  of  vessels  make 
their  appearance  together  in  fishes ;  the  lymphatics  originate  in  a  net- 
work of  delicate  tubes,  but  are  disseminated  through  all  the  soft  tissues 
except  the  nervous,  and  are  found  especially  in  the  skin.  The  fine  ini- 


PROPERTIES   OF  LYMPH. 


95 


tial  tubes  gradually  coalesce,  producing  those  that  are  of  a  larger  diame- 
ter, and  these  pass  through  glands,  which  might  indeed  be  regarded  as 
mere  plexuses,  and  eventually  empty  into  the  veins. 

A  few  minutes  after  if  has  been  drawn,  the  lymph  coagulates  into  a 
colorless  clot,  and  then  exhibits  contraction.  Compared  with  properties  of 
blood  in  like  circumstances,  the  clot  of  lymph  is  small  in  re-  iymph- 
lation  to  the  serous  portion.  In  other  respects  there  is  a  general  resem- 
blance between  lymph  and  blood  free  from  its  red  cells,  the  fibrin  and 
the  albumen  being  apparently  the  same  in  the  two  cases*  The  saline 
constituents  are  not  only  the  same,  but  bear  the  same  ratio  to  one  an- 
other in  the  two  fluids.  Their  absolute  percentage  amount  differs,  be- 
cause the  lymph  contains  a  larger  proportion  of  water  than  the  blood. 

The  lymph  arising,  as  we  shall  find,  by  transudation  from  the  capil- 
laries, must  obviously  vary  in  different  parts,  those  parts  taking  from 
the  blood  the  materials  they  require  for  their  nutrition,  and  yielding  to 
it  the  products  that  have  arisen  during  their  waste.  Whatever  in  this 
manner  changes  the  composition  of  the  blood,  must  also  occasion  a  change 
in  the  transuded  liquid.  Thus  Schmidt  has  shown  that  protein  bodies 
transude  through  the  capillaries  of  the  pleura  most  copiously ;  through 
those  of  the  peritoneum  not  to  half  that  amount ;  through  those  of  the 
brain  and  those  of  the  subcutaneous  areolar  tissue  to  a  less  and  less  ex- 
tent. Not  only  must  the  material  thus  oozing  from  the  capillaries  vary  in 
different  regions,  because  of  variations  in  the  mechanical  constitution  of 

ose  vessels,  but  it  must  also  change  even  in  the  same  locality,  through 
temporary  accidents,  such  as  changes  in  the  velocity  with  which  the  blood 
is  flowing.  An  attempt  has  been  made  to  show  that  the  transudation  will 
be  richest  in  albumen  as  the  blood  current  in  the  capillaries  is  slower. 

When  the  contents  of  the  lymphatic  vessels  are  submitted  to  analysis, 
and  compared  with  the  chyle,  a  striking  difference  is  appar-  composition  of 
ent.  The  chyle  contains,  as  has  been  already  stated,  large  brmPh- 
but  variable  proportions  of  fat  or  oil  in  an  extremely  subdivided  state, 
from  which  the  lymph  is  free.  The  leading  solid  constituent  of  the 
lymph  is  albumen,  and  this  indicates  the  use  of  the  system. 

Composition  of  Lymph. 


Horse. 

Ass. 

Man. 

Water  

950  00 

965  36 

961  00 

Fat  

.09 

Fibrin  

) 

1  20 

2  50 

Albumen  

J-        39.11 

1200 

27  50 

Extractive  

4  88 

15  59 

6  90 

Salts 

5  92 

5  85 

2  10 

1000.00 

1000.00 

1000.00 

The  functional  connection  between  the  lacteals  and  lymph  vessels  is 
very  well  illustrated  by  the  following  analysis,  which  ex-  Fasting  chyle 
hibits  the  composition  of  chyle  obtained  from  the  thoracic 


96  COMPAEISON   OF   LYMPH,  CHYLE,  AND   SERUM. 

duct  of  a  man  who  died  from  softening  of  the  brain,  and  who  took  noth- 
ing but  a  little  water  for  30  hours  preceding  his  death.     (L'Heritier.) 

Composition  of  CJiyle  after  Fasting. 

Water ,...  924.3G 

Fat  5.10 

Fibrin 3.20 

Albumen 60.02 

Salts 7.32 

1000.00 

The  constitution  of  the  chyle  so  nearly  approaches  that  of  the  lymph, 
Comparison  of  ^iat  we  aie  autnorize^  to  conclude  that,  during  fasting,  the 
lymph  and        lacteals  transmit  lymph,  and  the  conclusion  gives  force  to 
the  observation  already  made,  that  the  albumen  of  chyle  is 
derived  rather  from  the  blood  capillaries  than  from  the  digested  food. 
Comparison  of       ^n  comParmg  together  the  salts  of  the  serum  of  the  blood 
the  lymph  and  and  those  of  the  lymph  as  obtained  from  the  horse,  they  ap- 
pear to  coincide. 

Salts  of  Serum  and  Lymph. 


Scrum. 

Lymph. 

Alkaline  chlorides 

4  055 

4  123 

Alkaline  carbonates  

1.130 

1  135 

Alkaline  sulphates 

311 

233 

Alkaline  phosphates  

.115 

120 

5.611 

5.611 

From  the  indications  presented  in  these  tables,  there  can  be  no  doubt 
that  the  office  of  the  lymphatics  is  to  collect  the  albuminous 

Office  of  the  •      x 

lymphatic  sys-  matters  which  have  every  where  transuded  from  the  blood- 
vessels, or  been  set  free  by  changes  going  on  in  the  soft 
parts.  Such  matters,  though  they  may  be  regarded  as  being  in  one 
sense  dead,  are  yet  as  applicable  for  the  further  support  of  the  mechan- 
ism as  are  the  albumenoid  bodies  introduced  as  food,  and  said  to  be 
taken  up  by  the  lacteals.  The  last  table  shows  that  the  lymph  is  really 
nothing  but  a  diluted  serum.  A  mechanism  is  therefore  resorted  to  to 
turn  this  collected  albumen  into  fibrin,  and  thus  arises  a  lymphatic  gland 
— a  contrivance  which  tends  greatly  to  compactness.  This  structure  is 
Structure  of  ^ie  counteiTart  °^ tne  mesenteric  or  lacteal  gland.  It  may  be 
lymphatic  described  as  originating  from  the  coalescence  of  two  or  three 
lymph  vessels,  which,  casting  off  their  external  coat  as  they 
enter  the  gland,  anastomose  with  one  another  in  various  ways,  so  as  to 
form  plexuses  and  convolutions.  The  capsule  of  the  gland,  strengthen- 
ed by  the  coat  it  has  received  from  the  entering  vessels,  sends  forth  par- 
tition-like processes,  which  dip  down  into  the  grayish  pulpy  material 
filling  the  interstices.  On  their  emergence  from  the  gland  the  vessels 
recover  from  it  their  external  coat,  and,  during  their  passage  through  it 
in  their  naked  state,  blood-vessels  are  distributed  upon  them.  The  ob- 


THE   LYMPHATIC   SYSTEM. 


97 


ymphatics  of  the  largo  intestine. 


ject  of  the  arrangement  seems  to  be  to  submit  the  liquid  contained  in 
the  lymph  vessel  to  the  action  of  the  pulpy  material  of  the  gland  and  ar- 
terial blood  under  the  most  favorable  circumstances,  the  thinness  of  the 
wall  and  the  convolved  plexus  being  well  adapted  to  that  end. 

Fig.  34  illustrates  the  lymphat- 
ics of  the  large  intestine,  the  ad- 
joining parts  being  cut  or  displaced 
to  display  them ;  <2,  <z,  ascending 
and  transverse  colon  drawn  aside; 
&,  £,  descending  colon  and  its  sig- 
moid  flexure  drawn  aside ;  <?,  cce- 
cum;  d,  stomach;  e,  duodenum; 
y,  jejunum  cut ;  <?,  A,  i,  lymphatics 
and  their  glands.  In  such  an  ar- 
rangement as  this,  the  lymph  is  far 
more  perfectly  exposed  to  the  in- 
fluences to  which  it  has  to  be  sub- 
mitted than  it  could  possibly  be  in 
straight  tubes.  In  reptiles,  how- 
ever, this  package  is  not  resorted 
to,  and  the  tubes,  being  spread  out, 
give  the  false  appearance  of  a  great- 
eT'cfevelopment  to  this  system  than  in  the  higher  tribes.  In  the  mam- 
malia, according  to  Professor  Goodsir,  wherever  the  lymph  tube  enters 
the  gland,  it  changes  its  internal  constitution,  losing  the  scale-like  cover- 
ing that  its  inner  coat  presented,  and  offering  a  numerbus  development 
of  nucleated  cells,  many  of  which  adhere  to  the  membrane  beneath,  but 
many  float  away  and  drift  with  the  lymph  in  its  course.  There  is  a 
constant  reproduction  of  these  organisms,  and  they  seem  to  be  connected 
with  a  diange  in  the  albumenoid  constituent  of  the  lymph,  Production  of 
turning  it  into  fibrin.  And  thus,  if  examination  is  made  of  fibrin  in  lymph 
the  lymph  before  it  enters  a  gland  and  after  it  has  passed  slands- 
through,  in  the  former  instance  it  seems  to  differ  but  little  from  the  liquor 
sanguinis,  or  serous  portion  of  the  blood,  as  has  been  already  shown,  but 
in  the  latter  fibrin  begins  to  abound. 

Professor  Goodsir's  view  is  represented  in  the  diagram,  Fig.  35,  show- 
ing the  scale-like  ep- 
ithelial cells  of  the 
lymphatic  tube  chang- 
ing into  the  nucleated 
cells  of  the  gland. 

Diagram  of  a  lymph  gland.  Evolution  of  cells  in  lymph  gland.          Fig.   36    illustrates 

the  generation  of  broods  of  cells,  some  being  attached  and  some  free. 

G 


Fig.  85. 


Fig.  36. 


98  PRODUCTION    OF   FIBRIN. 

Some  chemists,  adopting  the  views  of  Liebig  respecting  the  essential 
Fibrin  not  an  difference  "between  blood  fibrin  and  muscle  fibrin,  look  upon 
effete  body.  ^Q  former  substance,  not  as  a  histogenetic,  but  as  an  effete 
body,  a  conclusion  which,  of  course,  would  have  an  important  bearing 
upon  the  interpretation  of  the  function  of  the  glands  as  here  given,  as  like- 
wise upon  that  in  the  corresponding  case  of  the  chyle.  The  weight  of 
physiological  evidence  is,  however,  so  strongly  against  this  doctrine,  that 
we  are  constrained  to  retain  the  old  one,  and  therefore  to  regard  the  pro- 
duction of  fibrin  as  one  of  the  important  duties  of  the  lymphatic  system. 

The  absorbent  vessels,  whether  lacteals  or  lymphatics,  have  therefore 
its  mode  of  a  common  duty  °f  changing  albuminose  or  albumen  into 
production  and  fibrin,  and  thereby  of  compensating  for  the  constant  waste  of 
that  substance  which  is  going  on  in  the  wear  and  tear  of 
the  muscular  system.  The  constitution  of  the  urine  proves  that  the 
amount  of  muscular  fibrin  destroyed  in  short  periods  of  time  is  very 
great.  "We  can  not  estimate  the  hourly  consumption  at  less  than  62 
grains.  Such  a  waste  must  demand  an  equivalent  compensation,  if 
the  animal  mechanism  is  to  be  kept  up  unimpaired,  and  every^  care  is 
therefore  taken  to  omit  no  means  which  may  incidentally  offer  for  hus- 
banding the  necessary  materials.  The  action  of  the  lymphatics  illus- 
trates this  principle  significantly.  Passing  through  all  the  soft  solids 
where  exudation  of  albumen  from  the  blood-vessels  can  take  place,  they 
collect  the  materials  that  would  otherwise  go  to  waste,  and  add  thereto 
many  of  the  products  arising  from  the  disintegration  and  decay  of  the 
soft  parts  themselves.  Receiving  all  these,  they  transmit  them  through 
their  windings  in  the  glands,  and  thus  submit  them  to  the  action  of  the 
innumerable  cells  which  are  there  coming  into  existence.  As  in  the  egg 
of  a  bird,  in  which,  as  the  albumen  slowly  disappears,  the  muscular  tis- 
sues of  the  young  chicken  arise,  so  here  the  serous  portion  disappears, 
and  fibrin  comes  in  its  stead,  and  this  is  hurried  forward  to  the  torrent 
of  the  circulation,  and  thrown  into  the  blood-vessels,  to  be  by  them  dis- 
tributed to  all  parts  of  the  mechanism,  wherever  the  muscular  tissues  are 
in  want  of  repair. 

But,  besides  this  function  of  the  elaboration  of  fibrin,  there  can  be  no 
Cutaneous  question  that  the  lymphatics  have  other  incidental  uses, 
lymphatic  ab-  Many  facts  are  known  which  prove  that  those  of  the  skin 
exert  a  powerful  agency  in  absorbing  liquid  material.  Thus 
a  person  who  has  abstained  from  water  will,  after  he  has  immersed  his 
body  in  a  bath,  not  only  find  his  weight  increased,  but  the  sensation  of 
thirst  abated.  Instances  of  the  kind  are  on  record  where  sailors,  in  open 
boats  without  fresh  water,  have  assuaged  the  torments  of  thirst  by  im- 
mersing their  bodies  in  the  sea.  Nay,  it  is  even  asserted  that  in  certain 
conditions  water  may  thus  be  obtained  from  the  atmospheric  air,  and  in 


SELECTING  POWEK  OF  THE  ABSORBENTS.  99 

all  such  cases  every  thing  points  out  that  the  lymphatic  vessels  are  the 
avenues  through  which  the  liquid  is  introduced. 

In  what  manner  does  the  lymph  move?  In  reptiles  there  are  found 
what  are  termed  lymphatic  hearts,  which  are  merely  dilated  cause  of  the 
portions  of  a  tube  exhibiting  pulsation.  Of  these,  in  the  flow  of  lymph, 
frog,  two  pairs  may  be  discovered,  one  behind  the  hip-joint,  and  situated 
so  superficially  that  the  motions  can  be  plainly  seen ;  the  other  is  at  the 
anterior  part  of  the  chest.  The  pulsating  movements  of  these  organs,  of 
course,  impel  the  liquid  acted  on  in  the  direction  determined  by  the  valves 
with  which  the  vessels  are  so  profusely  supplied,  that  is,  to  the  general 
circulation,  and  the  lymph  finally  enters  the  blood-vessels. 

But  in  the  higher  tribes  these  organs  of  impulsion  are  absent,  and  the 
circulation  through  the  vessels  is  determined  by  the  agencies  mentioned 
in  the  case  of  the  lacteals.  1st.  By  the  constant  accumulation  of  liquid 
at  the  origin  of  the  tube ;  2d.  By  every  muscular  movement,  either  vol- 
untary or  involuntary,  which  produces  a  compression  of  the  tube,  the 
valves  all  opening  one  way,  and  therefore  causing  the  included  liquid  to 
pass  in  one  direction  only ;  3d.  By  the  exhaustive  action  at  the  mouth 
of  the  lymphatic,  arising  from  the  passage  of  the  blood.  It  ought,  per- 
haps, t^  be  prominently  pointed  out,  as  belonging  to  the  second  of  these 
es,  that  the  pulsation  of  the  arterial  trunks  adjacent  to  any  lym- 
phatic brings  the  power  of  the  heart  itself  into  operation  in  an  indirect 
way. 

Though  the  absorbents  will  receive  many  different  bodies  and  transmit 
them  to  the  veins,  the  action  does  not  take  place  in  an  in-  A  arent  ge 
discriminate  manner.  Certain  substances,  such  as  the  fats  lecting  power 
and  albumen,  find  a  ready  entrance,  but  admission  to  others  of  abs( 
is  wholly  denied.  Thus  it  has  long  been  known  that  if  coloring  matter 
be  introduced  into  the  intestine,  it  by  no  means  follows  that  the  chyle 
will  be  tinged.  If  an  animal  be  compelled  to  take  litmus-water,  the 
chyle  will  still  be  found  colorless  or  white.  On  such  facts  was  founded 
the  old  doctrine  that  these  organs  possess  a  low  species  of  intelligence, 
distinguishing  among  different  substances,  permitting  some  to  enter 
them,  and  refusing  a  passage  to  others.  Many  years  ago  I  showed  that 
these  fanciful  cases  are  capable  of  a  simple  physical  explanation.  Thus 
I  found  that  if  blue  litmus  water  was  tied  up  in  a  bladder,  or  a  piece  of 
peritoneum,  and  sunk  in  a  vessel  of  alcohol,  though  the  water  would  rap- 
idly infiltrate  into  the  alcohol,  the  coloring  matter  would  be  stopped  just 
as-  it  is  in  the  intestine.  But,  in  reality,  there  is  no  need  of  such  experi- 
ments to  satisfy  us  of  the  fictitious  nature  of  this  selecting  power.  If 
we  fill  a  lamp  half  full  of  oil  and'lult  cf  water,  :and' immerse  KriYa  wick 
long  enough  to  dip  into  both,- if  the  wick  be  previously  soaked  in  oil,  it 
will  withdraw  from  the  l#mb  oil'  alone,  and  continue  to  fro'1  so 'until  the 


100  FORMATION   OF   FIBRIN. 

lamp  ceases  to  burn ;  but  if  it  be  first  soaked  in  water,  it  will  wholly 
refuse  to  take  the  oil,  and  remove  the  water  alone,  until  all  is  escaped  by 
evaporation.  But  did  ever  any  one  impute  to  the  wick  of  a  lamp  a 
"power  of  intellectuality,  no  matter  how  obscure,  or  suppose  that  there 
is  any  thing  mysterious  in  such  a  selecting  operation  ?  A  perpetual  refer- 
ence of  the  most  common  facts  to  mysterious  agencies  has  been  the  great 
barrier  to  the  advance  of  medical  science.  This  system  was  introduced 
by  the  alchemists  and  quacks  of  the  Middle  Ages,  and  even  now  it  will 
take  many  books  and  many  years  before  physiology  can  be  rescued  from 
such  visionary  theories. 

From  the  point  to  which  our  descriptions  have  brought  us,  we  have 

Connection  of  to  reSar(^  tn^s  Part  °^ tne  absorbent  mechanism  as  connected 
lacteaisand  with  two  great  animal  functions,  motion^and  respiration. 
with  motion  Both  its  divisions,  the  lymphatics  and  the  lacteals,  in  prepar- 
and  respira-  ing  fibrin  from  albumen,  make  provision  for  the  repair  of  the 
muscular  tissues,  and  are  therefore  to  be  regarded  as  a  portion 
of  the  motive  apparatus.  But  the  lacteals  are  charged  with  a  farther 
duty,  and  in  a  double  manner  are  connected  with  the  respiratory  mechan- 
ism, for  they  not  only  introduce  fats  into  the  system,  but  give  origin  to 
the  cells  of  the  blood,  which  are  the  carriers  of  oxygen. 

We  may  therefore  close  this  chapter  with  a  few  remarks,  1st.  On  the 
connection  of  the  absorbent  system  with  the  provisions  for  motion ;  2d. 
On  its  connection  with  the  respiratory  function,  as  more  particularly  dis- 
played by  the  preparation  of  blood-cells. 

1st.  The  connection  of  the  absorbent  system  with  the  provisions  for 
motion  is  through  its  function  of  preparing  fibrin  from  albumen. 

From  the  membrane  which  lines  the  plexus  of  tubes  of  which  the  mes- 
Fabrication  enteric  and  lymphatic  glands  are  composed,  crowds  of  nucleated 
of  fibrin.  cens  are  continually  arising.  As  to  the  function  of  these  cells, 
there  can  be  little  doubt  that  it  is  in  part  to  effect  the  translation  of  a 
portion  of  albumen,  which  has  been  introduced  along  with  the  oil  glob- 
ules, into  fibrin,  and  accordingly  we  find  that  the  chyle,  analyzed 'at  dif- 
ferent parts  of  its  course,  yields  different  products.  As  has  been  stated 
already,  intercepted  before  its  passage  through  these  glands,  very  little 
fibrin  is  found,  but  collected  from  points  beyond,  the  quantity  of  fibrin 
steadily  increases  and  that  of  albumen  declines.  The  plexus  of  tubes 
has  therefore  for  its  object  to  expose  its  contents  to  the  influence  of  the 
cells. 

Now  what  are  the  chemical  conditions  under  which  the  transmutation 
of  albumen  into  fibrin  takes  place  ?  The  ^problem  is  most  clearly  pre- 
sented in  !tae  case,  of r 'the 'incubation  of  a:  bird's  egg.  The  white  of  the 
egg,  consisting  chiefly  ^of  albumen,  gradually  loses  that  form,  and  passes 
into  the  Bfattf  bi*  fibrin  as  the  \5evelo|!>nient  of  the  muscular  tissues  of  the 


FORMATION   OF  BLOOD-CELLS.  101 

young  chicken  is  effected ;  but  the  change  can  not  take  place  except  ox- 
ygen be  received  through  the  shell ;  and,  indeed,  in  all  cases  in  which  al- 
bumen passes  into  fibrin,  it  does  so  only  in  the  presence  of  oxygen. 

But  in  the  case  of  the  absorbent  glands,  from  what  source  does  the 
requisite  oxygen  come  ?  These  glands  have  just  been  de-  Manner  in 
scribed  as  plexuses  of  the  absorbent  tubes,  among  the  rami-  yhich  oxygen 
fications  of  which  arteries  and  veins  are  abundantly  distrib-  the  making  of 
uted,  the  blood  not  getting  access  to  the  interior  of  the  ab-  fibrin* 
sorbent,  but  running  in  its  own  vessels,  as  it  were,  side  by  side,  and 
branching  on  the  naked  walls  of  the  plexus ;  and,  just  as  in  the  placen- 
tal  circulation  the  arterial  blood  of  the  mother  vivifies  or  furnishes  oxy- 
gen to  the  foatal  blood,  so  in  this  instance  the  arterial  blood  enables  the 
cells  to  discharge  their  duty  of  converting  the  albumen  into  fibrin,  which 
passes  onward  to  the  general  circulation  for  the  renovation  of  the  muscu- 
lar tissues. 

Since  the  hourly  consumption  of  fibrin  may  be  taken  at  62  grains, 
the  quantity  produced  by  the  action  of  these  cells  must  be  the  same. 
We  may  therefore  affirm  that  the  fibrin-producing  mechanism  yields 
aboutjone  grain  in  each  minute  of  time. 

Contemporaneously  with  the  elaboration  of  fibrin  is  the  develop- 
ment of  the  proper  chyle  corpuscles.     Through  the  evolution  Formation  of 
of  these  and  the  absorption,  of  fat,  the  chyle  vessels  present  a   Wood-cells, 
connection  with  the  respiratory  apparatus. 

If  any  weight  is  to  be  given  to  the  views  of  Ascherson,  the  occurrence 
of  fat  globules  in  the  chyle  is  essential  to  these  cellular  productions. 
He  found  that  when  globules  of  oil  are  placed  in  a  solution  of  albumen, 
they  become  coated  over  with  a  film  of  that  substance  in  a  coagulated 
state,  and  hence  was  led  to  infer  that  this  is  the  starting-point  of  cell  pro- 
duction generally. 

The  chyle  corpuscles  are  the  embryos  of  the  true  red  blood-cells,  the 
latter  being  derived  from  them  by  gradual  development.  As  will  appear 
more  in  detail  when  we  come  to  the  description  of  the  blood,  in  verte- 
brated  animals  there  are  two  distinct  classes  of  red  blood-  Twosuccessive 
cells,  which  appertain  to  distinct  periods  of  life.  The  first,  forms  of  biood- 
which  are  found  in  man  previously  to  the  time  of  formation  Cl 
of  the  chyle  and  lymph,  are  nucleated,  and  have  the  power  of  reproduc- 
tion by  fissuring  of  the  nucleus. 

But  a  distinct  set  gradually  replaces  the  preceding.  These  cells  have 
no  nucleus ;  they  are  flattened,  bi-concave,  and  in  man  circular.  They 
possess  no  power  of  reproduction  either  by  fissuring  or  otherwise.  Their 
origin  is  from  the  chyle  corpuscle,  the  granular  interior  of  which  clears 
up,  and  is  succeeded  by  a  deep  red  tint.  The  transition  from  the  first 
to  the  second  of  these  forms  takes  place  at  an  early  period,  and  may  be 


102  ABSORPTION   BY  THE   BLOOD-VESSELS. 

regarded  as  complete  in  the  human  embryo  of  two  months  old.  After 
that  time  "blood-cells  are  generated  upon  the  second  plan,  from  the  chyle 
corpuscles  alone. 

It  is  a  significant  circumstance  that  this  transition  from  the  reproduc- 
tive to  the  non-reproductive  blood-cell  is  coincident  usually  with  the  dis- 
appearance of  the  external  branchia3,  or  the  closing  of  the  branchial  fis- 
sures. There  can  be  no  question  that  the  destined  function  of  the  per- 
fect blood-cell  is  the  introduction  of  oxygen  to  the  system.  In  their  or- 
igin and  in  their  object  they  are  therefore  in  relation  with  the  respiratory 
mechanism. 


CHAPTER  VI. 

ABSOKPTION  BY  THE  BLOOD-VESSELS. 

Proof  of  Absorption  by  the  Blood  Capillaries. — Occurs  as  a  physical  Necessity. — Nature  of  Cap- 
illary Attraction. — Its  Phenomena  in  the  Rise  and  Depression  of  Liquids. —  Conditions  for 
producing  a  Flow  in  a  Capillary  Tube. — Passage  of  Liquids  through  minute  Pores. — General 
Propositions  respecting  Capillary  Attraction. — Endosmosis  and  Exosmosis. — They  depend  on 
Capillary  Attraction. — Force  against  which  these  Movements  may  take  place. — Illustrations  of 
selecting  Power. — General  View  of  the  entire  Function  of  Absorption,  lacteal  and  venous. 

THAT  the  blood-vessels  of  the  stomach  and  intestinal  tube  participate 
Substances  are  in  the  function  of  absorption  is  demonstrated  by  many  dif- 
the^bbodX-  ferent  facts*  Medicaments  placed  in  the  stomach  after  its 
iiiaries.  pyloric  orifice  has  been  tied  will  produce  their  specific  effect 

almost  as  rapidly  as  under  natural  circumstances ;  and,  since  there  are 
no  proper  lacteals  upon  that  organ,  and  its  lymphatics  seem  to  be  inade- 
quate, the  absorption  of  these  agents  can  have  taken  place  through  the 
blood-vessels  only. 

This  conclusion  is  substantiated  by  an  examination  of  the  blood  of 
the  gastric  and  mesenteric  veins.  It  varies  with  the  'stage  of  diges- 
tion and  the  nature  of  the  food.  At  first  there  is  a  general  lowering  of 
the  percentage  amount  of  the  solid  ingredients,  this  being  evidently  the 
result  of  the  absorption  of  water.  At  a  more  advanced  period,  the  rela- 
tive proportion  of  albumen,  or  rather  of  albuminose,  rises,  and  along  with 
it  the  extractive,  gelatine,  and  sugar  increase.  As  with  the  chyle  in  the 
lacteals,  so  with  the  blood  in  the  mesenteric  veins,  coagulation  takes 
place  imperfectly,  or  perhaps  not  at  all.  It  is  stated  that  the  mesen- 
teric blood  of  a  fasting  animal  does  not  differ  from  the  ordinary  venous 
blood. 

The  position  of  the  blood-vessels,  both  on  the  mucous  surface  of  the 
stomach  and  particularly  on  the  villi  of  the  intestine,  is  favorable  to  the 


PHYSICAL  NECESSITY   OF  VASCULAR  ABSORPTION.  103 

discharge  of  this  function.  The  term  venous  absorption,  employed  to 
express  it,  is  perhaps  somewhat  incorrect,  since  there  is  no  reason  that  a 
venous  capillary  should  have  any  advantage  over  an  arterial  one  in  this 
respect.  The  rapidity  with  which  substances  in  a  state  of  solution  are 
taken  up  from  these  cavities  has  been  well  demonstrated  by  such  in- 
stances as  those  of  the  detection  of  the  ferrocyanide  of  potassium  in  the 
urine  within  2  J  minutes  of  its  having  been  deposited  in  the  stomach,  or 
by  the  death  of  dogs  in  a  similar  short  period  after  strong  alcohol  had 
been  administered  to  them,  their  blood  being  found  to  be  charged  with 
that  combustible  substance. 

Among  substances  thus  finding  their  way  into  the  circulation  by  di- 
rect vascular  absorption  may  be  enumerated  such  soluble  salts  as  have 
little  affinity  for  the  tissues,  mineral  and  organic  acids,  alcohol,  ether, 
volatile  oils,  vegetable  alkaloids,  and  coloring  matters,  as  those  of  rhu- 
barb, madder,  gamboge. 

In  fact,  if  there  were  not  these  physiological  considerations,  we  should 
have  to  admit  absorption  by  the  blood-vessels  as  a  mat-  Absorption  by 
ter  of  physical  necessity ;  for,  under  the  circumstances  of  the  Wood-ves- 

.   /^r        .  i     '  t  -i    se^s  occurs  as  a 

theirsituation,  they  must  take  up  soluble  matters  presented  physical  neces- 
to  them.     Through  the  pores  of  their  delicate  structure  sub-  sit-y- 
stances  in  the  liquid  state  will  pass  to  mingle  with  the  blood. 

Though  we  have  treated  of  respiratoiy  or  lacteal  absorption  as  specif- 
ically distinct  from  absorption  by  the  blood-vessels,  the  circumstances 
here  alluded  to  evidently  point  out  that  the  resulting  action  of  the  villi 
of  the  intestines  is  of  a  mixed  kind ;  for,  though  the  epithelial  cells  and 
the  commencing  pouch  of  the  lacteal  may  exert  a  definite  influence,  the 
network  of  blood-vessels  which  lies  immediately  beneath  the  epithelium 
must  be  engaged  in  precisely  the  same  manner  as  the  network  of  blood- 
vessels between  the  gastric  follicles.  The  permeation  of  the  walls  of 
these  tubes  by  substances  in  a  state  of  solution  is  dependent,  as  we  are 
now  to  see,  upon  a  purely  physical  principle,  which  is  just  as  applicable 
in  the  one  case  as  it  is  in  the  other.  The  leading  solid  ingredients  of 
the  chyle  being  fat  and  albumen,  the  former  is  perhaps  introduced  by  the 
proper  lacteal  structure,  and  the  latter,  taken  up  by  the  vascular  network, 
exudes  in  part  again  from  it  into  the  lacteal  arrangement. 

In  the  case  of  absorption,  as  in  that  of  respiration,  hereafter  to  be  de- 
scribed, there  is  a  physical  principle  in  operation  which  it  is  necessaiy 
to  understand.  I  shall  proceed  to  explain  it  on  this  occasion  as  far  as  is 
needful  for  the  present  purpose,  and  complete  the  description  in  the  chap- 
ter on  the  function  of  respiration.  The  peculiar  views  here  set  forth, 
so  far  as  they  differ  from  those  ordinarily  expressed,  I  believe  to  be 
warranted  by  my  own  experiments  elsewhere  published. 

The  absorbent  action  of  the  blood-vessels  depends  on  the  force  known 


104 


CAPILLAEY   ELEVATIONS   AND  DEPRESSIONS. 


Fig.  ST. 


Capillary    among  physical  writers  as  CAPILLARY  ATTRACTION.     Its  nature 
attraction.  may  -foe  illustrated  as  follows : 

If  a  piece  of  glass  be  laid  on  the  surface  of  quicksilver,  it  is  so  power- 
fully attracted  thereto  as  to  require  the  exertion  of  considerable  force  to 
lift  it  off.  Natural  philosophers  generally  regard  this  as  a  force  sui  ge- 
neris, and  speak  of  it  under  the  title  of  capillary  attraction.  I  believe  it 
is  nothing  but  an  ordinary  electrical  phenomenon,  since,  if  the  glass  be 
examined,  it  will  be  found  to  be  in  a  positively  electrified  state,  and  the 
quicksilver  negative,  and  under  the  general  law  of  electricity,  known  as 
that  of  Dufay,  attraction  must  be  the  result. 

If  the  glass  be  laid  upon  the  surface  of  water,  there  is 
an  attraction  as  before.  On  lifting  it,  however,  there  is 
no  electrical  manifestation;  The  reason  of  this  is  plain. 
On  examining  this  glass,  it  will  be  found  that  no  true 
separation  of  it  from  the  water  has  taken  place.  A  film 
of  water  is  still  attached  to  it,  or,  in  other  words,  it  is 
wetted. 

If  a  slender  glass  tube,  £,  Fig.  37,be  dippedinto  a  liquid, 
Elevation  and  a,  a,  which  can  not  wet  it,  as,  for  example, 
ilqSlrca^.  quicksilver,  the  liquid  is  depressed  as  at  c, 
maiy  tubes,     and  does  not  rise  to  its  proper  hydrostatic  Depression  of  a  non. 
level,  or,  perhaps,  altogether  refuses  to  enter  the  tube.         wetting  liquid. 

Fig.  ss.  If  a  slender  glass  tube,  b,  Fig.  38,  be  dipped  into 

a  liquid, «,  #,  which  can  wet  it,  as,  for  example,  water, 
the  liquid  at  once  rises  in  the  tube,  as  at  c,  to  a  height 
which  is  greater  in  proportion  as  the  diameter  of  the 
tube  is  less.  It  is  this  phenomenon  which  has  given 
the  designation  capillary  attraction,  because  it  is 
best  seen  in  tubes  as  fine  as  a  hair  (capillus). 

Now  if  there  be  a  tube  of  such  a  diameter  that  it 
could  thus  lift  water  ten  inches,  and  it  be  broken  off 
so  as  to  be  only  six  inches  long,  we  might  inquire 
whether  the  water  would  overflow  from  its  top,  or 
simply  remain  suspended. 
Mathematical  considerations  as  well  as  direct  experiments  prove  that, 
in  such  a  case,  there  would  be  no  overflow.     A  capillary  tube  under 
these  circumstances  simply  lifts  the  water,  but  can  not  produce  a  contin- 
uous current. 

But  if  a  removal  of  the  water  at  the  top  of  the  tube  takes  place  in  any 
Conditions  for  manner»  as>  f°r  instance,  by  evaporation,  or  by  being  dissolved 
producing  a      away,  then  a  continuous  current  is  produced.     This  fact  ex- 
plains the  phenomena  of  endosmosis,  presently  to  be  de- 
scribed. 


Elevation  of  a  wetting 
liquid. 


PASSAGE   OF  WATER  THROUGH   CREVICES.  105 

As  illustrative  of  the  production  of  a  continuous  flow,  we  may  cite  the 
case  of  a  spirit-lamp,  the  wick  of  which  may  "be  regarded  as  a  bundle  of 
capillary  tubes.  If  the  cover  of  the  lamp  be  taken  off,  all  the  spirit  will 
pass  up  the  wick  and  escape  by  evaporation.  Or  in  an  oil-lamp,  the  wick 
of  which  becomes  readily  saturated  with  the  liquid,  but  never  exhibits 
any  overflow,  on  the  lamp  being  kindled,  the  oil  is  burned  off,  and  a  cur- 
rent is  at  once  established. 

I  have  shown  that  water  will  pass  through  a  crevice,  the  width  of  which 
is  less  than  one  half  of  the  millionth  of  an  inch.  Pores  or  Liquids  pass 
crevices  of  such  a  dimension  are  invisible  even  with  a  micro-  ^inut^crev7 

SCOpe.  ices  or  pores. 

The  evidence  in  proof  of  this  is  very  readily  obtained  experimentally. 
Fig.  39. If  -we  take  a  convex  lens,  a,  a,  of 

Passage  of  water  through  a  crertce.  point  of  Contact,  C,  On  looking  down 

upon  the  arrangement,  a  black  spot  surrounded  by  a  series  of  variously 
colored^oireentric  circles,  the  appearance  being  well  known  among  op- 
tical writers  underlie  name  of  Newton's  colored  rings.  At  the  point 
of  apparent  contact,  <?,  the  lens  and  the  plane  are,  as  Newton  has  shown, 
a  distance  apart  of  about  the  one  half  of  the  millionth  of  an  inch,  and 
from  this  central  point,  proceeding  outwardly,  the  distance  between  the 
glasses,  of  course,  increases.  If  any  where  at  the  outer  portion  a  drop 
of  water  be  introduced,  it  extends  itself  instantly  across  all  the  colored 
rings,  reaching  even  across  the  central  black  spot. 

The  three  following  general  propositions  present  those  phe-  General  propo- 
nomena  of  capillary  attraction  which  are  most  interesting  in  j^^uiyry*' 
a  physiological  point  of  view.  attraction. 

1st.  If  the  force  of  attraction  of  the  particles  of  a  solid  for  those  of  a 
liquid  be  not  equal  to  half  the  cohesive  force  of  the  latter  for  each  other, 
the  liquid  will  refuse  to  pass  through  a  pore  of  that  solid  substance,  and, 
in  a  capillary  tube  consisting  of  it,  will  be  depressed  below  its  hydro- 
static level. 

2d.  If  the  force  of  attraction  of  the  particles  of  a  solid  for  those  of  a 
liquid  exceeds  half  the  cohesive  force  of  the  latter  for  each  other,  but  is 
not  equal  to  the  whole  force,  the  liquid  will  pass  through  a  pore  of  that 
solid  substance,  and,  in  a  capillary  tube  of  it,  will  rise  above  its  hydro- 
static level. 

3d.  If  the  force  of  attraction  of  the  particles  of  a  solid  for  those  of  a 
liquid  exceeds  the  whole  cohesive  force  of  the  latter,  chemical  union  be- 
tween them  ensues. 

It  would  not  be  consistent  with  the  plan  of  this  work  to  offer  a  dem- 
onstration of  these  propositions ;  nevertheless,  they  are  capable  of  rigor- 


106  ENDOSMOSIS   AND  EXOSMOSIS. 

ous  mathematical  and  physical  proof.  The  views  I  am  here  presenting 
enable  us  to  include  the  pressures  between  solids  and  liquids,  the  rise  or 
depression  of  liquids  in  capillary  tubes,  and  the  phenomena  of  chemical 
affinity  in  the  same  general  expression.  And  such  a  co-ordination  is  the 
more  valuable,  since  there  has  been  a  disposition  among  physiologists  to 
regard  the  introduction  of  material  through  the  pores  of  organized  textures 
as  dependent  on  some  ill-defined  or  mysterious  principle. 

The  phenomena  of  endosmosis,  first  brought  to  general  notice  in  the 
Endosmosis  case  of  liquid  substances  by  M.  Dutrochet,  may  be  explain- 
and  exosmosis.  e(j  as  follows :  If  some  alcohol  be  placed  in  a  bladder,  the 
neck  of  which  is  tightly  tied,  and  the  bladder  be  sunk  in  a  vessel  of 
water,  a  percolation  ensues,  so  that  the  bladder  distends  to  its  utmost 
capacity,  and  might  even  be  burst.  Or,  which  is  a  better  method  of 
showing  the  result,  if,  instead  of  tying  the  mouth  of  the  bladder,  a  glass 
tube,  open  at  both  ends,  and  a  foot  or  two  long,  be  fastened  into  it  with- 
out leakage,  as  the  water  introduces  itself  through  the  pores  of  the  blad- 
der to  mingle  with  the  alcohol,  the  liquid  rises  in  the  glass  tube,  sup- 
posed to  be  left  in  a  vertical  position,  and,  when  it  has  reached  the  top  of 

it,  overflows.  To  express  this  inward  pas- 
sage of  the  water  the  term  endosmosis  was 
introduced,  and  since  a  little  of  the  alcohol 
simultaneously  passes  outward  to  mix  with 
the  water,  it  is  said  to  exhibit  exosmosis. 

In  Fig.  40  is  represented  the  endosmome- 
ter  of  Dutrochet.  It  consists  of  a  small  blad- 
der, #,  tightly  tied  to  a  tube,  d,  which  is  open 
at  both  ends,  and  bent,  as  seen  in  the  figure 
at  c  ;  the  bladder  being  completely  filled  with 
alcohol,  and  the  tube  to  some  such  point  as 
d,  the  arrangement  is  to  be  placed  in  a  ves- 
sel of  water,  e  e;  almost  immediately  the  level 
of  ^  jig^  w{\\  fa  seen  to  be  rising,  the 
bend  of  the  tube  is  reached,  and  one  drop  after  another  falls  from  the  open 
end  into  the  glass,  b.  And  this  continues  until  the  liquids  inside  and 
outside  of  the  bladder  are  uniformly  commingled. 

It  is  to  be  regretted  that  the  terms  endosmosis  and  exosmosis  have 
These  move-  "been  accepted  by  physiological  writers,  for  in  these  results 
ments  are  de-  faQrQ  ^  nothing  more  than  what  we*  should  expect  from  the 

pendent  on  ca-  .    ,  ^          .,,  .  mi  e 

piliary  attrac-  known  principles  of  capillary  attraction.  The  pores  01  a 
tlon-  bladder,  or  of  any  other  such  organic  texture,  are  nothing  but 

short  capillary  tubes  into  which  water  readily  finds  its  way,  because  it 
can  wet  the  substance  surrounding  the  pore.  If  the  bladder  be  distended 
with  air,  and  sunk  under  water,  although  the  water  will  fill  the  pores,  it 


FORCE   OF   ENDOSMOTIC  MOVEMENT.  107 

will  not  exude  from  them,  and  accumulate  in  the  interior  of  the  viscus, 
for,  as  we  have  seen,  a  capillary  tube  can  not  establish  a  continued  cur- 
rent or  flow.  But  the  case  becomes  totally  different  when  the  bladder  is 
filled  with  alcohol ;  for  then,  as  fast  as  the  water  presents  itself  on  the  in- 
ner end  of  the  pore,  it  is  dissolved  away  by  the  alcohol,  and  the  necessary 
condition  for  a  continuous  flow  is  complied  with.  Meantime,  through  . 
the  pore  itself  a  little  alcohol  passes  in  the  opposite  way  by  infiltrating 
through  the  incoming  water,  provided  that  the  current  be  not  too  strong, 
and  so  endosmosis  of  the  water  and  exosmosis  of  the  alcohol  take  place, 
the  current  of  the  former  greatly  preponderating  over  that  of  the  latter, 
and  an  accumulation  of  liquid  in  the  interior  of  the  bladder  ensues. 

That  in  all  this  there  is  nothing  specially  dependent  on  the  organic 
texture  employed  is  obvious  from  the  fact  that  the  same  results  arise 
when  any  inorganic  porous  body  is  used.  Vessels  of  unglazed  earthen- 
ware, pieces  of  baked  slate  or  stucco,  answer  the  purpose  very  well,  as 
will  also  a^glass  vessel  with  a  minute  fissure  or  crack  in  it. 

An  incorrect  representation  of  the  conditions  under  which  endosmosis 
takes  place  is  often  made.  It  is  said  to  depend  on  the  relative  specific 
gravity  of  the  liquids.  Thus  it  is  stated  that  the  lighter  liquid  always 
moves  toward  the  denser,  more  abundantly  than  the  denser  to  the  lighter. 
The  error  of  this  is  readily  shown  by  many  simple  illustrations.  Thus 
water  endosmoses  equally  well  to  alcohol,  which  is  lighter  than  it,  and  4o 
gum  water  or  salt  water,  which  are  heavier.  The  relation  of  specific 
gravity  has  nothing  whatever  to  do  with  the  action. 

The  force  with  which  a  liquid  will  thus  pass  through  a  pore  to  mingle 
with  another  liquid  beyond  is  very  great.  I  have  observed  -porce  against 
these  motions  occurring  against  a  pressure  of  many  atmos-  which  these 

A-,.,,..  ,  ^  movements 

pneres.  And,  indeed,  in  practice  we  have  no  means  of  measur-  may  take 
ing  its  actual  intensity ;  for  when  a  pressure  of  a  certain  de-  Place- 
gree  has  accumulated,  hydraulic  leakage  takes  place  backward  through 
the  pore,  and  conceals  the  true  action. 

From  the  preceding  statements  respecting  capillary  attraction  and  en- 
dosmosis, we  may  therefore  conclude  that,  whenever  a  liquid  is  in  con- 
tact with  a  porous  body  the  substance  of  which  it  can  wet,  it  will  freely 
pass  into  the  pores  thereof,  and,  if  the  necessary  conditions  for  its  re- 
moval are  present,  will  percolate  or  transfuse  with  very  great  mechanical 
power ;  that  this  will  take  place  through  pores  that  are  not  only  invis- 
ible to  the  eye,  but  imperceptible  by  the  aid  of  the  microscope ;  that 
some  liquids  pass  thus  with  more  readiness,  some  with  less,  some  not  at 
all — the  result  in  these  respects  depending  on  the  electro-chemical  rela- 
tions subsisting  between  them  and  the  solid  they  are  in  contact  with, 
and  their  own  force  of  cohesion;  that  organic  membranes  present  no 
peculiarities,  their  action  arising,  not  because  they  are  organic,  but  be- 


108 


SELECTING   POWER   OF   MEMBRANES. 


cause  they  arc  porous ;   that  the   so-called  selecting  power  is  purely 
Fig.  41.  physical,  as  are  the  separations  and  apparent  decomposi- 

tions to  which  it  gives  rise.  When  a  drop  of  colored 
water  is  put  upon  chalk,  the  water  sinks  in,  but  the  color 
is  left  on  the  surface.  When  weak  alcohol  is  tied  up 
in  a  bladder,  the  water  will  escape  through  the  pores, 
and  the  spirit  become  anhydrous  at  last. 

If  we  take  a  glass  tube,  <2,  a,  Fig.  41,  over  the  lower 
end  of  which  a  piece  of  peritoneum,  or  other  delicate 
membrane,  &,  &,  is  tightly  tied,  and  half  fill  it  with  litmus- 
water,  and  then  place  it  in  a  glass  of  alcohol,  c,  c,  the 
level  of  the  liquids  inside  and  outside  being  adjusted  ac- 
cording to  their  specific  gravity,  so  that  there  may  be  no 
hydrostatic  pressure  either  one  way  or  the  other  through 
the  pores  of  the  peritoneum — as  soon  as  the  arrangement 
is  completed,  if  the  observer  be  so  placed  as  to  view  it  by 
transmitted  light,  he  will  see  the  water  descending  from 
the  pores  of  the  peritoneum  in  stride  and  streams  through 

Selecting  power  of  a  r  r 

membrane.  the  alcohol  in  a  perfectly  colorless  state.  Th6  membrane, 
therefore,  has  absorbed  and  transmitted  the  water,  but  has  refused  to 
the  coloring  matter  a  passage.  It  is  to  this  particular  experiment  that 
a^usion  was  made  when  speaking  of  the  non-coloration  of  the  chyle 
when  certain  coloring  material  had  been  mixed  with  the  food.  Such 
illustrations  may  therefore  satisfy  us  that  the  selecting  power  of  organic 
porous  textures,  like  that  of  inorganic  ones,  is  dependent  on  simple 
physical  circumstances,  and  for  these  reasons  I  exclude  from  the  mech- 
anism of  animal  absorption  the  influence  of  any  vital  or  other  mysterious 
principle,  and  adopt  the  sentiment  of  the  Abbe  Hauy,  that  "those  specious 
causes  and  imaginary  powers,  to  which,  in  the  Middle  Ages,  all  natural 
phenomena,  even  those  of  an  astronomical  kind,  were  referred,  but  which, 
through  the  genius  of  Newton  and  Laplace,  have  been  banished  from  the 
celestial  spaces,  have  taken  their  last  refuge  in  the  recesses  of  organic 
beings,  and  from  these  retreats  positive  philosophy  is  preparing  to  expel 
them." 

In  view  of  all  the  preceding  facts,  I  therefore  regard  absorption  by  the 
Summary  of  blood-vessels  as  taking  place  of  necessity,  because  of  the  po- 
tts nature  of  rous  structure  of  those  tubes ;  for,  though  the  pores  may  be 
too  small  to  be  discerned  even  by  microscopic  aid,  they  are 
abundantly  large  enough  to  permit  such  a  percolation.  Whatever  ma- 
terial is  existing  in  the  chyme  in  a  state  of  solution  in  water  and  also 
soluble  in  the  blood,  passes  through  the  walls  of  the  vessels,  and  is  moved 
toward  the  liver,  its  percolation  being  greatly  facilitated  by  the  onward 
motion  of  the  blood,  in  which  liquid  it  is  dissolved  as  fast  as  it  presents 


COURSE   OF  ABSORBED  MATERIAL.  109 

itself.  The  double  condition  here  specified  must  be  complied  with ;  the 
material  to  be  introduced  must  be  dissolved  in  water,  and  must  be  sol- 
uble in  the  blood.  If  the  latter  condition  be  wanting,  the  vessels  seem 
to  manifest  a  selecting  power,  absorption  not  taking  place,  as  in  the  case 
of  litmus,  presented  above  as  an  illustration — a  coloring  matter  which, 
though  soluble  in  water,  is  not  soluble  in  alcohol,  and  so  can  not,  under 
those  circumstances,  pass  through  a  piece  of  bladder. 

While  thus  there  is  an  introduction  of  digested  material  from  the  stom- 
ach and  intestine  into  the  blood,  the  physical  principles  which  are  guid- 
ing us  in  our  explanation  teach  us  that  there  must  be  a  percolation  of 
the  more  watery  portions  of  the  blood  in  the  opposite  direction — that  is, 
into  the  digestive  cavity.  There  is  every  reason  to  believe  that  this 
percolation  is  to  a  far  greater  amount  than  is  generally  supposed.  Under 
certain  circumstances,  it  is  a  matter  of  ordinary  observation  that  the  wa- 
ter discharged  from  the  intestine  is  more  in  quantity  than  that  which  has 
been  taken  as  drink^ 

Turning  our  attention  now  to  the  course  which  is  followed  by  the  liq- 
uid which  has  been  introduced  from  the  digestive  cavity  Course  of  the 
into  the  blood-vessels,  we  must  bear  in  mind  that  the  con-  absorbed  mate- 
tent  of  those  vessels  is  composed  of  two  distinct  portions,  "**  ^dificaT" 
the  matter  thus  recently  introduced,  and  the  original  venous  tions  it  under- 
blood.  These  together  make  their  way  through  the  portal  goes 
vein  to  the  liver,  a  gland  of  double  function,  and,  as  we  may  say  in  this 
respect,  of  double  structure ;  for,  though  it  has  a  duct  for  the  disposal 
of  the  products  which  arise  from  its  action  on  one  portion  of  the  material 
thus  brought  to  it,  the  venous  blood,  it  is  ductless  as  regards  the  other 
portion,  which  has  been  received  from  the  digestive  cavity.  This  portion, 
under  the  influence  of  the  cell  structure  of  the  liver,  undergoes  profound 
modification ;  for  instance,  liver-sugar  makes  its  appearance,  though  none 
existed  before.  It  is  not  necessary  for  us  to  specify  these  changes  par- 
ticularly here,  since  we  shall  have  to  examine  them  more  in  detail  in  a 
subsequent  chapter ;  but  it  may  be  observed  that  the  anatomical  pe- 
culiarity of  the  liver  in  this  branch  of  its  duty  is,  that  it  simply  impresses 
a  change  on  the  compounds  thus  brought  to  it,  gives  rise  to  no  excretions, 
and  therefore  has  no  channel  or  duct  of  escape,  unless  indeed  we  say,  as 
we  are  actually  justified  in  doing,  that  the  hepatic  veins  themselves  are 
the  ducts  of  the  liver  in  this  respect. 

Though  it  does  not  strictly  appertain  to  the  subject  of  which  we  are 
now  speaking,  absorption,  we  may,  for  the  sake  of  completeness,  describe, 
in  a  superficial  manner,  what  occurs  to  the  other  constituent  of  the  portal 
blood,  its  proper  venous  portion.  This,  brought  into  the  liver,  is  acted 
upon  by  that  organ  and  decomposed  into  two  portions,  one  of  which,  con- 
stituting the  bile,  is  brought  back  eventually  through  the  proper  bile  duct 


110  SUMMARY  OF  ABSORPTION. 

into  the  intestine.  The  other  is  carried  into  the  blood  circulation.  I  be- 
lieve that  this  separation  is  of  a  purely  physical  kind,  and  is  accomplish- 
ed by  mere  filtration,  the  elements  of  the  bile  all  pre-existing  in  the  blood. 
However  that  may  be,  the  separation  in  a  chemical  sense  is  very  distinct, 
for  the  nitrogenized  ingredients  are  saved  to  the  system,  and  earned  into 
the  general  circulation  through  the  hepatic  veins ;  but  the  biliary  mate- 
Return  of  a  Ild^  Brought  kack  int°  tne  intestine  is  a  hydrocarbon  tinctured 
part  to  the  with  a  little  coloring  matter,  which,  being  on  a  rapid  career  of 
retrograde  metamorphosis,  is  prone  to  act  as  a  ferment,  and 
therefore  unfit  to  remain  in  the  system ;  accordingly,  it  is  removed  with 
the  excrement.  The  other  portion,  the  hydrocarbon,  which  has  been 
brought  into  the  intestine,  is  not  yet  done  with ;  advantageous  use  can 
still  be  made  of  it.  It  can  aid  in  the  introduction  of  fats  through  the 
villi  into  the  lacteals,  and,  from  its  combustible  nature,  is  of  an  equal  value 
to  the  system  with  the  oils  it  thus  helps  to  introduce.  We  may  advan- 
tageously trace  the  course  which  it  follows,  for  in  so  doing  we  shall  com- 
plete our  description  of  the  function  of  absorption  in  its  most  general 
sense. 

The  fat  matters  which  have  been  subdivided  into  portions  of  micro- 
Manner  of  sc°pical  minuteness,  small  globules,  each  of  which  is  coated 
action  of  over  with  a  delicate  film  of  albumen,  and  all  brought  therefore 
*'  into  the  state  of  an  emulsion,  can  make  their  way  by  reason  of 
the  peculiar  properties  of  the  investiture  which  thus  covers  them  through 
the  pores  of  the  villi  into  the  lacteal.  For  my  own  part,  I  do  not  believe 
that  there  is  any  passage  through  the  epithelial  cells,  but  that  it  is  en- 
tirely interstitial,  and  that  it  is  not  unlikely  that  the  biliary  constituent 
aids  in  this  progress.  It  signifies  nothing  that  the  spaces  through  which 
the  fat  globules  have  to  go  are  less  than  their  own  diameter ;  they  can 
elongate  into  worm-like  forms,  just  as,  under  the  same  circumstances, 
blood-cells  can  do,  and,  the  moment  they  reach  the  cavity  of  the  lacteal, 
reassume  their  sphericity  by  reason  of  their  cohesion.  The  albumen 
that  now  accompanies  them  in  the  liquid  form,  as  the  other  chief  ingre- 
dient of  the  chyle,  comes,  for  the  most  part,  from  the  blood-vessels  of 
the  villi.  The  chyle  moves  onward  to  the  mesenteric  glands,  and  makes 
its  passage  through  them  either  in  naked  tubes  or  through  their  pulpy 
structure,  is  submitted  to  cell  action  and  to  arterial  blood,  undergoes  the 
morphological  changes  which  have  been  described  in  the  preceding  chap- 
ter, and,  gaining  the  thoracic  duct,  is  brought  into  the  general  circula- 
tion. 

In  the  description  here  offered  of  the  function  of  absorption,  the  agen- 
cy of  physical  forces  alone  has  been  considered,  and  these  I  conceive  to 
be  abundantly  sufficient  to  enable  us  to  account  for  all  the  phenomena. 


THE   BLOOD.  Ill 


CHAPTER  VII. 

OF  THE  BLOOD. 

The  Offices  and  Relation  of  Blood  in  the  System. —  The  Plasma  and  Cells. — General  Properties 
and  Composition  of  the  Blood. — Quantity  in  the  Body. — Coagulation. — Blood-cells. — Their  suc- 
cessive Forms. — TJie  perfect  Cell. — Hcematin:  its  Properties. — Number  of  Blood-cells. — Plas- 
ma :  its  Composition,  and  Variations  of  its  Ingredients. — Albumen,  Fibrin,  Fat,  Sugar. — Min- 
eral Ingredients  of  the  Cells  and  Plasma  compared. — Gases  of  the  Blood. —  Changes  occurring 
during  the  Circulation. — General  Functions  of  the  different  Ingredients  oftheBhod. — Introduc- 
tion of  Oxygen  by  the  Cells. — Tlieir  transient  Duration. 

IT  is  necessary  for  the  functional  activity  of  every  organized  being  that 
there  shall  circulale-throjigh  all  parts  of  it  a  nutritive  liquid.  In  plants, 
it  is  the  sap ;  in  animals,  the  blood. 

Since  the  life  of  plants  manifests  itself,  for  the  most  part,  in  a  purely 
formative  result,  and  involves  little  or  no  destruction  of  parts,  The  blood:  its 
the  circulating  current  is  devoted  almost  entirely  to  nutrition,  functions. 
But  in  animals,  whose  conditions  of  existence  involve  extensive  and  un- 
ceasing destruction,  the  current  is  burdened  with  another  duty.  It  is 
also  the  means  of  removal  of  dying  or  wasted  portions. 

In  the  first  chapter  it  was  shown  that  about  a  ton  and  a  half  of  mate- 
rial is  required  by  a  man  in  the  course  of  a  year,  and  that  in  introduction 
the  same  period  a  like  amount  is  removed  from  the  system,  ^grki'bythe 
When  we  reflect  that  the  introduction  and  removal  of  this  blood, 
immense  mass  is  accomplished  through  the  agency  of  the  circulating 
blood,  it  is  obvious  that  that  fluid  must  be  undergoing  the  most  rapid 
changes.  The  rapidity  with  which  dying  matters  are  removed  is  strik- 
ingly illustrated  by  the  minute  extent  to  which  they  are  permitted  to  ac- 
cumulate in  a  healthy  state.  These  elements  of  decay  are  strained  off 
or  exhaled  as  quickly  as  they  arise.  That  fancied  power,  the  "  vis  med- 
icatrix  naturae,"  is  only  an  ideal  expression  of  the  perfection  with  which 
the  various  eliminating  mechanisms  work.  Poisonous  agents,  whether 
they  have  been  introduced  from  without  or  have  originated  from  morbid 
actions  within,  like  all  other  useless  or  noxious  products,  find  their  prop- 
er channel  of  escape,  and  the  system  will  thus  rid  itself  of  intoxicating 
liquids  and  narcotic  drugs  if  their  quantity  does  not  exceed  the  amount 
that  it  can  destroy  or  excrete  in  a  special  period  of  time. 

Considered  in  its  relation  to  nutrition,  the  circulating  liquid  presents 
many  interesting  aspects.  Each  of  the  thousand  variously-constituted 
parts  of  the  body  is  withdrawing  the  supplies  it  needs :  the  muscular,  the 


112  PKOPERTIES  OF  THE  BLOOD. 

interconnect  nervous,  the  cartilaginous,  the  bony ;  and  hence  there  arises 
thro^h^hiT*8  a  genera^  balance  in  the  system,  each  part  making  its  demand 
circulation.  at  a  certain  rate,  and  each  observing  a  complementary  ac- 
tion to  all  the  rest.  Many  of  those  phenomena  which,  in  the  infancy  of 
physiology,  were  regarded  as  instances  of  sympathy  between  different 
parts,  are  clearly  dependent  on  these  conditions  ;  for  the  development  of 
one  part,  by  abstracting  special  material  from  the  circulating  liquid,  per- 
mits the  co-ordinate  development  of  another,  or  perhaps  puts  a  stop  to 
it.  The  minutest  portion  of  the  mechanism  is  thus  indissolubly  con- 
nected with  all  the  rest  through  the  medium  of  the  blood. 

Seen  as  it  circulates  in  the  vessels,  the  blood  consists  of  a  colorless 
The  plasma  liquid  containing  corpuscles.  In  man,  some  of  these  corpuscles 
and  cells.  are  white  and  others  red.  ,  To  the  liquid  in  which  they  float, 
the  designation  of  the  plasma  is  given ;  the  colored  corpuscles,  from  their 
Properties  of  shape,  are  called  discs  or  cells.  The  specific  gravity  of  the 
the  blood.  blood  varies  from  1.050  to  1.059,  the  variation  being,  to  a  con- 
siderable extent,  due  to  variations  in  the  quantity  of  the  cells.  The 
temperature  is  about  100°  Fahr.,  the  reaction  always  alkaline ;  there  is 
also  a  faint  sickly  odor,  which  differs  in  different  animals.  The  capacity 
of  blood  for  heat  is  in  direct  proportion  to  its  density.  The  cells  give  to 
the  blood  its  tint  of  color,  and  this,  in  the  systemic  arteries,  is  crimson,  in 
the  veins,  deep  blue.  However,  the  color  of  arterial  blood  depends  con- 
siderably on  the  condition  of  respiration.  An  imperfect  introduction  of 
oxygen,  as  in  hot  climates,  causes  the  arterial  blood  to  assume  a  dark  color, 
and  the  same  is  observed  when  chloroform,  ether,  or  diluted  irrespirable 
gases  are  breathed.  The  blood  of  the  male  sex  is  heavier  than  that  of 
the  female. 

Constitution  of  tKe  Blood. 

Water 784.00 

Albumen 70.00 

Fibrin 2.20 

(Globulin 123.50 

DlSCS         tEfematin 7.50 

f  Cholesterine 0.08 

Cerebrine 0.40 

_,              J  Seroline 0.02 

I  Oleic  and  margaric  acid  J 

Volatile  and  odorous  fatty  acid  >  0.80 

I  Fat  containing  phosphorus          3 

Chloride  of  sodium 3.60 

Chloride  of  potassium 0.36 

Tribasic  phosphate  of  soda 0.20 

Salts        ^  Carbonate  of  soda 0.84 

Sulphate  of  soda 0.28 

Phosphates  of  lime  and  magnesia 0.25 

Oxide  and  phosphate  of  iron 0.50 

Extract,  salivary  matter,  urea,  biliary  coloring  >  -  ,  ~ 

matter,  accidental  substances  ) 

1000.00 


QUANTITY   OF   BLOOD.  113 

Elementary  Composition  of  dried  Ox  Blood. 

Carbon 519.50 

Hydrogen 71.70 

Nitrogen 150.70 

Oxygen 213.90 

Ashes 44.20 

1000.00 

This  table  leads  to  the  hypothetical  formula  of  the  ultimate  constitu- 
tion of  blood:  ' 

^48  H39  ^6   °15 

As  to  the  quantity  of  blood  in  the  circulation,  it  has  been  variously  es- 
timated. It  may  perhaps  be  taken  at  one  eighth  of  the  weight  Quantit  of 
of  the  body,  a  number  which  is  agreed  upon  by  several  authors,  blood  in  the 
and  in  support  of  which  Lehmann  mentions  the  following  in-  °  y" 
teresting  observation:  "My  friend,  E.  Weber,  determined,  with  my  co- 
operation, the  weights  of  two  criminals  before  and  after  decapitation.  The 
quantity  of  blood  which  escaped  from  the  body  was  determined  in  the 
following  manner :  Water  was  injected  into  the  vessels  of  the  trunk  and 
head  until  the  fluid  escaping  from  the  veins  had  only  a  pale  red  or  yel- 
low color.  The  quantity  of  blood  remaining  in  the  body  was  then  calcu- 
lated by  instituting  a  comparison  between  the  solid  residue  of  this  pale  red 
aqueous  fluid  and  that  of  the  blood  which  first  escaped.  By  way  of  illus- 
tration, I  subjoin  the  results  yielded  by  one  of  the  experiments.  The  living 
body  of  one  of  the  criminals  weighed  60, 140  grammes ;  and  the  same  body, 
after  the  decapitation,  54,600  grammes;  consequently,  5540  grammes  of 
blood  had  escaped.  28.560  grammes  of  this  blood  yielded  5.36  grammes 
of  solid  residue ;  60.5  grammes  of  sanguineous  water  collected  after  the 
injection  contained  3.724  grammes  of  solid  substances.  6050  grammes 
of  the  sanguineous  water  that  returned  from  the  veins  were  collected,  and 
these  contained  37.24  grammes  of  solid  residue,  which  corresponds  to 
1980  grammes  of  blood;  consequently,  the  body  contained  7520  grammes 
of  blood  (5540  escaping  in  the  act  of  decapitation,  and  1980  remaining  in 
the  body)  ;  hence  the  weight  of  the  whole  blood  was  to  that  of  the  body 
nearly  in  the  ratio  of  one  to  eight.  The  other  experiment  yielded  a  pre- 
cisely similar  result." 

A  short  time  after  it  has  been  drawn,  the  blood  undergoes  coagulation, 
and  is  then  said  to  be  composed  of  the  serum  and  the  clot.   Spontaneous 
In  this  state  it  is  sometimes  spoken  of  as  dead.     The  plasma  seram°andt0 
of  living  blood  differs  from  the  serum  of  dead  in  containing  clot, 
fibrin. 

The  coagulation  of  the  blood  commences  within  about  ten  minutes 
after  it  has  been  drawn,  and  the  clot  undergoes  a  subsequent  The  coaguia- 
condensation  during  one  or  two  days.  To  understand  the  tlon  of  blood- 
physical  nature  of  this  singular  change,  we  may  conveniently  regard  the 

H 


114  COAGULATION   OF   THE   BLOOD. 

living  blood  as  containing  three  leading  constituents — an  albuminousjiq- 
uid,  fibrin  dissolved  therein,  and  the  cells.  The  coagulation  arises  from 
the  tendency  of  the  fibrin  particles  to  agglutinate  together.  As  this  takes 
place,  the  cells  are  caught  in  the  meshes  of  the  network  that  arises,  and 
a  voluminous  red  clot  is  the  result.  So  the  serum  of  dead  blood  con- 
tains no  fibrin,  and  differs  from  the  plasma  of  living  blood  in  that  impor- 
tant particular. 

It  has  been  observed  that  exposure  to  cold  retards  coagulation,  as  does 
likewise  the  absence  of  air,  or  covering  the  blood  over  with  a  film  of  oil. 
The  condition  of  rest  promotes  it,  as  also  does  the  presence  of  rough  or 
angular  bodies.  Blood  will  yield  up  its  fibrin  readily  when  stirred  with 
The  buffy  a  stick.  When,  for  any  reason,  the  cells  sink  more  rapidly  than 
coat«  usual  from  the  surface  of  the  blood,  the  fibrin  of  the  supernatant 
portion  coagulates  alone,  giving  rise  to  a  stratum  free  from  the  red  color, 
and  designated  the  bufiy  coat,  and  on  the  subsequent  contraction,  since 
there  are  no  cells  to  hinder  the  fibrin,  its  parts  upon  this  stratum  are 
drawn  more  closely  together,  and  the  clot  becomes  cupped. 

By  those  who  accept  figurative  expressions  as  an  explanation  of  phys- 
Expianationof  iological  facts,  the  coagulation  of  the  blood  is  said  to  be  due 
coagulation,  f  0  j{s  death ;  some,  however,  have  regarded  it  as  an  abortive 
attempt  at  organization,  and  therefore  a  manifestation  of  life.  Such  con- 
tradictory explanations  lose  much  of  their  interest  when  we  examine  the 
facts  of  the  case  critically.  I  believe  that  nothing  more  takes  place  in 
blood  which  has  been  drawn  into  a  cup  than  would  have  taken  place  had 
it  remained  in  the  body.  In  either  case  the  fibrin  would  have  equally 
coagulated.  The  entrapping  of  the  cells  is  a  mere  accident.  The  hourly 
demand  for  fibrin  amounts  to  62  grains ;  a  simple  arithmetical  calculation 
will  show  that  the  entire  mass  of  the  blood  would  be  exhausted  of  all 
the  fibrin  it  contains  in  about  four  hours,  so  that  the  solidification  of 
fibrin  must  be  taking  place  at  just  as  rapid  a  rate  in  the  system  as  after 
it  has  been  withdrawn.  No  clot  forms  in  the  blood-vessels,  because  the 
fibrin  is  picked  out  by  the  muscular  tissues  for  their  nourishment  as  fast 
as  it  is  presented,  nor  would  any  clot  form  in  a  cup  if  we  could  by  any 
means  remove  the  fibrin  granules  as  fast  as  they  solidified. 

That  blood-fibrin  differs  from  muscle-fibrin  in  certain  respects  is  to  be 
admitted,  but  it  does  not  follow  that  blood-fibrin  is  in  a  condition  of  ret- 
rograde metamorphosis.  It  may  require  modification  before  it  can  be 
received  as  the  syntonin  of  muscles,  but  that  such  a  conversion  actually 
takes  place  I  think  there  can  be  no  doubt. 

In  entering  on  a  detailed  examination  of  the  constitution  and  func- 
tions of  the  blood,  our  attention  will  have  to  be  directed,  in  the  first 
place,  to  the  cells.  It  is  sufficient  to  arrest  our  thoughts  at  once  when 
we  learn  that  for  every  beat  of  the  pulse  nearly  twenty  millions  of  these 


SUCCESSIVE  FORMS   OF   BLOOD-CELLS.  115 

organisms  die !     Physiology  has  its  passing  wonders  as  well  as  astron- 
omy. 

In  the  life  of  man  there  are  three  periods  distinguished  from  each  other 
by  the  nature  or  structure  of  the  blood-cells.  Those  of  the  Successivc 
first  period  originate  simultaneously  with,  or  even  previously  races  of  blood- 
to,  the  heart.  These  are  sometimes  designated  as  embryo  ^ 
cells,  and  in  that  view  bear  the  same  relation  to  those  of  the  second  pe- 
riod as  do  the  lymph  corpuscles  to  those  of  the  third.  They  are  color- 
less and  spherical  cells,  containing  granules  of  fatty  material,  and  having 
a  central  nucleus.  These  are  developed,  by  a  process  of  internal  deli- 
quescence, into  cells  of  the  second  period,  which  have  acquired  a  red  col- 
or, and  in  oviparous  vertebrates  an  elliptical  form,  though  in  man  they 
are  circular.  They  are  flat  or  disc-like  in  shape,  have  a  diameter  of 
about  2-^-Q  of  an  inch,  with  a  central  nucleus  of  half  that  size.  Some- 
times they  appear  to  undergo  multiplication  by  division  of  the  nucleus. 

These  cells  of  the  second  period  are  replaced  by  those  of  the  third,  the 
transition  being  clearly  connected  with  the  production  of  lymph  and  chyle 
corpuscles.  By  the  end  of  the  second  month  of  foetal  existence  the  re- 
placement is  complete,  and  the  class  of  cells  or  discs  that  has  now  arisen 
is  continued  during  life.  The  mode  of  their  production,  according  to  Mr. 
Paget,  is  this.  The  chyle  or  lymph  corpuscle  loses  its  granular  aspect, 
and  acquires  a  pale  red  color,  which  gradually  deepens  ;  the  corpuscle  be- 
comes smooth,  loses  its  spherical  form,  and,  condensing,  takes  on  a  con- 
vex lenticular  shape,  and  eventually  a  bi-concave.  While  this  change 
of  structure  is  going  on,  the  specific  gravity  increases  through  the  con- 
densation, and  the  development  closes  by  the  spherical,  white,  granular, 
lymph  corpuscle  becoming  a  red,  bi-concave,  non-nucleated,  circular,  small, 
and  heavy  blood  disc. 

The  cell  of  the  first  period  is  therefore  spherical,  white,  and  nucleated ; 
that  of  the  second,  red,  disc-shaped,  and  nucleated ;  that  of  the  third,  red, 
disc-shaped,  bi-concave,  and  non-nucleated. 

The  primordial  cell  advances  in  development  to  different  points  in  dif- 
ferent orders  of  living  beings.  The  blood  of  invertebrated  Development 
animals  contains  coarse  granule  cells,  which  pass  forward  to  ^th^atiS 
the  condition  of  the  fine  granule  cells,  and  reach  the  utmost  series, 
perfection  they  are  there  to  attain  in  the  colorless  nucleated  cell  of  the 
first  period  of  man.  In  oviparous  vertebrated  animals  the  development 
is  carried  a  step  farther,  the  red  nucleated  cell  arising,  and  in  them  it 
stops  at  this,  the  second  period.  In  mammals  the  third  stage  is  reached 
in  the  red,  non-nucleated  disc,  which  is  therefore  the  most  perfect  form. 

This  perfect  form  of  blood  cell,  as  it  occurs  in  man,  may  be  described 
as  presenting  a  flattened  shape ;  the  bright  spot,  which  is  sometimes  seen 
in  the  centre,  arising  from  a  refraction  of  light  due  to  the  form  of  the 


116 


CIECULAR   AND   ELLIPTIC   CELLS. 


disc  and  not  to  a  nucleus.  The  sac  of  each  disc  is  elastic,  so  that  it  can 
Pro  erties  and  ^e  swo^en  ^7  water  until  it  becomes  convex  or  even  globu- 
sizeoftheper-  lar,  or  by  immersion  in  thick  sirup  may  be  made  to  shrink, 
:el  '  effects  arising  from  the  endosmotic  infiltration  or  exudation 
through  its  wall.  When  passing  through  the  fine  capillaries  in  the 
course  of  the  circulation,  the  cell,  by  reason  of  this  elasticity,  can  make 
its  way  through  very  difficult  passages,  extending  itself  into  a  cylindroid 
form,  or  by  bending,  but  it  recovers  its  original  shape  as  soon  as  relieved 
from  pressure.  The  average  diameter  of  the  cell  is  estimated  at  32*OQ  of 
Fig.  42.  an  incn»  the  extremes  being  ^J^,  and-^^i^. 

The  thickness  of  the  cell  is  about  -12400  of 
an  inch.  The  cell  owes  its  color  to  ha3ma- 
tin,  which  exists  in  its  interior  in  a  state  of 
solution,  and  associated  with  globulin. 

The  facts  mentioned  in  the  preceding  par- 
agraph are  illustrated  by  the  annexed  en- 
graved photographs.    Fig.  42  represents  hu- 
man blood-ceils.    Their  form  is  circular  :  they 
have  a  central  depression,  but  no  nucleus. 
Fig.  43  represents  the  elliptic  nucleated 
blood-cells  of  the  frog,  with  here  and  there, 
Fig.  44  represents  .the  endosmotic  action  of 


Human  blood-cells  magnified  500  diam 
eters. 


at  a  a,  chyle  corpuscles. 

Fig.  43. 


Fig.  44. 


Elliptic  blood-cells  of  frog  magnified  250  diame- 
ters. 


Action  of  vrater  on  elliptic  cells. 


water  on  these  cells.  Fig.  45,  the  action  of  acetic  acid  in  darkening  or 
concentrating  the  nucleus.  In  Fig.  46  we  have  an  illustration  of  the 
size  and  appearance  of  the  blood-cell  in  a  reptile,  the  photograph  from 
which  this  figure  was  taken  having  been  made  under  the  same  magni- 
fying power  as  that  employed  in  obtaining  the  photograph  of  human 
blood. 


FOEMS   OF  BLOOD-CELLS. 


117 


Fig.  45. 


Fig.  40. 


Action  of  acetic  acid  on  elliptic  cells. 


Reptile  blood-cells  magnified  500  diameters. 


The  mammals  in  which  the  blood  corpuscles  are  not  round,  but  ellip- 
tic and  bi-convex,  are  the  camel,  the  dromedary,  and  the  llama.  In 
birds  and  amphibia  they  are  oval.  The  difference  in  the  shape  and  size 
of  these  cells  is  of  the  more  importance,  since  observations  and  measure- 
ments by  the  microscope  may  lead  us  to  a  correct  reference  of  a  sample 
of  blood  to  its  origin  when  chemical  analysis  would  afford  us  no  assist- 
ance. It  is  not  to  be  forgotten,  however,  that  both  in  size  and  form  a 
blood-cell  undergoes  changes  according  to  unequal  pressures  Variations  Qf 
exerted  upon  it,  or  to  the  physical  circumstances  under  which  the  form  of 
it  is  placed,  liquid  readily  finding  its  way  into  its  interior  or  blo°  ills' 
exuding  therefrom  according  to  the  laws  of  endosmosis,  the  elastic  sac 
perfectly  accommodating  itself  to  these  changes.  As  a  consequence  of 
these  modifications,  there  will,  of  course,  follow  variations  of  specific  grav- 
ity in  the  cell,  differences  in  its  tendency  to  sink  in  the  plasma  which 
surrounds  it,  and  also  differences  in  its  tint  of  color. 

By  Mr.  Wharton  Jones,  the  colored  blood-disc  of  the  mammalian  is 
regarded  as  being  homologous  with  the  nucleus  of  the  color-  Human  blood 
less  corpuscle  of  the  same  blood,  and  it  may  therefore  be  disc  is  a  ceii^- 
spoken  of  as  a  free  cellseform  nucleus,  the  cell  itself  having  form  nucleus- 
deliquesced  or  become  disintegrated,  and  the  nucleus,  filled  with  globulin 
and  coloring  matter,  remaining. 

The  cell  wall  of  the  blood-cells  is  generally  admitted  to  be  fibrin,  or 
some  substance  allied  thereto  ;  but  there  has  been  much  dif-  Nature  of  the 
ference  of  opinion  respecting  the  constitution  of  the  nucleus  cell  walls  and 
of  those  cells  which  possess  it.  By  some,  this  also  has  been 
regarded  as  fibrin  ;  by  others,  as  fat  ;  and  by  others,  as  a  species  of  horn, 
to  which  the  designation  of  nucleine  has  been  given. 

The  cell  wall  of  the  white  corpuscles  does  not  appear  to  be  elastic. 
It  is  viscid,  and  hence  these  bodies,  tend  to  agglutinate  with  one  another  : 


118  COMPOSITION   OF   BLOOD-CELLS. 

in  aspect  it  is  granular.     The  contents  appear  to  be  an  albuminous  so- 
lution, in  which,  fine  granules  are' suspended. 

Though  we  have  described  the  mesenteric  glands  as  the  original  place 
of  formation  of  the  blood-cells,  it  is  to  be  understood  that 
these  become  perfected  in  the  circulation  of  the  blood ;  and 
from  what  will  be  said  respecting  the  function  of  the  liver,  it  may  be  in- 
ferred that  that  gland  is  the  seat  of  a  most  important  change  :  there 
probably  they  receive  their  iron.     That  no  special  organ  is  exclusively 
charged  with  the  duty  of  forming  them  appears  from  this,  that  the  first 
form  of  blood-cells  arises  in  the  germinal  area  of  the  embryo  when  there 
is,  as  yet,  no  gland. 

Composition  of  Blood-cells. 

Water 688.00 

Haematin  (including  iron) 16.75 

Globulin  and  cell  membrane 282.22 

Fat 2.31 

Extractive 2.60 

Mineral  substances 8.12 

1000.00 

Leaving  the  water  out  of  consideration,  the  predominating  ingredients 
of  blood-cells  are  therefore  globulin  and  ha3matin.  The  former  is  a  sub- 
stance approaching,  in  properties,  to  casein,  or  perhaps  intermediate  be- 
tween casein  and  albumen.  Its  constituents,  as  determined  by  an  ulti- 
mate analysis,  are  the  same  as  in  the  case  of  those  bodies. 

Ha3matin  is  distinguished  by  its  red  color.  When  isolated,  it  exhibits 
Changes  of  col-  the  changes  of  tint  characteristic  of  arterialization  in  a  doubt- 
or  depending  ful  manner.  There  are,  however,  many  facts  which  lead  to 
t^Cforn?oftne  the  supposition  that  the  color  of  arterial  and  venous  blood 
cells.  does  not  depend  so  much  on  a  chemical  change  in  the  ha3ma- 

tin  as  on  an  alteration  of  the  figure  of  the  discs. 

The  constitution  of  hasmatin  is  C44,  H22,  N3,  O6,  Fe.  It  exists  under 
Properties  of  two  forms,  soluble  and  coagulated.  It  has  hitherto  been  stud- 
hrcmatin.  }e(j  O11}y  in  the  latter  state,  and  is  soluble  in  weak  alcohol 
acidulated  with  sulphuric  or  hydrochloric  acid,  but  not  in  water.  Its 
solution  is  therefore  precipitated  by  the  addition  of  that  liquid.  In  weak 
solutions  of  alkalies  it  readily  dissolves.  Formerly  its  characteristic  red 
color  was  attributed  to  the  iron  it  contains,  but  that  metal  may  be  en- 
tirely removed  from  it  without  changing  its  tint.  The  amount  of  iron  it 
yields  is  about  seven  per  cent. 

Ha3matin  occurs  in  the  blood-cells  associated  with  globulin,  and  would 
seem  to  owe  its  origin  to  the  action  of  the  wall  of  the  cell,  if  it  be  true 
that  the  red  cells  originate  from  the  white  ones.  In  this  formation  of 
ha3matin  there  are  several  reasons  which  lead  us  to  infer  that  fat  takes 
an  essential  share. 


COMPOSITION   OF   REMATIN.  119 

Ultimate  Analysis  of  flcematin. 

Carbon C53.47 

Hydrogen 54.45 

Nitrogen 103.9G 

Oxygen 118.81 

Iron 69.31 

1000.00 

The  remarkable  feature  in  the  composition  of  this  "body  is  the  large 
quantity  of  iron  it  contains.  The  percentage  amount  of  this  iron  in  the 
metal  in  the  blood  of  the  foetus  is  much  greater  than  in  that  of  cells- 
the  mother.  After  birth  the  proportion  declines,  but  it  rises  again  at 
puberty.  These  variations  in  the  amount  of  the  iron  are,  however,  de- 
pendent on  corresponding  variations  in  the  amount  of  cells. 

The  importance  of  the  remark,  when  we  arrive  at  the  study  of  the 
bile,  justifies  us  in  repeating  that  the  iron  of  the  blood  belongs  to  the 
haematin  of  the  cells,  its  percentage  proportion  varying  with  their  condi- 
tion, and  also  with  the  region  of  the  circulation  from  which  they  have 
been  drawn.  As  derived  from  different  animals,  the  cells  present  differ- 
ent quantities  of  this  metal.  Thus  Schmidt  found  in  100  parts  of  dry 
blood-cells  in  man,  0.4348  ;  in  the  ox,  0.509  ;  in  the  pig,  0.448  ;  and  in 
the  hen,  0.329. 

The  crystalline  substance  of  blood  occurs  under  three  dmercnt  forms, 
in  prisms,  tetrahedra,  and  hexagonal  tablets.     In  the  pris-  Cr  stalline 
matic  form  it  is  derived  from  human  blood,  that  of  fishes,   substance  of 
and  of  some  mammals ;  in  the  tetrahedral  form  it  is  obtained  blood' 


Fin.  4i. 


Fig.  48. 


Human  bK>ou-c;-ystals. 


Blood-crystals  o:'  Guinea-pig. 


from  Guinea-pigs,  rats,  and  mice;  in  the  hexagonal' form,  from  squir- 
rels. Blood-crystals  are  of  a  red  color,  without  smell  or  taste,  losing 
their  water  of  crystallization  under  exposure  to  the  air,  the  different  forms 
presenting  different  rates  of  solubility ;  the  tetrahedral  being  soluble 


120 


BLOOD-CRYSTALS. 


in  600  parts  of  water,  the  prismatic 
in  90  parts  only;  the  solution  in 
the  former  case  being  pinkish,  that 
of  the  latter,  dark  red.  They  are 
also  dissolved  by  acetic  acid,  the  red 
prussiate  of  potash  producing  a  pre- 
cipitate therefrom,  as  in  the  case  of 
^  other  protein  bodies.  Chlorine  de- 
colorizes their  solutions  and  gives  a 
white  flaky  precipitate.  The  crys- 
tals, when  heated,  swell,  yield  an 
odor  like  burnt  horn,  and,  after  com- 
bustion, leave  a  small  quantity  of 
Biood-crystais  of  squirrel.  ash.  From  the  difficulty  of  obtain- 

ing blood-crystals  in  a  state  of  purity,  their  constitution  is  not  known 
with  absolute  certainty.  The  ash  which  they  yield  consists  of  about  72 
per  cent,  of  oxide  of  iron,  and  21  per  cent,  of  phosphoric  acid,  the  protein 
constituent  being  apparently  identical  with  other  protein  bodies.  The 
Mode  of  ob-  crystals  may  be  obtained  for  examination  by  covering  a  mi- 
taining  blood-  nute  drop  of  blood  with  a  glass  slide,  and,  after  adding  water, 
alcohol,  or  ether,  to  permit  a  gradual  evaporation  to  ensue. 
The  amount  thus  produced  depends  very  much  upon  the  presence  of  light; 
thus  Lehmann  found  that  while  he  could  only  obtain  two  per  cent,  of 
crystals  from  the  blood  of  the  Guinea-pig  in  the  dark,  he  could  obtain 
more  than  seven  per  cent,  in  the  sunlight. 

Lehmann  believes  that  the  crystalline  substance  is  not  a  mixture  of  a 
pigment  and  a  protein  body,  but  a  pure  chemical  compound,  having  either 
a  salt-like  or  conjugated  constitution. 

The  color  of  the  blood,  as  dependent  upon  the  tint  of  its  cells,  is,  ac- 
Coior  of  blood-  cording  to  the  views  of  Henle,  connected  to  a  considerable 
degree  with  the  form  of  those  organisms  as  they  vary  from  a 
concave  to  a  convex  surface,  and  not  with  the  state  of  the 
hsematin.  When  they  are  more  concave  they  are  of  a  crimson,  when 
of  a  more  convex,  of  a  darker  hue.  Moreover,  during  these  variations 
their  investing  membrane  must  necessarily  change  in  thickness,  and  this 
likewise  must  alter  their  mode  of  transmitting  light. 

Among  the  causes  which  can  impress  a  change  on  the  figure  of  the 
blood-cells  ought  particularly  to  be  specified  exposure  to  oxygen  and 
carbonic  acid  respectively,  the  latter  causing  them  to  become  more  opaque 
in  their  centre,  broader  upon  their  edge,  the  cell  distending ;  an  opposite 
effect  ensuing  under  exposure  to  the  former.  In  the  case  of  the  blood- 
cells  of  frogs  exposed  to  oxygen,  the  long  and  short  diameters  both  di- 
minish, and  the  wall  becomes  granular ;  after  exposure  to  carbonic  acid 
they  increase,  the  wall  becoming  pellucid. 


cells  may  de- 
pend on  their 
form. 


NUMBER   OF  BLOOD-CELLS.  121 

Constituted  thus  of  an  elastic  sac  filled  with  globulin  and  hsematin,  the 
cells  float  in  the  plasma.  They  are  nourished  at  its  expense,  and  when 
they  die,  deliver  up  their  contents  Iby  deliquescence  to  it.  Accompany- 
ing them  are  the  white  corpuscles,  from  which  new  generations  are  to 
arise.  It  is  usually  stated  that  for  every  50  red  discs  there  The  white 
is  one  white  corpuscle.  They  may  be  readily  discovered  dur-  corPuscles- 
ing  the  circulation  by  the  microscope,  many  of  them  occupying  the  exte- 
rior of  the  current,  as  though  they  had  a  special  relation  to  the  soft  tis- 
sues. It  may  perhaps  be  erroneous  to  regard  these  large  white  corpus- 
cles as  the  embryos  of  the  red  discs.  Reasons  could  be  assigned  in  sup- 
port of  the  doctrine  that  the  same  primitive  germ  going  onward  to  devel- 
opment may,  at  a  certain  point,  diverge  in  two  directions ;  if  it  passes 
through  one,  it  will  perfect  itself  as  a  white  cell;  if  through  the  other,  as  a 
red  disc. 

The  proportional  number  of  blood  corpuscles  in  different  animals  va- 
ries considerably.  Generally  cold-blooded  mammals  present  Number  of  cells 
fewer  than  warm-blooded  ones,  birds  having  more  than  quad- 
rupeds,  and  among  these  the  carnivora  more  than  the  herbiv- 
ora.  Of  different  domestic  animals,  the  pig,  the  dog,  the  ox,  the  horse, 
the  cat,  the  sheep,  the  goat,  possess  them  in  the  order  in  which  their 
names  have  been  mentioned,  the  goat  having  only  86  to  145  in  the  pig. 
Their  proportional  number  also  varies  in  different  regions  of  the  circula- 
tion ;  thus  it  is  said  that  arterial  blood  contains  fewer  than  venous,  the 
portal  blood  fewer  than  the  jugular,  the  hepatic  more  than  the  portal.  It 
is  not,  however,  to  be  overlooked,  that  in  all  these  determinations  the 
quantity  of  water  which  chances  to  be  present  controls  the  estimates,  and 
that  therefore,  as  thus  offered,  they  are  really  of  less  interest  than  might 
at  first  sight  be  supposed. 

We  have  next  to  speak  of  the  plasma.     It  may  be  described  as  a  clear 
and  slightly  yellowish  colored  fluid,  consisting,  as  all  animal  composition 
juices  do,  for  the  most  part  of  water,  holding  in  suspension  or  of  plasma, 
solution  albumen,  fibrin,  fats,  and  various  mineral  bodies,  as  the  follow- 
ing analysis  shows. 

Proximate  Composition  of  the  Plasma. 

Water 902.90 

Albumen 78.84 

Fibrin 4.05 

Fat 1.72 

Extractive 3.94 

Mineral  substances 8.55 

1000.00 

Of  the  water  it  may  be  remarked,  that  the  usual  percent-  Water  of  the 
age  estimate  made  of  its  quantity,  as  regards  the  entire  blood,  whole  blood : 
is  from  700  to  790  parts  in  1000.  Within  these  limits  it  is  its  variations- 


122  VARIATIONS   IN   WATER,  ALBUMEN,  AND   FIBRIN. 

liable  to  rapid  variations,  as  dependent  on  the  condition  of  thirst  or  the 
recent  indulgence  in  drinks.  It  does  not  increase  in  proportion  to  the 
amount  which  has  been  imbibed,  for  the  Malpighian  bodies  of  the  kidney, 
as  will  hereafter  appear,  strain  it  off  with  great  rapidity.  When  the 
blood-vessels  are  distended  to  a  certain  degree,  they  refuse  an  entrance  to 
it.  The  necessity  of  these  provisions  arises  from  the  fact  that  there  is  a 
certain  state  of  viscidity  which  the  blood  must  possess  for  its  proper  cir- 
culation. 

Eespecting  variations  in  the  amount  of  water  in  the  blood,  it  may  be 
stated  that  that  of  women  contains  more  water  than  that  of  men.  Among 
different  animals,  the  serum  of  the  amphibia  contains  the  largest  quantity; 
and  among  mammals,  that  of  the  herbivora  more  than  that  of  the  car- 
nivora.  Obtained  from  different  vessels,  the  arterial  has  more  than 
venous  blood,  but  the  serum  of  the  portal  vein  contains  more  than  that 
of  any  other  vein,  the  proportion  depending  on  the  amount  and  time  of 
the  ingestion  of  water. 

The  albumen  varies  in  quantity  from  60  to  70  in  1000.  It  is  prob- 
Variations  in  a^v  associated  or  combined  with  soda.  It  exists  in  the 
quantity  of  ai-  blood  of  the  splenic  and  hepatic  veins  as  the  neutral  albumi- 
nate  of  soda.  It  does  not  appear  to  contain  any  phosphorus, 
as  was  at  one  time  supposed.  It  is  the  plastic  material  from  which  all 
the  soft  tissues  are  nourished,  and  by  it  the  cells  themselves  grow. 
Fibrin  arises  from  it  in  the  blood  in  the  same  manner  as  it  does  during 
the  incubation  of  an  egg ;  every  care  is  taken  to  economize  it  in  the  sys- 
tem, and  it  is  never  excreted  except  in  disease. 

The  quantity  of  albumen  is  greater  in  venous  than  in  arterial  blood, 
the  proportion  increasing  during  digestion.  It  also  presents  variations 
in  different  states  of  disease.  Its  condition  varies  in  various  parts  of  the 
circulation,  a  circumstance,  to  a  considerable  extent,  due  to  the  nature  of 
the  salts,  or  to  the  quantities  of  alkali  with  which  it  is  associated. 

The  fibrin  is  usually  estimated  at  2  or  3  parts  in  1000  of  blood.     It 

Vari  tions  in  mav  ^1  as  ^ow  as  ^  or  r^se  as  high  as  7  j.  There  is  a  con- 
the  quantity  of  stant  drain  upon  it  for  the  nutrition  of  the  muscular  tissues ; 
and  since  it  originates  in  the  action  of  oxygen  upon  albu- 
men, we  should  expect,  as  is  really  the  case,  that  arterial  blood  would  be 
richer  in  it  than  venous.  The  portal  blood  contains  it  in  minimum  quan- 
tity. Its  percentage  rises  if  oxygen  be  inhaled,  or  the  respiratory  pro- 
cess be  quickened ;  for  similar  reasons,  it  uniformly  increases  in  acute 
inflammations.  The  ultimate  analyses  of  fibrin  seem  to  show  that  it  con- 
tains more  oxygen  than  albumen,  and  this  corresponds  with  its  mode  of 
origin.  It  is  an  important  practical  observation,  that  though  it  is  easy 
to  regulate  the  quantity  of  cells  by  variations  of  diet,  the  amount  of 
fibrin  can  not  so  readily  be  changed  in  that  manner,  nor  its  development 


FIBKIN,  FAT,  AND  SUGAR  OF  BLOOD.  123 

checked  by  venesection.     There  is  less  fibrin  in  the  blood  of  the  camiv- 
ora  than  in  that  of  the  herbivora. 

It  has  been  asserted,  as  was  mentioned  before,  that  there  is  so  wide  a 
difference  between  the  fibrin  of  blood  and  muscular  fibre,  Fibrin  is  a  his- 
that  we  can  no  longer  regard  the  latter  as  arising  from  the  togeneticbody. 
former,  but  must  consider  it  merely  as  coagulated  albumen ;  and  that, 
since  the  action  of  acetic  acid  upon  it  shows  its  relation  to  gelatine,  it  is 
probably  more  nearly  related  to  the  fibro-gelatinous  than  to  the  cellulo- 
albuminous  tissues.  But,  although  the  fact  that  fibrin  contains  more 
oxygen  than  albumen  seems  to  lend  weight  to  such  views,  since  oxida- 
tion appertains  to  the  retrograde  rather  than  to  the  ascending  metamor- 
phosis, there  are  so  many  arguments  in  favor  of  the  old  doctrine,  that 
I  think  it  may  be  regarded  as  thus  far  unshaken.  Moreover,  it  is  now 
established  beyond  any  doubt,  that  by  nitrate  of  potash,  and  other  salts, 
fibrin  may  be  transmuted  into  a  substance  analogous  to  albumen. 

The  fats  vary  very  much  in  quantity  at  different  times.     The  amount 
is  usually  stated  at  from  1.4  to  3.3  in  1000  of  blood.     After  a  meal  the 
plasma  may  be  actually  milky,  through  the  fat  globules  yariationsin 
brought  in  by  the  chyle.     We  have  already  shown  that  the  quantity  of 
starch  will  give  origin  to  fat,  and  oily  substances  can  be  ob-    at' 
tained  from  lactic  acid  itself.     The  nitrogenized  bodies,  during  their  de- 
struction, likewise  yield  them,  and  it  is  a  normal  function  of  the  liver  to 
effect  the  production  of  fat. 

The  serum  contains  only  an  insignificant  quantity  of  free  fat ;  but 
there  is  a  large  proportion  of  saponified  fat  in  it,  as  well  as  the  lipoids 
cholesterine  and  serolin. 

The  view  heretofore  taken,  that  this  class  of  substances  is  not  histo- 
genetic,  but  only  respiratory,  requires  to  be  modified.  There  Uses  of  the  fats 
is  reason  to  believe  that  the  blood-cells  themselves  can  not  of  blood- 
be  formed  except  in  presence  of  oil,  which  is  also  necessary  to  enable  ni- 
trogenized bodies  to  assume  the  ferment  action.  The  nuclei  of  cells  con- 
tain fats,  as  do  also  embryonic  structures  generally.  Cholesterine,  or 
liver-fat,  is  not  saponifiable.  It  appears  as  a  product  of  disintegration, 
increasing  in  quantity  during  acute  diseases.  The  proportion  of  this  sub- 
stance increases  after  40  years ;  it  also  forms  a  principal  ingredient  in 
biliary  concretions. 

Among  the  special  constituents  of  certain  portions  of  the  venous  blood 
not  mentioned  in  the  preceding  tables,  we  ought  not  to  over- 

,.,          .      •  .  T?  ,*I-I-IT    Liver-sugar. 

look  sugar,  which  exists  as  a  constant  ingredient  of  the  blood 
contained  in  that  part  of  the  circulation  intervening  between  the  liver  and  . 
the  lungs.     This,  which  is  known  as  liver-sugar,  may  have  originated  in 
the  transmutation  of  cane-sugar,  or  from  the  metamorphosis  of  the  mus- 
cular tissues.     It  is  to  be  remarked  that  the  blood  contains  no  gelatine. 


124 


THE   MINERAL   CONSTITUENTS  OF  BLOOD. 


Comparison  of  To  the  mineral  substances  in  the  cells  and  plasma  of  the 
constituents  of  Wood  respectively,  attention  should  be  particularly  directed, 
the  cells  and  smce  they  indicate  the  functions  of  these  portions. 

plasma. 

Mineral  Constituents  in  1000  Parts  of  the  Blood. 


(Jells. 

Plasma. 

Chlorine 

1  686 

0   (\AA 

Sulphuric  acid  

0  066 

O-I-IK 

Phosphoric  acid 

1  134 

0101 

Potassium  

3  328 

0  39°$ 

Sodium                 

1  052 

q  041 

Oxvcren  . 

0  667 

0  4-03 

Phosphate  of  lime 

0  114 

n  qi  i 

Phosphate  of  magnesia  

0  073 

0  222 

Iron  excluded  

****** 

8.120 

8.550 

The  amount  of  inorganic  matter  in  the  cells  and  plasma,  respectively, 
of  1000  parts  of  blood  being  nearly  the  same,  the  table  shows  that  there 
is  more  than  twice  as  much  chlorine,  and  more  than  three  times  as  much 
sodium  in  the  plasma  as  in  the  cells.  It  may  thence  be  inferred  that  the 
chloride  of  sodium  is,  for  the  most  part,  in  the  plasma.  Moreover,  there 
is  six  times  as  much  phosphorus,  and  more  than  ten  times  as  much  po- 
tassium, in  the  cells  as  in  the  plasma ;  and  therefore  it  may  be  inferred, 
since  potash  is  required  to  so  great  an  extent  in  the  nutrition  of  the  mus- 
cular system,  and  phosphorus  as  an  element  of  the  phosphorized  oils  in 
the  nervous,  that  the  cells  have  a  direct  functional  relation  to  those  im- 
portant mechanisms,  and  this  in  addition  to  their  duty  of  introducing 
oxygen. 

The  mineral  constituents  of  the  blood  discharge  very  different  duties, 
Functions  of  some,  either  directly  or  indirectly,  acting  functionally,  others 
consTituenfsof  as  histogenetic  bodies.  Thus  the  alkaline  properties  of  the 
the  blood.  blood  are  due  to  the  presence  of  the  carbonate  and  phosphate 
of  soda,  and  this  latter  substance  enables  the  serum  to  hold  in  solution 
carbonic  acid,  and  thus  it  maintains  a  relation  in  the  respiratory  opera- 
tion. But  the  phosphate  of  lime  discharges  a  true  histogenetic  function, 
since  upon  it  the  bony  system  depends  for  its  nutrition.  The  mutual 
relations  of  these  substances  are,  of  course,  very  complex,  though  often 
of  importance.  Thus,  of  the  two  just  mentioned,  the  phosphate  of  soda 
enables  the  serum  to  hold  the  phosphate  of  lime  in  solution. 

The  tawny  coloring  matter  of  serum  diifers  from  cholepyrrhin  in  not 
Coloring  mat-  yielding  the  characteristic  reaction  of  that  body.  The  tint 
ter  of  serum,  sometimes  becomes  quite  deep,  owing  to  several  different 
.causes,  such  as  the  undue  accumulation  of  the  coloring  matter  of  urine, 
through  disturbance  of  renal  action,  or  from  bile  pigment,  as  in  icterus. 

The  gases  which  can  be  disengaged  from  the  blood  occur  in  the  cells, 
according  to  Magnus,  a  statement  which,  however,  is  very  far  from  being 


FUNCTIONS   OF   THE   CONSTITUENTS   OF   BLOOD.  125 

substantiated :  they  are  carbonic  acid,  oxygen,  and  nitrogen.  Gases  of  the 
He  found  that  this  liquid  can  absorb  once  and  a  half  its  vol-  blood- 
ume  of  carbonic  acid,  and  that  in  arterial  blood  the  proportion  of  that 
acid  to  oxygen  is  as  16  to  6,  in  venous  as  16  to  4.  That  the  oxygen 
is  very  loosely  retained  is  shown  by  the  circumstance  that  it  may  for 
the  most  part  be  removed  by  exposure  in  a  vacuum.  The  other  gases 
may  be  withdrawn  by  a  stream  of  hydrogen. 

At  a  temperature  of  98°,  water  absorbs  scarcely  one  per  cent,  of  its 
volume  of  oxygen  gas,  but  the  blood  can  take  up  from  10  to  13  times  as 
much.  This  is  accomplished  by  the  coloring  material.  The  amount  is 
independent  of  variations  in  the  pressure  of  the  air,  which  would  not  be 
the  case  if  the  gas  were  received  into  the  circulating  fluid  by  mere  solu- 
tion. This  is  the  opinion  of  Liebig,  by  whom  it  is  regarded  as  being  to 
some  extent  substantiated  by  the  fact  that  the  respiration  is  accomplished 
with  nearly  the  same  result,  so  far  as  the  absorption  of  oxygen  is  con- 
cerned, at  considerable  heights  above  and  at  the  level  of  the  sea,  and  that 
no  more  oxygen  is  received  from  an  atmosphere  very  rich  in  that  gas 
than  from  the  ordinary  air.  However  correct  this  view  may  be,  the  facts 
cited  in  its  support  are  very  far  from  being  undeniable. 

The  preceding  chemical  examination  of  the  special  constituents  of  the 
blood  leads  us  next  to  consider  the  general  functions  of  this  liquid  in  the 
aggregate. 

In  this  general  sense,  the  blood  discharges  the  following  offices.     Its 
albumen  has  the  duty  of  giving  origin  to  all  the  plastic  tis-  General  state 
sues  of  the  system.     From  it,  for  example,  by  cell  action,  as  ment  of  the 
explained  in  treating  of  lacteal  absorption,  fibrin  arises —  theliiffkrent 
fibrin,  which  is  used  for  the  renovation  and  repair  of  the  mus-  constituents  of 
cular  tissues.    The  discs  have  a  relation  with  the  function  of 
respiration;  they  obtain  oxygen  in  the  pulmonary  circulation,  and  carry 
it  through  the  system.     They  contribute,  moreover,  to  the  development 
of  muscular  fibre,  and  also  nervous  material,  and  this  not  alone  as  regards 
the  coloring  matter  of  those  tissues.     The  fats  are  necessary  in  the  pro- 
duction of  fibrin  and  for  the  nuclei  of  cells ;  but,  besides  these  histoge- 
netic  relations,  they  eventually,  with  the  exception  of  liver-fat,  undergo 
oxidation,  and  so  minister  to  the  support  of  a  high  temperature.     Of  the^ 
saline  substances,  common  salt  promotes  digestion  by  aiding  in  the  prep- 
aration of  gastric  and  pancreatic  juices ;  the  phosphate  of  soda  enables 
the  plasma  to  hold  carbonic  acid  in  solution,  and  carry  it  to  the  lungs. 

It  is  interesting  to  observe  the  limits  of  variation  which  the  blood  may 
present  in  disturbed  or  diseased  conditions.  In  inflammations,  the  fibrin 
may  increase  fourfold ;  in  typhoid  fevers  it  may  diminish  to  less  than 
one  half,  and  from  these  variations  special  results  may  arise.  Thus 
diminution  of  its  fibrin  disposes  the  blood  to  preternatural  oozing  or  fa- 


126  CHANGES   IN   THE   CIRCULATION. 

cility  of  escape.  So  also  the  cells  have  been  known,  in  cases  of  chloro- 
sis, to  sink  to  one  fifth  of  the  healthy  amount.  The  albumen,  too,  ex- 
hibits like  variations.  In  Bright's  disease  it  greatly  diminishes,  much 
of  it  escaping  in  the  urine  by  the  straining  action  of  the  kidneys. 

Thus  constituted,  the  blood,  by  a  mechanism  to  be  described  in  the 
Chan  es  occur  next  cnaPter»  passes  from  the  heart  alternately  to  all  parts 
ring  during  the  of  the  system,  and  alternately  to  the  cells  of  the  lungs,  giv- 
circuiation.  -^  T^Q  ^Q  what  have  been  termed  the  greater  and  less  cir- 
culation, or  the  systemic  and  the  pulmonary.  In  the  systemic  circula- 
tion, the  blood,  which  leaves  the  heart  in  an  arterialized  condition,  or  as- 
sociated with  atmospheric  oxygen,  gives  up  that  element  to  the  various 
tissues  as  it  pervades  them,  and  accomplishes  a  double  result:  the  re- 
moval of  all  those  particles  which,  having  discharged  their  duty  and  un- 
dergone partial  or  perfect  interstitial  death,  are  ready  to  pass  away,  and 
also  the  liberation  of  a  great  amount  of  heat  by  the  destructive  oxidation ; 
so,  at  the  same  time,  the  wasted  matter  is  removed  and  advantage  taken 
of  it  to  raise  the  temperature  of  the  body.  This  done,  the  blood  makes 
its  way  back  to  the  heart,  following  the  channel  of  the  veins  as  they  suc- 
cessively converge  into  trunks  that  are  larger  and  larger.  At  the  mo- 
ment of  surrendering  its  oxygen  and  receiving  the  various  products  of 
combustion,  a  change  of  color  occursr  The  bright  crimson  turns  to  a 
deep  blue,  and  the  blood  presents  itself  of  that  color  at  the  heart. 

It  now  undergoes  the  less  or  pulmonary  circulation.  Leaving  the 
heart,  it  passes  over  the  air-cells  of  the  lungs,  and  is  there  exposed  to  the 
aerating  action  of  the  atmosphere.  From  the  interior  of  the  cells  the 
discs  receive  their  supply  of  oxygen,  the  plasma  surrendering  up  carbonic 
acid  and  the  vapor  of  water.  The  color  now  changes  back  from  the 
blue  to  the  scarlet.  In  this  condition  it  returns  to  the  heart,  to  be  dis- 
tributed in  the  systemic  circulation  once  more. 

During  this  double  round  an  incessant  change  is  taking  place  in  the 
Less  obvious  constitution  of  the'blood:  it  is  undergoing  a  continuous  met- 
but  important  amorphosis.  In  some  respects,  as,  for  instance,  in  color, 
this  is  obvious  enough.  But  the  invisible  changes  infinite- 
ly exceed  in  importance  and  amount  those  that  are  obvious  to  the  eye. 

All  the  soft  tissues,  since  they  are  wasting  away,  require  repair. 
This,  inasmuch  as  it  is  accomplished  either  directly  or  indirectly  by  the 
albumen  of  the  blood,  gives  rise  to  a  constant  drain  of  that  substance, 
and  demands  a  constant  supply,  which  is  provided  by  nutrition  or  stom- 
ach digestion. 

The  cells,  which  constitute  the  other  chief  portions  of  the  blood,  are 
Translation  of  necessaiT  *°  tne  production  of  a  high  temperature,  by  con- 
oxygen  by  th«  stantly  transferring  oxygen  from  the  cells  of  the  lungs  to 
cells.  every  part  of  the  body ;  carriers  of  oxygen  they  have  been 


GRADUAL  DESTRUCTION  OP   BLOOD-CELLS.  127 

truly  called.  That  this  is  one  of  their  duties  has  been  proved  experi- 
mentally, for  a  solution  of  albumen  or  the  serum  has  but  little  power  of 
absorbing  oxygen,  scarcely  exceeding  water  itself  in  that  respect,  but 
the  discs  condense  it  at  once.  The  change  of  color  they  exhibit  as  they 
alternately  gain  or  lose  that  element,  is  in  itself  a  proof  of  this  fact,  as 
is  also  the  action  of  serum  or  blood-discs  respectively  on  a  measured 
volume  of  air  contained  in  a  jar.  If  the  discs  be  in  the  venous  or  pur- 
ple condition,  they  quickly  absorb  oxygen  from  the  confined  air,  which 
therefore  at  once  diminishes  in  amount,  but  the  serum,  or  a  solution  of 
albumen,  produces  no  such  effect.  The  plasma  serves,  therefore,  for  the 
general  nutrition  of  the  system,  and  the  discs,  by  transferring  oxygen 
from  point  to  point,  discharge  that  part  of  their  duty  which  is  connect- 
ed with  the  production  of  heat. 

But  the  discs,  though  of  a  flattened  form,  are  truly  cells,  and  all  that 
obtains  in  the  case  of  cell  life  and  cell  action  obtains  for  „, 

Transitory  du- 

them.     They  have  not  a  duration  at  all  comparable  to  the  ration  of  the 
duration  of  the  system,  but  are  constantly  coming  into  ex-  cells*    • 
istence  and  disappearing.     Each  is  an  individual  having  its  own  partic- 
ular history,  its  time  of  birth,  its  time  of  maturity,  its  time  of  death. 
Each  passes  through  a  series  of  incidents  proper  to  itself.     Originating 
as  has  been  described,  they  grow  at  the  expense  of  the  plasma,  and  in 
this  regard  it  serves  for  their  nutrition  as  well  as  for  that  of  the  body 
generally. 

On  exposing  blood-cells  to  oxygen  and  carbonic  acid  gases  alternately, 
there  is  not  only  a  change  in  their  shape,  which  becomes  corrugated  and 
star-like,  but  also  in  their  chemical  constitution,  so  that,  after  such  an 
exposure  of  nine  or  ten  times,  they  are  entirely  destroyed.  Such  alter- 
nations occurring  in  the  system  doubtless  lead  to  the  same  result,  though 
more  slowly,  since  the  oxygen  is  presented  in  a  diluted  condition. 

The  corrugated  and  star-like  blood-cells  abound  in  the  blood  of  the 
portal,  though  not  in  that  of  the  hepatic  vein.     If  their  aspect 
arises  from  their  tendency  to  disintegration,  this  is  no  more      ym 

than  might  be  expected  in  view  of  the  func- 
tions of  the  liver.  That  the  stellated  aspect 
is  an  indication  of  a  commencing  disorganiza- 
tion, or  other  profound  change,  may  be  illus- 
trated by  an  examination  of  the  action  of  wa- 
ter on  normal  blood-cells,  which,  if  they  be 
exposed  to  that  liquid,  undergo  a  distention  ; 
their  thicknels  increasing  more  rapidly  than 
their  diameter,  they  lose  their  concavity,  be- 
come convex,  and  at  last  appear  as  spheres 


Stellated  blollsagnified  500       Qf  fl  ^  ^  thaR  ^  original  <Jiscs. 


128  ASSOCIATION  OF  H^MATIN   AND  OXYGEN. 

the  quantity  of  water  they  have  received  has  distended  them  to  their  ut- 
most capacity,  they  then  are  invisible ;  but  when  it  is  withdrawn  from 
them  by  establishing  exosmosis  through  the  addition  of  saline  sub- 
stances, they  may  reappear  in  the  corrugated  or  star  shape,  as  seen  in 
the  photograph,  Fig.  50. 

With  respect  to  the  action  of  the  hsematin,  it  may  be  observed,  that 
Action  of  hsem  ot^ier  nitrogenized  coloring  materials  present  a  similar  rela- 
atin  illustrated  tion  to  oxygen.  As  an  example,  indigo  may  be  mentioned, 
by  mdigo.  j  cons^er  that  the  properties  of  this  substance  illustrate  in 
a  significant  manner  the  properties  of  hasmatin  in  the  system.  Indigo 
occurs  in  the  leaves  of  the  plant  which  yields  it  in  a  yellow  and  soluble 
state.  It  is  easily  extracted  from  them  by  maceration  in  water.  Ex- 
posed to  the  air,  it  absorbs  oxygen,  becomes  insoluble,  and  simultane- 
ously, gains  a  deep  blue  tint.  So  lightly  is  the  oxygen  thus  united  to 
it,  that  by  exposure  to  very  feeble  agents  it  surrenders  it  up,  and  repasses 
into  the  yellow  and  soluble  condition.  Once  more  exposed  to  the  air, 
it  turns  blue,  and  once  more  may  have  that  color  removed  from  it  by  tak- 
ing its  oxygen  away.  For  many  times  in  succession  its  tint  may  be 
thus  changed,  and  made  yellow  or  blue  at  pleasure. 

From  this  we  perceive  in  what  a  loose  manner  oxygen  is  held  by  such 
a  coloring  material ;  how  readily  it  surrenders  it,  and  how  readily  it  re- 
covers it.  Such  a  union  can  scarcely  be  called  an  oxidation  or  a  com- 
bination ;  it  is  rather  an  association. 

All  this  is  precisely  what  occurs  in  the  case  of  hasmatin.  It  takes  up 
Feeble  union  of  Ox7gen  w^n  rapidity  as  it  goes  over  the  cells  of  the  lungs, 
oxygen  and  and  turns  scarlet ;  it  surrenders  that  oxygen  with  equal  fa- 
cility as  it  passes  the  systemic  capillaries,  and  turns  blue. 
This  change  of  color  is  incessantly  taking  place ;  it  is  now  red,  and  now 
blue,  as  the  cells  are  passing  in  the  greater  and  the  less  circulation. 

Formerly  it  was  supposed  that,  in  the  act  of  respiration,  oxygen  from 
Eeception  and  the  air  united  with  carbon  of  the  blood  or  of  the  cells,  and 
ofTx^genty  carkonic  acid  formed,  a  combination  or  perfect  oxidation 
the  blood-cells,  taking  place  in  the  lung.  But, ,  if  this  were  true,  the  tem- 
perature of  those  organs  should  be  higher  than  that  of  the  rest  of  the 
body,  and  this  is  by  all  admitted  not  to  be  the  case. 

The  cells  are  therefore  carriers  of  oxygen.  They  receive  that  vivify- 
ing principle  as  they  move  over  the  respiratory  cells,  and,  freighted  with 
it,  pass  to  all  parts  of  the  body,  not  united  with  it,  nor  disorganized,  nor 
burnt  up  by  it,  but  holding  it  loosely,  and  ready  to  give  it  up  and  go 
back  again  for  a  fresh  supply.  * 

The  sac  containing  the  haematin  offers  no  kind  of  resistance  to  these 
exchanges.  It  will  be  fully  demonstrated  in  the  chapter  on  respiration 
that  this  is  the  case.  Thick  pieces  of  India-rubber,  stout  animal  mem- 


CIRCULATION   OF  THE   BLOOD.  129 

branes,  or  even  masses  of  stucco,  present  no  obstacle  to  the  passage  of 
gases.  The  delicate  wall  of  these  cells,  a  tissue  of  almost  inconceivable 
tenuity,  can  offer  no  resistance.  The  gas  passes  in  and  out  without  im- 
pediment or  restraint. 

But  though  in  this  manner  these  little  organisms  perform  their  duty, 
it  is  only  for  a  time.  They  may  take  oxygen  from  the  air-  Summar  of 
cells  and  give  it  up  in  the  system,  and  do  this  perhaps  many  the  function  of 
thousand  times,  but  it  comes  to  an  end  at  last.  The  inces-  b 
sant  motion  stops,  and  the  worn  and  exhausted  disc  is  brought  to  its  term. 
By  degrees,  as  old  age  steals  over  it,  it  becomes  corrugated  and  relaxed, 
is  unable  to  withstand  chemical  reagents,  as  its  younger  comrades  can 
do.  Through  the  microscope  it  seems  puckered  and  attenuated.  The 
red  color  of  its  interior  deteriorates  into  a  tawny  tint.  As  with  a  leaf  in 
the  autumn,  the  natural  color  of  which  disappears,  and  yellowness  or 
other  change  precedes  its  fall,  so  with  the  dying  disc.  Unable  any 
longer  to  discharge  its  duties,  its  existence  is  brought  to  a  close,  the  de- 
cayed ha^matin  is  shed  out  to  give  a  transient  tawny  tint  to  the  plasma, 
but  is  presently  strained  off  as  one  of  the  constituents  of  bile  by  the  liver. 
Nor  is  the  illustration  here  used  wholly  metaphorical,  for,  in  the  case  of 
herbivorous  animals,  Berzelius  has  shown  that  the  coloring  matter  of  their 
bile  is  identical  with  chlorophyll,  the  coloring  matter  of  leaves. 


CHAPTER  VIII. 

OF  THE  CIRCULATION  OF  THE  BLOOD. 

The  Heart  as  a  Machine. — Inadequacy  of  Harvey's  doctrine  of  the  Circulation. — Physical  Prin- 
ciple of  the  Circulation ;  applied  in  the  case  of  a  Nucleated  Cell,  Pervious  Tissue,  Motion  of 
Sap  and  of  Blood.  —  Dependence  of  the  Circulation  on  Respiration.  — Forms  of  Circulation  : 
Systemic,  Pulmonary,  Portal. — Description  of  the  Heart :  its  Movements. —  Their  Force,  Num- 
ber, and  Value. — Sounds  of  the  Heart. —  Cause  of  its  Contractions. — Description  of  the  Arte- 
ries, Capillaries,  Veins. — Explanation  of  the  Circulation  of  the  Blood. — Facts  supporting  it. — 
The  First  Breath. 

No  function  of  the  animal  mechanism  illustrates  more  strikingly  the 
doctrine  that  we  must  rely  on  physical  agents  for  physiological  explana- 
tions than  that  which  we  have  now  to  consider,  the  circulation  of  the 
blood. 

We  surrender  some  of  the  most  beautiful  recollections  of  classical 
mythology,  and  some  of  the  most  cherished  popular  illusions  The  heart  as 
of  our  own  times.     The  heart,  which  in  the  higher  classes  of  an  ensine- 
life  is  the  central  organ  of  impulse  of  the  circulation,  is  to  be  degraded 
into  a  mere  engine.     We  have  to  speak  of  its  valves,  its  cords,  its  pipes. 

I 


130  CIRCULATION   OF   THE   BLOOD. 

We  have  to  consider  its  exhausting  and  its  forcing  action — to  deal  with 
it  just  as  we  should  deal  with  any  hydraulic  apparatus.  In  the  old 
times  this  organ  was  looked  upon  as  the  seat  of  the  thoughts  and  the 
passions  ;  it  was  the  centre  of  all  good  and  evil,  purity  and  uncleanness, 
devotion  and  love.  In  the  modern  system  the  brain  has  succeeded  to 
the  functions  which  were  once  imputed  to  it. 

The  heart,  then,  is  no  longer,  an  altar  on  which  flames  are  burning,  no 
longer  the  seat  of  the  passions  and  the  source  of  love.  It  is  a  machine, 
but  what  kind  of  a  machine  ?  How  great  is  the  admiration  we  may  ex- 
press at  its  exquisite  construction !  This  little  organ  can  execute  three 
thousand  millions  of  beats  without  a  stop !  In  the  course  of  a  life,  such 
as  we  sometimes  meet  with,  it  has  propelled  half  a  million  tons  of  blood, 
and,  though  momentarily  wasting,  has  repaired  its  own  waste  all  the  time. 
The  mathematical  rhythm  of  its  four  moving  cavities,  the  perfect  closure 
of  its  mitral  and  semilunar  valves,  and  the  regurgitating  play  of  its  tri- 
cuspid,  have  never  failed  it.  To  the  eye  of  the  intellect  there  is  nothing 
lost  in  transferring  it  from  the  regions  of  metaphor  and  speculation  to 
the  domain  of  physical  science. 

The  doctrine  of  the  circulation  of  the  blood  was  first  propounded  by 
Harvey's  doc-  Dr.  HARVEY  about  two  hundred  years  ago.  It  originated 
cuiTtionof  the  *n  t^ie  discovering  of  the  valves  of  the  veins  by  Fabricius  ab 
blood.  Aquapendente.  After  many  years  of  discussion,  it  was  re- 

luctantly received  by  the  medical  profession. 

In  this  doctrine  the  circulation  is  referred  to  causes  that  are  purely 
mechanical,  in  the  strictest  acceptation  of  that  term.  The  contraction 
of  the  walls  of  the  heart  propels  the  blood  through  the  arterial  tubes, 
and  even  through  the  veins,  the  direction  of  its  movement  being  insured 
by  a  proper  arrangement  of  valves. 

But  when  comparative  anatomy  and  physiological  botany  were  more 
Its  imperfec-  extensively  cultivated,  it  was  seen  that  this  doctrine  is  insuf- 
tions.  ficient,  for  the  unity  of  nature  forbids  us  to  believe  that  nu- 

tritious juices  are  circulated  in  different  tribes  of  life  by  different  forces. 
And  though  it  may  be  that  the  contractions  of  that  central  impelling 
mechanism  regulate  the  circulation  in  those  organisms  which  have  a  heart, 
what  is  to  be  made  of  those  countless  numbers  which  have  none  ?  In 
this  group  we  find  the  whole  vegetable  creation,  and  a  majority  of  the 
animal. 

There  is  a  physical  principle  which  has  long  appeared  to  me  sufficient. 
Physical  prin-  Its  use  in  an  explanation  of  the  motion  of  nutritive  juices  in 
iSecaptilary  organized  systems  of  every  class  I  have  taught  in  the  Uni- 
circulation.  "  versity  for  many  years.  It  possesses  the  advantage  of  gen- 
erality, since  it  is  applicable  in  every  case,  from  the  circulation  taking 
place  in  a  closed  cell  up  to  that  of  man. 


PHYSICAL  PKINCIPLE   OF  THE   CIPtCULATION.  131 

In  Chapter  VI.  is  a  general  statement  of  the  phenomena  and  laws  of 
capillary  attraction ;  the  principle  now  to  be  employed  is  closely  connect- 
ed therewith.  It  may  be  stated  as  follows : 

If  two  liquids  communicate  with  one  another  in  a  capillary  tube,  for 
the  substance  -of  which  they  have  affinities  of  different  intensities,  move- 
ment will  ensue :  the  liquid  having  the  highest  affinity  will  occupy  the 
tube,  and  may  even  drive  the  other  before  it.  The  same  eifect  will  en- 
sue in  a  porous  structure. 

Fig.  51.  Thus,  let  &,  #,  Fig.  51,  be  a  capillary  tube 

of  any  kind,  which  is  occupied  conjointly  by 

Motion  in  a  capillary  tube.  two  liquids,  a  and  v,  meeting  each  other  in 
its  middle,  c;  a  having  a  high  and  v  but  little  affinity  for  the  substance 
of  which  the  tube  consists,  a  will  occupy  the  tube,  pressing  out  v  before 
it.  Of  course,  it  is  to  be  understood  that  the  liquids  a  and  v  respect- 
ively communicate  with  reservoirs  that  can  furnish  them  a  necessary 
supply. 

The  various  phenomena  described  under  the  designation  of  endosmo- 
sis*  are  experimental  illustrations  of  the  same  kind.  Thus,  A  Hed  to  thc 
when  water  is  put  on  one  side  of  a  piece  of  bladder,  and  al-  explanation  of 
cohol  on  the  other,  the  water,  having  the  highest  affinity  for  ei 
the  substance  of  which  the  bladder  consists,  occupies  the  pores  thereof, 
and  expels  the  alcohol.  Nor  would  any  of  the  latter  substance  find  its 
way  in  the  opposite  direction,  back  into  the  water,  were  it  not  so  soluble 
or  diffusible  in  that  liquid.  Exosmosis  therefore  takes  place  through 
the  water,  and  constitutes  a  very  subordinate  or  feeble  current. 

Now  it  is  precisely  relations  of  this  kind  that  are  observed  in  the  case 
of  the  circulating  and  nutritive  juices  of  all  organic  beings. 

The  simplest  instance  is  presented  by  the  fluid  contents  of  certain  nu- 
cleated cells,  both  among  animals  and  plants,  in  which  a  cur-  Circulation  iu 
rent  moves  toward,  and  then  from,  the  nucleus,  coming  back  nucleated 
in  a  returning  path.  The  fluid  which  the  cell  contains  yields  c 
to  the  nucleus,  in  which  seems  to  be  concentrated  all  the  activity  of  the 
organism,  the  nutritive  material  it  requires,  and,  this  done,  passes  on  to 
make  way  for  other  portions.  The  act  of  nutrition,  therefore,  is  followed 
by  motion,  and  this  upon  the  above  simple  principle ;  for  the  liquid,  be- 
fore it  approaches  to  the  nucleus,  is  charged  with  material  which  the  nu- 
cleus can  attract ;  but  immediately  after  contact  has  taken  place,  and  the 
material  has  been  removed,  the  liquid  maintains  no  longer  any  relation  with 
the  nucleus,  the  affinity  or  attraction  is  satisfied,  and,  so  to  speak,  it  loses 
its  hold  thereupon,  and  is  pressed  off  by  new-coming  portions.  Before  its 
approach,  and  after  its  departure,  the  liquid  has  opposite  relations  to  the 
nucleus,  and  in  this  respect  may  be  regarded  as  representing  two  liquids, 
the  one  having  a  high  affinity,  and  the  other  none,  for  the  nucleus.  The 


132 


CIRCULATION   IN   CELLS. 


Circulation  in  vegetable  cells. 


Circulation  in  Tradescantia. 


Fi9- 52-  circulation  in  vegetable  cells  is  shown  by  the  di- 

rection of  the  arrows  in  Fig.  52.  The  course  taken 
by  the  current  may  be  determined  under  the  mi- 
croscope by  the  minute  floating,  or,  rather,  drifting 
granules.  It  is  to  and  then  from  the  nucleus. 

fig.  53  represents  one  of  Fig.  53. 

the  jointed  hairs  from  the 
Tradescantia  Yirginica.  The 
engraving  is  from  the  view 
given  by  Mr.  Slack,  correct- 
ed, however,  by  the  aid  of  a 
photograph  of  a  similar  ob- 
ject, a,  ^  c,  d  are  the  suc- 
cessive cells  of  the  hair.  The 
dotted  lines  show  the  direction  of  the  current  to 
and  from  the  nucleus. 

The  juice  which  is  about  to  nourish  a  part  has 
Circulation  ^or  *^at  Part  a  certam  affinity,  but,  with  the  accomplishment 
through  per-  of  that  nutrition,  the  affinity  is  at  once  lost.  Thus,  for  in- 
us  parts.  gtance?  in  the  systemic  circulation,  the  parts  to  be  nourished 
have  a  certain  affinity  for  the  arterial  blood ;  they  take  from  it  whatever 
their  purposes  require,  and,  that  done,0the  relation  at  once  ceases ;  the 
blood,  become  venous,  has  lost  its  hold  upon  them,  and  is  pressed  off. 
We  may  conveniently  describe  this  effect  as  a  pressure  of  the  unchanged 
upon  the  changed  liquid. 

The  motions  of  the  sap  in  plants  are  clearly  dependent  on  this  prin- 
Expianation  of  ciple.  Leaving  out  of  consideration  the  minor  movements 
scenTof tbfslp  w^cn  ta^e  place  for  special  purposes,  or  at  specific  epochs 
of  plants.  in  the  development,  it  may  be  truly  said  that  the  nutritive 
changes  occurring  in  the  leaf  are  the  primary  cause  of  the  motion ;  for,  as 
the  ascending  sap  presents  itself  on  the  sky  face  of  the  leaf,  it  receives 
carbon,  under  the  influence  of  the  sunlight,  from  the  air,  and  becomes  con- 
verted into  a  gummy,  glutinous  liquid.  And  just  as  in  the  pores  of  a 
bladder,  or  in  those  of  any  pervious  mineral,  pure  water  will  drive  out 
gum-water,  and  occupy  the  pore,  so  will  the  ascending  sap  expel  the 
gummy  solution  from  the  capillary  tubes  or  intercellular  spaces  of  the 
leaf.  As  fast  as  this  takes  place,  the  active  liquid  becomes  inactive,  by 
itself  changing  into  a  gummy  solution,  and  the  movement  is  perpetuated. 
And  this  ensues  not  only  in  the  leaf,  but  in  every  part  of  the  plant ;  the 
liquid  to  be  changed  presses  upon  that  which  has  changed,  and  forces 
it  onward.  In  this  manner,  motions  in  various  parts  and  of  very  great 
intricacy  will  ensue,  but  all  of  them,  if  duly  considered,  no  matter 
whether  their  seat  be  in  the  root  or  in  the  bark,  in  the  flowers  or  in  the 


CAUSE  OF  THE   CAPILLARY  CIRCULATION.  133 

leaves,  no  matter  whether  they  take  place  in  the  height  of  summer  or 
just  at  the  close  of  winter,  when  the  sap  first  rises,  or  even  in  the  germ- 
inating seed  which  is  under  the  ground,  and  has  never  yet  been  exposed 
to  the  light,  may,  without  difficulty,  be  referred  to  the  nutritive  change 
earned  on  in  the  leaves  of  the  plant  under  examination,  or  its  parent,  by 
the  influence  of  the  rays  of  the  sun. 

All  this  holds  good,  not  only  in  the  nutrition  of  a  cell,  the  more  com- 
plicated nutrition  of  the  various  parts  of  a  flowering  plant,  or  Explanation  of 
even  of  an  animal,  but  likewise  in  those  destructive  changes  circuSionof 
restricted  to  the  latter  class,  and  arising  in  interstitial  decay ;  animals, 
for  the  blood  has  a  double  duty  to  perform :  it  not  only  serves  for  nutri- 
tion, but  also  for  the  removal  of  effete  and  dying  parts.  These  it  effects 
the  oxidation  of,  their  carbon  passing  into  carbonic  acid,  their  hydrogen 
into  water ;  and  this  is  accomplished  by  the  oxygen  which  has  been  ob- 
tained in  the  process  of  respiration.  The  scarlet  or  arterial  blood,  charged 
with  its  oxygen,  passes  to  all  parts  of  the  economy  in  search  of  organic 
particles  ready  to  be  removed;  it  effects  their  disorganization,  and,  becom- 
ing thereby  venous,  is  pressed  onward.  And  now,  if  we  recall  that  nu- 
trition in  animals  depends  on  the  access  of  air— even  fibrin  can  not  arise 
from  albumen  except  under  that  condition— we  can  not  avoid  the  con- 
clusion that  all  operations  of  repair  and  all  operations  of  waste  are  made 
to  conspire  together  for  the  production  of  movement ;  and  though  every 
part  offers  its  own  special  cause,  as  depending  on  nutrition,  or  disente- 
gration,  or  secretion,  they  may  be  all  grouped  together  as  the  necessary 
results  of  one  more  primitive  operation,  which  is  the  supply  of  oxygen 
to  the  blood  in  the  respiratory  mechanism. 

In  my  view  of  this  subject,  it  is  therefore  the  arterialization  of  the 
blood  in  the  lungs  which  is  the  cause  of  the  circulation  in  De  en(ience  of 
man.  I  consider  the  circulation  as  the  consequence  of  res-  circulation  in 
piration ;  and  though,  in  one  sense,  the  minor  causes  are  the  resPiratlon- 
numerous,  each  portion  of  nervous  material,  each  muscular  fibre,  every 
secreting  cell  working  its  own  way,  these  subordinate  actions  are  all 
referable  to  one  primordial  act,  and  that  is  the  exposure  of  the  blood  to 
the  air. 

Whatever,  therefore,  interferes  with  respiration,  interferes  with  circula- 
tion. If  an  irrespirable  gas  is  thrown  into  the  cells  of  the  lungs,  the 
passage  of  the  blood  is  instantly  arrested,  and  asphyxia  ensues.  Or,  if 
the  access  of  the  air  is  cut  off,  as  in  drowning,  in  vain  the  heart  exerts 
its  utmost  convulsive  throb — it  is  unable  to  drive  forward  the  Case  of  res- 
blood;  and  in  those  cases,  by  no  means  infrequent,  yet  un-  deathT^"1 
doubtedly  the  most  surprising  occurring  in  the  practice  of  drowning. 
medicine — restoration  from  death  after  drowning,  the  whole  success  turns 
on  one  condition,  the  re-establishment  of  the  arterialization  of  the  blood. 


134  COURSE  OP  THE  CIRCULATING  BLOOD. 

If  that  be  accomplished,  the  circulation  is  restored,  and  the  heart  pro- 
ceeds with  its  duty.  And  for  these  reasons,  I  believe  that  in  many  cases 
success  would  be  had,  where  failures  are  now  experienced,  if,  instead  of 
resorting  to  atmospheric  air,  pure  oxygen  gas  or  protoxide  of  nitrogen 
were  administered. 

In  the  more  highly-developed  organisms  the  objects  of  the  circulation 
are  threefold :  1st.  To  minister  to  the  nutrition  of  the  system ;  2d.  To 
introduce  oxygen ;  3d.  To  remove  the  products  of  waste.  In  man,  these 
various  results  are  accomplished  by  several  different  arrangements  :  1st. 
Different  ^e  greater»  or  systemic  circulation ;  2d.  The  less,  or  pulmo- 
ciasses  of  nary  circulation ;  3d.  The  portal  circulation ;  4th.  The  Malpi- 

circulation.   g^  circulatioilj  &c. 

The  course  taken  by  the  blood  is  as  follows.  Leaving  the  left  ventri- 
Courseofthe  c^e  of  the  heart,  it  passes  into  the  aorta,  and  is  distributed 
blood  in  its  sys-  by  the  ramifications  thereof,  constituting  the  systemic  arte- 

temic  and  pul-     .  -,-,  f  .-,  T,  1,11 

monaiy  circu-  nes>  to  all  parts  of  the  system.  It  moves  onward  through 
lations.  the  capillaries,  which  may  at  once  be  considered  as  the  term- 

inal ramifications  of  the  arteries  and  the  commencing  tubelets  of  the 
veins.  These,  converging  into  larger  and  larger  venous  trunks,  the  sys- 
temic veins,  deliver  it  into  the  ascending  and  descending  vense  cavas,  from 
which  it  flows  into  the  right  auricle,  and  from  thence  into  the  right  ven- 
tricle of  the  heart.  From  thence  it  is  driven  into  the  pulmonary  artery, 
to  be  distributed  to  the  lungs,  and,  coming  therefrom  along  the  pulmo- 
nary veins,  reaches  the  left  auricle,  and  from  thence  it  gains  the  left  ven- 
tricle, which  was  its  starting-point. 

In  the  pulmonary  veins,  the  left  cavities  of  the  heart,  and  in  the  sys- 
Dristribution  of  temic  arteries,  the  blood  is  crimson.  In  the  systemic  veins, 
crimson  and  of  the  right  cavities  of  the  heart,  and  pulmonary  artery  and  its 
branches,  it  is  blue.  The  change  from  crimson  to  blue  takes 
place  in  the  systemic  capillaries,  and  from  blue  to  crimson  in  the  pulmo- 
nary. The  systemic,  or  greater  circulation,  is  considered  as  beginning 
at  the  left  ventricle  and  ending  at  the  right  auricle ;  the  pulmonary,  or 
less  circulation,  begins  at  the  right  ventricle  and  ends  at  the  left  auri- 
cle. This  double  course  is  sometimes,  among  authors,  illustrated  by 
likening  it  to  the  figure  8,  the  upper  loop  representing  the  pulmonary, 
the  lower  the  systemic  circulation,  and  the  heart  placed  at  the  nodal  point. 

As  has  just  been  remarked,  there  are  other  subordinate  circulations, 
The  portal  but  of  these  only  one  need  attract  our  attention  at  present — it 
circulation.  js  tne  portal.  This  originates  in  a  system  of  capillaries,  the 
veins  belonging  to  the  digestive  apparatus,  which,  converging  rapidly  to- 
gether, form  a  common  trunk,  the  portal  vein.  This  at  once  ramifies 
like  an  artery  in  the  substance  of  the  liver.  From  the  resulting  capilla- 
ries, the  portal  blood  passes  into  the  commencing  capillaries  of  the  hepat* 


ORIGIN   OF   THE   HEART. 


135 


ic  veins,  which  empty  into  the  inferior  vena  cava,  and  so  it  reaches 
the  general  circulation.  The  physical  peculiarity  of  the  portal  cir- 
culation is,  that  it  commences  in  a  capillary  system,  and  ends  in  one, 
without  the  intervention  of  any  central  organ  of  impulse,  or  heart.  At  a 
very  early  period,  comparative  anatomists  were  struck  with  Portal  circuia- 
the  analogy  between  the  portal  circulation  in  man  and  the  J^^j^t^fa*1 
systemic  circulation  of  fishes,  both  being  carried  on  in  the  fish, 
same  way,  that  is,  without  a  heart.  In  fishes,  the  heart  is  a  branchial, 
respiratory,  or  pulmonary  one.  Their  systemic  circulation,  or  circula- 
tion of  crimson  blood,  commences  in  the  capillaries  of  the  respiratory  ap- 
paratus, the  gills ;  a  convergence  takes  place  into  an  aorta,  which  ramifies 
into  systemic  capillaries.  So  the  great  circulation  in  these  tubes  is  ac- 
complished without  any  heart.  It  is  scarcely  necessary  to  point  out  the 
bearing  of  such  a  fact  on  the  theories  of  the  movement  of  the  blood. 

In  Fig.  54  is  a  diagram  of  the  circulation  of  a  fish ;  a, 
is  the  auricle ;  £,  the  ventricle ;  c,  the  branchial  or  pulmo- 
nary artery;  £,  e,  the  branchial  or  pulmonary  veins,  bring- 
ing blood  from  d,  the  branchiae,  and  converging  directly  to 
/",  the  aorta,  which  distributes  the  systemic  blood.  This 
is  collected  into  a  vena  cava,  <?,  and  so  brought  to  the  au- 
ricle, a.  There  is  therefore  no  systemic  heart. 

The  further  discussion  of  this  subject  will  be  continued 
as  follows :  We  shall  describe,  1st,  the  construction  and 
action  of  the  heart ;  2d,  of  the  arteries ;  3d,  of  the  capil- 
laries ;  4th,  of  the  veins.  We  shall  then  present  a  view 
of  the  combined  result  of  these  various  mechanisms. 

1st,  The  Heart.  The  first  appearance  of  the  heart  is  as 
a  cavity  arising  in  a  collection  of  cells,  by  cleli- 

J  „,  AX    The  heart. 

quescence  or  separation  of  the  central  ones.     At 
this  early  period,  and  even  before  the  cavity  has  fairly  formed,  pulsation 
may  be  observed.     The  organ  soon  assumes  a  tubular  form ;  and  this, 

becoming  curved,  as  shown  in  Fig. 
55,  differentiates  into  three  compart- 
ments, with  arterial  and  venous  con- 
nections ;  1,  the  venous  trunks ;  2, 
the  auricle ;  3,  the  ventricle ;  4,  the 
bulbus  arteriosus.  The  form  to  be 
eventually  assumed  is  foreshadowed  in  the  manner  in  which  the  curved 
tube  develops,  the  arch  of  the  curve,  2,  bulging  so  as  to  form  a  conical 
ventricle.  This  tri-chambered  heart  remains  permanent  in  fishes,  as  seen 
in  the  preceding  figure  (54),  of  which  c  is  the  third  chamber.  But  in  birds 
and  mammals,  the  aortic  bulb  merges  into  the  ventricle,  through  which, 
as  well  as  through  the  auricle,  a  septum  or  partition  is  established,  and 


Diagram  of  fisli 
circulation. 


Fig.  55. 


Rudimentary  heart 


136 


STRUCTURE   OF   THE   HEART. 


Diagram  of  single  heart. 


Fig.  56.  thus  a  double  heart,  or  one  of  four  cham- 

bers, arises. 

The  diagram,  Fig.  56,  represents  a 
double-chambered  heart,  d  being  its  auri- 
cle, e  the  ventricle,  c,  <?,  the  veins  converg- 
ing to  the  auricle,  a  the  aorta  or  main  arte- 
ry passing  from  the  ventricle.  The  course 
of  the  blood  is  indicated  by  the  arrows. 

The  heart  with  four  cavities  may  be 
considered  as  arising  from  the  conjunction 
of  a  pair  of  the  preceding  form,  with  their 
efferent  and  afferent  tubes,  or  arteries 
and  veins,  so  modified  or  arranged  that 
the  right  heart  receives  its  blood  from  the 
system  in  an  auricle,  from  which  it  passes  into  a  ventricle,  and  thence  to 

the  lungs.  From  the  lungs,  after  aeration, 
this  blood  is  brought  to  the  auricle  of  the 
left  heart,  thence  into  its  ventricle,  and 
thence  to  the  aorta.  Though  all  four  cham- 
bers are  generally  coalesced  into  one  conic- 
al form,  the  heart  of  the  dugong,  Fig.  57, 
presents  the  true  typical  structure;  E  is 
the  right  or  pulmonary  ventricle,  L  the  left 
or  systemic  ventricle,  their  apices  being 
quite  apart ;  D  is  the  right  or  systemic  au- 
ricle, F  the  pulmonary  artery,  K  the  left  or 
Heart  of  the  dugong.  pulmonary  auricle,  and  A  the  aorta. 

Fig.  58  is  the  anatomy  of  the  human  heart  as  viewed  upon  the  right 

side,  the  figure  and  description  being 
from  Dr.  E.  Wilson.  1,  the  cavity  of 
the  right  auricle ;  2,  the  appendix  au- 
ricuke ;  3,  the  superior  vena  cava, 
opening  into  the  upper  part  of  the 
right  auricle;  4,  inferior  vena  cava; 
5,  the  fossa  ovalis ;  the  prominent 
ridge  surrounding  it  is  the  annulus 
ovalis;  6,  the  Eustachian  valve;  7,  the 
o  opening  of  the  coronary  vein ;  8,  the 
coronary  valve ;  9,  the  entrance  of  the 
auriculo- ventricular  opening;  a,  the 
right  ventricle ;  &,  c,  the  cavity  of  the 

Human  heart  on  the  right  side.  right  Ventricle,   On  the  walls    of  which 

the  columnce  earner  are  seen ;  c  is  placed  in  the  channel  leading  upward 


STRUCTURE   OF   THE   HEART. 


137 


to  the  pulmonary  artery,  d;  e,f,  the  tricuspid  valve :  e  is  placed  on  the 
anterior  curtain,  and/*  on  the  right  curtain ;  #,  the  long  columna  carnea, 
to  the  apex  of  which  the  anterior  and  right  curtains  of  the  tricuspid 
valve  are  connected  by  the  chordaa  tendineas;  h,  the  long  moderator 
band ;  i,  the  two  columnse  carneaa  of  the  right  curtain ;  &,  the  attach- 
ment by  chorda3  tendinea3  of  the  left  limb  of  the  anterior  curtain ;  I,  I, 
chorda3  tendinese  of  the  fixed  curtain  of  the  valve ;  m,  the  valve  of  the 
pulmonary  artery :  the  letter  of  reference  is  placed  on  the  inferior  semi- 
lunar  segment ;  n,  the  apex  of  the  right  appendix  auriculas ;  o,  the  left 
ventricle ;  JP,  the  ascending  aorta ;  #,  its  arch,  with  the  three  arterial 
trunks  which  arise  from  the  arch ;  r,  the  descending  aorta. 

Fig.  59  exhibits  the  view  of  the  organ  on  its  left  side.     Like  the  pre- 
Fig  59  ceding,  the  figure  and  description 

are  from  Dr.  Wilson.  1,  cavity 
of  the  left  auricle :  the  number 
is  placed  on  that  portion  of  the 
septum  auricularum  correspond- 
ing  Tftifa  the  centre  of  the  fossa 
ovalis  ;  2,  cavity  of  the  appendix 
auriculas ;  3,  opening  of  the  two 
right  pulmonary  veins ;  4,  the 
sinus  into  which  the  left  pulmo- 
nary veins  open ;  5,  the  left  pul- 
monary veins ;  6,  the  auriculo- 
ventricular  opening;  7,  the  coro- 
nary vein,  lying  in  the  auriculo-ventricular  groove ;  8,  the  left  ventricle ; 
9,  9,  the  cavity  of  the  left  ventricle.  The  numbers  rest  on  the  septum 
ventriculorum.  a,  the  mitral  valve :  its  flaps  are  connected  by  chordaa 
tendineas  to  £,  £,  b,  the  columnaa  carneaa ;  c,  c,  fixed  columnas  carneae,  form- 
ing part  of  the  internal  surface  of  the  ventricle ;  d,  the  arch  of  the  aorta, 
from  the  summit  of  which  the  three  arterial  trunks  of  the  head  and  up- 
per extremities  are  seen  arising ;  -0,  the  pulmonary  artery ;  f,  the  oblit- 
erated ductus  arteriosus  ;  g,  the  left  pulmonary  artery ;  A,  the  right  ven- 
tricle ;  i,  the  point  of  the  appendix  of  the  right  auricle. 

Externally,  the  heart  is  covered  by  a  serous  membrane,  pericardium, 

and  in  its  interior  is  sheathed  by  the 
endocardium,  an  extension  of  the  inte- 
rior coat  of  the  great  blood-vessels. 
Though  its  movements  are  wholly  in- 
voluntary, its  muscular  fibres  are  of  the 
transversely  striated  kind.  They  are 
about  one  third  less  in  diameter  than 
Muscular  fibres  of  the  heart.  those  of  voluntary  muscles  generally, 


Human  heart  on  the  left  side. 


138  COUESE   OF   THE   BLOOD  IN  THE  HEART. 

and  are  especially  characterized  by  their  disposition  to  anastomose  with 
one  another,  as  represented  in  Fig.  60.  In  the  ventricles,  the  arrange- 
ment is  such  that  the  fibres  of  the  external  and  internal  surfaces  decus- 
sate. 

The  motions  of  the  heart  consist  in  the  relaxations  and  contractions  of 
Eelaxations  the  muscular  walls  of  its  cavities.  The  two  auricles  contract 
dons^fThe"  at  tf16  same  moment,  as  do  also  the  two  ventricles,  but  the 
heart.  contractions  of  the  auricles  coincide  with  the  relaxations  of  the 

ventricles. 

The  course  of  the  blood  through  the  heart  is  this.  The  venous  blood, 
Course  of  the  brought  by  the  ascending  and  descending  cava3,  flows  into 
blood  in  the  the  right  auricle  as  it  is  dilating,  and  for  the  moment  pushes 
movements  of  forward  to  the  ventricle,  but  the  auricle,  being  of  less  capac- 
the  valves.  fry  than  ^Q  ventricle,  is  rilled  to  distention  first ;  at  this  in- 
stant it  contracts,  forcing  its  contents  past  the  tricuspid  valve  into  the 
ventricle,  and  fills  it  completely.  The  blood  can  not  regurgitate  into  the 
veins  to  any  extent  while  this  is  going  on,  because  of  the  almost  perfect 
closure  of  their  valves.  The  right  ventricle  now  commences  to  contract ; 
its  fleshy  columns  shorten  so  as  to  pull  upon  the  tendinous  cords  attach- 
ed to  the  flaps  of  the  tricuspid  valve :  this  enables  the  blood  to  get  be- 
hind them,  and  they  quietly  close  the  aperture  between  the  auricle  and 
ventricle ;  the  closure  is  riot,  however,  under  all  circumstances,  perfect, 
the  mechanism  being  such  as  to  permit  leakage  or  regurgitation  to  a  lim- 
ited extent.  The  blood  now  rushes  into  the  pulmonary  artery,  passing 
by  its  semilunar  valves,  which,  the  moment  the  ventricular  pressure 
ceases,  shut,  so  as  to  prevent  any  return  to  the  heart. 

Having  passed  through  the  lungs  and  been  submitted  to  the  air,  the 
blood  now  returns  to  the  left  auricle,  which  forces  it  into  the  left  ventri- 
cle, the  action  on  this  side  of  the  heart  being  the  same  as  on  the  other; 
the  mitral  valve,  which  closes  the  opening  from  the  auricle  into  the  ven- 
tricle, is  worked  in  the  same  manner  as  the  tricuspid,  and  the  blood  is 
pressed  into  the  aorta,  the  semilunar  valves  of  which,  at  that  instant, 
shut  abruptly  with  an  audible  sound,  and  prevent  any  regurgitation.  In 
this  manner  the  distribution  to  the  system  is  accomplished. 

On  both  sides  of  the  heart,  as  soon  as  the  auricles  have  finished  their 
contraction,  they  begin  to  dilate,  and  continue  to  do  so  during  the  peri- 
od that  the  ventricles  are  contracting.  Thus  there  is  an  accumulation 
in  them  when  the  ventricles  are  ready  to  dilate,  and,  as  soon  as  that  oc- 
curs, the  blood  flows  freely  forward  into  those  cavities,  the  complete  dis- 
tention of  which  is  then  accomplished  by  the  contraction  of  the  auricles, 
as  before  explained. 

Movements  of  The  mode  of  action  of  the  two  sets  of  cavities  is  different, 
and  ventricles.  Tlie  auricles  contract  suddenly,  first  at  the  place  of  junction 


MOVEMENTS  OF  THE  HEART.  139 

of  their  veins,  the  effect  passing  quickly  forward ;  the  ventricles  con- 
tract more  slowly,  but  simultaneously  in  every  part. 

During  each  beat  of  the  heart  two  sounds  may  be  heard,  followed  by 
a  silence.  The  first  sound  is  dull ;  the  second,  which  fol-  Sounds  of  the 
lows  it  quickly,  is  sharp.  They  may  be  imitated  by  artic-  heart- 
ulating  the  syllables  lubb,  dup.  The  first  is  due  to  the  contraction 
of  the  muscular  fibres  of  the  ventricles,  and  the  striking  of  the  apex  of 
the  heart  against  the  wall  of  the  chest ;  to  a  certain  extent,  the  opening 
of  the  semilunar  valves,  and  the  rush  of  the  blood  into  the  pulmonary 
artery  and  aorta  contribute  to  it.  The  second  sound  is  due  to  the  shut- 
ting of  the  semilunar  valves  of  the  aorta  and  pulmonary  artery. 

At  each  contraction  of  the  ventricles  the  heart  strikes  against  the  walls 
of  the  chest,  usually  between  the  fifth  and  sixth  ribs,  and  an  inch  or  two 
to  the  left  of  the  sternum.  This  motion  is  partly  due  to  the  action  of 
the  spiral  muscular  fibres  of  the  ventricles,  which,  gives  a  tilt  to  the 
heart,  and  partly  to  the  globular  form  which  the  whole  organ  suddenly 
assumes. 

The  number  of  pulsations  made  by  the  heart  differs  very  much  at  dif- 
ferent periods  of  life:  at  birth  it  is  from  130  to  140  per  Number  of  pui- 
minute ;  at  the  seventh  year,  from  80  to  85 ;  during  mature  sations. 
life,  from  70  to  75 ;  and  in  old  age,  from  50  to  65.  In  females  it  is 
more  frequent  than  in  males.  It  observes  a  general  relation  with  the 
number  of  respirations,  five  pulsations  commonly  occurring  during  one 
respiration.  It  varies  with  incidental  circumstances.  During  sleep  it 
declines  in  frequency ;  after  eating,  or  during  exercise,  it  is  quickened. 
Examined  from  morning  to  evening,  it  becomes  slower  by  degrees.  Ly- 
ing down,  the  pulse  is  slower ;  in  a  sitting  posture,  more  frequent ;  and 
still  more  so  when  standing,  the  variations  depending  on  muscular  exer- 
tion. In  conditions  of  disease,  the  ratio  between  the  number  of  pulsa- 
tions and  respirations  is  variable. 

The  walls  of  the  left  ventricle  are  twice  as  thick  as  those  of  the  right, 
and  the  force  of  its  contractions  is  about  double.     The  ca-   Structure  and 
pacity  of  the  two  ventricles  is  nearly  the  same,  and  is  taken  power  of  the 
at  about  three  ounces.     The  active  force  with  which  the  au-  walls' 
ricles  dilate  is  feeble,  and  wholly  incompetent  to  exert  any  thing  like  the 
suction  power  at  one  time  supposed,  yet  that  they  are  not  distended  by 
the  mere  influx  of  the  blood  is  satisfactorily  proved  by  their  dilatation 
after  the  heart  has  been  cut  out. 

With  respect  to  the  absolute  force  which  the  left  ventricle  exerts  for 
the  propulsion  of  the  blood  into  the  systemic  arteries,  it  is  stated  to  be 
13  Ibs.  This  result  is  derived  from  the  consideration  that  the  pressure 
of  the  blood  in  the  aorta  is  about  4  Ibs.  3  oz. 

That  the  motions  of  the  heart  can  not  be  referred  to  the  presence  of  the 


140        CAUSE  OF  THE  MOTIONS  OF  THE  HEART. 


Cause  of  the  kloc)d>  or  an7  reflex  action  arising  from  the  cerebro-spinal 
motions  of  the  system,  but  must  be  attributed  to  the  organ  itself,  is  proved 
by  their  continuance  after  its  excision  from  the  body,  or  even 
after  it  has  been  cut  in  pieces.  Some  have  supposed  that  the  minute 
sympathetic  ganglia  with  which  it  is  furnished  are  the  source  of  the  mo- 
tive power  ;  others  are  disposed  to  impute  it  to  a  self-contractile  power 
of  its  muscular  fibres,  irrespective  of  any  nervous  agency.  Of  course,  it 
is  admitted  by  all  that  the  brain  and  spinal  cord  can  influence  these 
movements,  but  such  effects  are  superadded  and  not  uniform. 

Of  these  opinions,  we  shall  find  many  reasons  for  preferring  the  first 
when  we  come  to  the  description  of  the  nervous  mechanism.  It  will  be 
then  seen  that  one  of  the  prominent  functions  of  nervous  ganglia  of  a  cer- 
tain order,  and  particularly  the  ganglia  of  the  sympathetic,  is  the  storing 
up  of  impressions  they  have  received,  and  thus  becoming  reservoirs  or 
magazines  of  force.  The  power  thus  engendered  or  contained  in  them 
is  by  no  means  always  delivered  out  in  totality  at  once,  but  it  may  be 
in  small  portions,  at  intervals,  for  a  long  time  ;  and  doubtless  in  this 
way  the  minute  sympathetic  ganglia  of  the  substance  of  the  heart  retain 
a  power  of  keeping  up  the  motions  of  that  organ  for  a  certain  period  of 
time,  even  though  great  lesions  or  morbid  changes  may  have  supervened. 
Such  a  mechanism  recalls  the  manner  in  which  chronometers  are  kept 
going  during  the  short  time  that  the  action  of  the  main-spring  is  taken 
off  when  the  watch  is  wound  up. 

2d.  The  arteries  are  tubes  consisting  of  different  tunics  or  layers  va- 
Description  of  rioTisly  numbered  by  anatomists,  but  which  may  be  suffi- 
the  arteries.  ciently  described  as,  1st.  The  exterior  tunic,  containing  fibres 
generally  running  lengthwise,  connective  and  elastic  tissue  :  it  is  of  about 
the  same  thickness  as  the  tunic  below  ;  2d.  The  middle  tunic,  character- 
ized by  being  composed  of  non-striated  muscular  fibres  circularly  ar- 
ranged ;  3d.  The  interior  tunic,  which  is  thin,  and  consists  of  a  cellular 
or  epithelial  layer,  smooth  and  polished,  to  permit  of  the  ready  passage 
of  the  blood. 

The  elasticity  of  the  arteries  enables  them  to  sustain  the  sudden  action 
of  the  heart  by  distending  to  a  certain  degree  as  the  blood  is  driven  into 
them,  and  by  their  gradual  collapse  when  the  ventricles  cease  their  pres- 
sure, the  jetting  or  intermitting  flow  is  converted  eventually  into  a  con- 
tinuous stream.  The  mechanical  influence  of  the  heart  is  thus  decom- 
posed into  two  portions  :  one,  which  is  of  momentary  duration,  or,  at  all 
events,  lasting  only  so  long  as  the  ventricle  contracts  ;  and  a  second, 
which  is  occupied  in  distending  the  elastic  arterial  tube;  but  this  por- 
tion is  not  lost  to  the  circulation,  since  the  tube,  as  it  contracts,  yields 
it  back  again  to  the  blood.  The  momentary  impulse  of  the  heart  is  thus 
spread  over  a  considerable  duration  without  loss. 


ACTION  OF  THE   AKTERIES.  141. 

The  muscularity  of  the  arteries  is  shown  by  their  contraction  on  ex- 
posure, their  subsequent  dilatation  being  due  to  their  elasticity,  this  con- 
tractile property  being  continued  for  some  time  after  death.  It  is  also 
proved  by  the  great  diminution  of  diameter  which  arteries  exhibit  when 
under  the  influence  of  an  electric  current.  The  quantity  of  muscular 
and  elastic  tissue  in  different  arterial  tubes  is  usually  in  an  inverse  pro- 
portion. In  the  great  arteries  the  elastic  tissue  abounds,  in  the  smaller 
the  muscular  increases.  By  their  muscular  coat  the  quantity  of  blood 
in  these  tubes  can,  within  certain  limits,  be  regulated. 

At  each  injection  of  blood  into  it  an  artery  distends.  It  then  con- 
tracts, and  thus  gives  origin  to  a  pulsation.  Its  increase  is  Action  of  the 
both  in  diameter  and  length,  the  tendency  being  to  lift  it  at  arteries. 
each  pulsation.  The  distention  does  not  occur  at  the  same  instant  in 
all  these  tubes,  but  those  nearest  to  the  heart  yield  first,  and  the  more 
distant  a  little  later.  There  is  therefore  what  may  be  termed  a  wave  of 
distention  passing  throughout  the  length  of  each  arterial  tube,  and  an- 
other actual  wave  in  the  blood  itself.  These  pass  onward  at  different 
rates  of  speed.  The  interval  of  wave-motion  from  the  heart  to  the 
wrist  is  about  one  seventh  of  a  second.  Of  course  this  wave-motion  is 
to  be  distinguished  from  the  absolute  movement  of  the  blood,  which  is 
much  slower.  In  the  carotid  artery  the  flow  of  the  blood  is  about  one 
foot  in  one  second. 

A  pressure  or  impact,  communicated  to  a  liquid  in  a  long  tube,  is 
transmitted  to  the  more  distant  end  with  vastly  more  rapidity  than  the 
liquid  itself  could  flow  through  the  same  distance.  Thus,  if  we  were  to 
suppose  a  very  long  metal  tube  to  be  filled  completely  with  water,  its 
two  ends  having  been  tightly  closed  by  tying  pieces  of  bladder  over 
them,  the  tap  of  a  finger  on  one  of  the  pieces  of  bladder  would  be  almost 
instantly  felt  by  a  finger  laid  on  the  other.  Indeed,  it  has  been  pro- 
posed to  establish  telegraphic  communication  on  this  principle,  though 
such  attempts  would  prove  abortive  from  the  interference  of  collateral 
circumstances.  This  example  may  serve,  however,  to  illustrate  the  es- 
sential difference  between  the  flow  of  a  liquid  in  a  tube  and  the  passage 
of  a  pulsation  through  such  a  liquid  contained  in  such  a  tube. 

The  capillaries  may  be  regarded  as  tubular  continuations  of  the  arte- 
ries and  the  commencement  of  the  veins.  They  ramify 

,     .  J       ..      J    The  capillaries. 

through  the  organic  structures.     They  are  of  pretty  uniform 
diameter,  and  may  therefore  be  looked  upon  as  cylinders.     Their  usual 
size  is  about  -g-^-Q  of  an  inch ;  their  mode  of  distribution  varies  with  the 
structure  and  functions  of  the  part  they  occur  in :  thus,  in  muscles  they 
run  parallel ;  in  the  papillas  they  are  looped. 

They  consist  essentially  of  a  delicate  structureless  membrane,  analo- 
gous to  cell  membrane,  and  the  sarcolemma  of  voluntary  muscles.  It 


142 


THE    CAPILLAEIES. 


possesses  a  certain  degree  of  elasticity,  and  presents  here  and  there  cell 
nuclei. 

Fig.  61.  Fig.  62. 


Capillary  distribution  to  mucous  membrane  of 
stomach. 


Capillary  distribution  to  villi  of  duodenum. 


Fig.  63. 


The  interspaces  between  adjacent  capillaries  vary  much  in  size  and 
Size  of  inter-  shape,  the  latter  variation  being  dependent  on  the  mode  of 
spaces.  distribution,  whether  parallel,  reticulated,  looped,  &c. ;  as  to 

size,  in  the  liver  the  interspaces  are  of  less  diameter  than  the  capillaries, 
in  the  choroid  coat  still  smaller,  but  in  the  cellular  coat  of  the  arteries 
they  are  ten  times  larger  than  the  vessels.  These  interstitial  spaces  are 
nourished  by  the  matter  which  exudes  through  the  thin  walls  of  the  cap- 
illaries. 

Fig.  63  represents 
the  capillary  circula- 
tion in  the  web  of  the 
frog's  foot :  a,  venous 
trunk ;  £,  #,  branches 
of  venous  trunk ;  c,  c, 
pigment  cells.  The 
elliptical  blood- discs 
are  seen  in  outline  in  • 
the  interior  of  the  ves- 
sels. 

The  blood  flows 
through  the  capilla- 
ries in  an  uninterrupt- 
ed stream,  its  jetting 
motion  being  entirely 
lost.  The  rate  of  cir- 
culation through  the 

Capillary  circulation  of  frog's  foot.  SVStemic  Capillaries  is 


STRUCTURE   OF  THE  VEINS. 


143 


taken  at  three  inches  per  minute,  that  through  the  pulmo-  Motion  of  the 
nary  being  five  times  as  quick,  the  length  of  the  capillary  tube  blood  in  the 
to  be  passed  -^  of  an  inch,  so  that  the  passage  from  the  ar-  caPlllanes- 
tery  to  the  vein  may  be  accomplished  in  less  than  one  second.     It  is  to 
be  remarked,  however,  that  all  parts  of  the  cylindrical  stream  do  not 
move  with  equal  rapidity.     Those  parts  which  are  nearest  to  the  wall  of 
the  vessel  are  spoken  of  as  the  still  layer,  from  their  tardy  movement. 
It  is  in  this  that  the  white  corpuscles  may  be  seen. 

fig.  64.  Fig.  64  shows  a  portion  of  a  small 

vessel  from  a  frog's  foot:  <z,  <z,  red  blood 
elliptic  cells,  occupying  the  axis  of  the 
vessel,  and  exterior  to  them,  moving 
more  slowly,  or  occupying  the  still  lay- 
er, the  white  spherical  cells ;  b,  b,  nucle- 
ated epithelium. 

4th.  The  veins  have  a  structure  in 
some  respects  different  from  The  veins : 
that  of  the  arteries.  Their  their  structure. 
-,  elastic  coat  is  by  no  means  so  much  de- 
veloped, and  their  muscularity  less  dis- 
tinct. With  the  exception  of  those  of 
the  lungs,  abdominal  viscera,  and  brain, 
their  interior  is  furnished  with  valves  of  single,  double,  or  triple  flaps,  in 
all  instances  opening  toward  the  heart.  The  blood  flows  equably  in 
them,  the  pulsating  action  of  the  ventricles  having  disappeared  in  the 
capillaries.  Since  they  present  an  aggregate  capacity  two  or  three  times 
that  of  the  arteries,  the  motion  of  the  circulation  in  them  is  proportion- 
ally slower.  Fig.  65  is  a  diagram  showing  the  manner  in  which  the 
valves  open  when  the  blood  flows  in  the  course  indicated  by  the  arrows. 

Fig.  66. 

Fig.  65. 


Valves  of  veins  open. 


White  corpuscles  in  the  still  layer. 


Valves  of  veins  shut. 


Fig.  66  shows  their  application  to  each  other,  or  to  the  sides  of  the  vein, 
and  the  consequent  bulging  of  that  vessel  when  the  current,  as  indicated 
by  the  arrows,  is  in  the  opposite  direction. 

Having  now  described  the  structure  and  action  of  the  heart,  the  arte- 
ries, capillaries,  and  veins  respectively,  as  far  as  is  necessary,  it  remains 
to  group  those  actions  together,  and  present  the  theory  of  the  circulation 
at  one  view. 

But,  before  entering  on  this,  it  is  proper  to  offer  an  ar-  Error  of  the  doc- 
gument  against  the  doctrine  of  those  physiologists  who  still  heart  is  the  sole 
maintain  that  the  circulation  is  wholly  dependent  on  the  heart,  cause  of  the  cir- 

.  .     T  .  culation. 

and  fhnt  that  orcran  is  entirely  competent  to  carry  it  on. 


144  ACTION   OF  THE  HEART. 

The  majority  of  the  circulations  we  examine  in  organic  forms  are  ac- 
complished without  any  heart.  Plants  have  none ;  fishes  have  no  sys- 
temic heart ;  even  in  man,  at  the  first  period  of  embryonic  existence,  there 
is  no  such  central  organ  ;  in  his  adult  condition  the  portal  circulation  has 
none.  The  current  of  blood  in  the  capillaries,  seen  under  the  microscope, 
exhibits  no  jetting  movements,  but,  on  the  contrary,  a  steadiness  of 
flow,  sometimes  for  long  in  one  channel,  then  a  cessation,  then  perhaps 
a  retrogradation,  and  then  a  new  path.  It  looks  as  though  the  blood 
was  flowing  spontaneously,  and  not  by  any  force  acting  behind.  The 
heart  of  an  animal  may  be  suddenly  cut  out,  and  yet  the  capillary  motion 
may  go  on  in  the  same  direction  as  before.  After  death  the  arterial 
tubes  are  most  commonly  found  empty :  a  result  which  is  a  mechanical 
impossibility  on  the  supposition  that  the  heart  alone  drives  the  blood, 
but  which  ensues  as  a  necessary  consequence  if  the  capillaries  draw  it. 
In  acardiac  monsters  the  blood  circulates  without  difficulty,  and,  though 
it  was  at  one  time  supposed  that  in  these  twins  the  hearted  foetus  drove 
the  blood  through  the  heartless  one,  this  is  now  demonstrated  not  to  be 
the  case.  The  circulation,  moreover,  varies  locally,  and  at  special  epochs, 
as  in  the  development  of  the  generative  organs,  the  mammary  glands,  the 
flow  to  the  erectile  tissues.  Ubi  irritatio  ibi  fluxus  is  an  old  medical 
aphorism,  and  these  local  variations  are  incompatible  with  the  action  of 
one  central  unvarying  force.  In  cases  of  spontaneous  gangrene,  it  some- 
times occurs  that  the  circulation  through  the  part  has  declined,  while  the 
capillaries  are  all  open,  as  subsequent  examination  proves.  The  applica- 
tion of  cold  to  a  part  checks  the  circulation  through  it,  and  this  not 
through  any  contraction  of  the  vessels ;  so,  likewise,  does  a  jet  of  carbon- 
ic acid  gas  directed  upon  them.  Moreover,  any  retardation  in  the  supply 
of  air  to  the  lungs  restrains  the  circulation,  and  this  not  alone  in  the 
pulmonary  vessels,  but  also  in  the  systemic  capillaries,  producing  an  in- 
creased pressure  in  the  arterial  tubes,  a  diminished  one  simultaneously 
occurring  in  the  veins ;  and  if,  in  the  various  cases  now  mentioned,  the 
propulsive  action  of  the  ventricles  can  not  be  relied  on  to  explain  the  dif- 
ficulties, neither  can  any  supposed  suction  or  exhausting  action  of  the 
auricles.  When  a  ligature  is  tied  round  a  vein,  the  action  of  the  auricle 
is  cut  off,  but  the  vein  distends  beyond  the  obstruction,  showing  that 
there  is  a  force  acting  from  the  capillaries.  Flexible  tubes,  such  as  are 
those  vessels,  would  at  once  collapse  under  the  exertion  of  a  very  moder- 
ate suction  power,  far  less  in  intensity  than  would  be  necessary  to  draw 
the  blood  in  the  veins. 

In  spasmodic  asthma,  and  in  all  pulmonary  congestions,  the  right  side 
of  the  heart  circulates,  the  blood  with  difficulty  through  the  lungs,  show- 
ing the  existence  of  a  great  obstruction  to  its  motion  through  the  pulmo- 
aary  capillaries.  An  examination  of  the  condition  of  the  various  por- 


CIRCULATION   OF  THE   BLOOD.  145 

tions  of  the  circulatory  apparatus  after  death  presents  facts  utterly  inex- 
plicable on  the  doctrine  of  the  sufficiency  of  the  heart.  I  have  alrtady 
mentioned  the  empty  state  of  the  systemic  arteries ;  to  this  may  be  add- 
ed what  is  often  witnessed — the  distended  condition  of  the  pulmonary 
artery,  into  which  the  blood  has  been  forced  by  the  expiring  beats  of  the 
right  ventricle,  but  has  been  unable  to  get  through  the  pulmonary  capil- 
laries because  of  the  cessation  of  respiration ;  but  in  other  cases,  where 
respiration  has  come  to  an  end  more  tranquilly  or  slowly,  the  left  auricle 
is  full  of  blood,  which  must  have  been  driven  into  it  by  the  pulmonary 
capillaries.  In  sudden  death,  as  by  hanging  and  drowning,  the  right 
heart  is  excessively  distended,  as  is  also  the  pulmonary  artery. 

I  might  proceed  to  add  to  these  other  facts  exhibiting  local  variations 
of  the  supply  of  blood  in  the  periodicities  of  the  system.  There  is  a  cer- 
tain amount  sent  to  the  brain  during  the  day,  and  a  less  during  the  re- 
pose of  the  night ;  in  the  muscular  system,  during  the  time  of  its  action, 
the  quantity  demanded  is  greater ;  in  its  state  of  inactivity,  less.  A  con- 
stant and  invariable  acting  machine,  such  as  is  the  heart,  could  by  no 
possibility  adjust  these  variable  supplies.  But  the  cases  here  offered  are 
more  than  enough,  and  it  remains  to  be  added  that,  though,  not  one  of 
them  can  be  explained  on  the  doctrine  of  the  sufficiency  of  the  heart, 
there  is  not  one  which  does  not  follow  as  a  necessary  consequence  of  the 
doctrine  now  to  be  presented. 

On  this  view,  Ae  circulation  is  conducted  in  the  following  manner: 
The  left  ventricle  of  the  heart  impels  the  blood  into  all  the  Ex  lanationof 
aortic  branches,  any  backward  regurgitation  into  the  auricle  the  circulation 
being  prevented  by  the  shutting  of  the  mitral  valve;  the  oftheblood- 
force  employed  is  decomposed  into  two  portions,  one  part  exerting  an  in- 
stantaneous effect  on  the  blood  in  pressing  it  forward,  and  ceasing  in- 
stantaneously, and  thus  giving  origin  to  the  pulse ;  the  second  distend- 
ing the  arterial  tubes,  but  not  being  lost  thereby,  since  their  elasticity 
causes  them  to  contract,  and  the  semilunar  valves  at  the  origin  of  the 
aorta  being  at  this  period  shut,  a  steady,  onward  pressure  is  exerted  on 
the  blood ;  so  the  quickly-ending  action  of  the  ventricle  gives  origin  to 
two  distinct  mechanical  results — a  sudden  impact  and  a  continuous  press- 
ure. This  suffices  to  bring  the  blood  to  the  arterial  origin  of  the  capil- 
laries, and  beyond  that  point  the  action  of  the  heart  may  be  considered 
not  to  extend. 

The  relation  between  the  interspaces  of  the  capillaries  and  the  blood 
thus  introduced  to  them  continues  the  current.  The  particular  mode  in 
which  this  relation  is  manifested  differs  in  different  parts.  The  oxidiz- 
ing arterial  blood  has  a  high  affinity  for  those  portions  that  have  beqpme 
wasted :  it  effects  their  disintegration,  and  then  its  affinity  is  lost.  The 
various  tissues  require  repair ;  they  have  an  affinity  for  one  or  other  of 

K 


146  CIRCULATION  OF  THE  BLOOD. 

the  constituents  of  the  blood ;  they  take  the  material  they  need  and  their 
anHity  is  satisfied ;  or  secreting  cells  originate  a  drain  upon  the  blood, 
and  the  moment  they  have  removed  from  it  the  substance  to  be  secreted, 
they  have  no  longer  any  relation  with  it.  So  processes  of  oxidation,  and 
processes  of  nutrition,  and  processes  of  secretion,  all  conspire  to  draw  the 
current  onward  from  the  arteries,  and  to  push  it  out  toward  the  veins ; 
and  though  these  processes  may  present  themselves  in  many  various  as- 
pects, they  are  all  modifications  of  the  same  simple  physical  principle. 

The  blood  has  now  reached  the  veins,  and  is  forced  onward  in  them  by 
the  power  that  has  thus  originated  in  the  capillaries.  The  influence  of 
the  heart  is  here  unfelt,  the  exhausting  action  of  its  right  auricle  is  un- 
appreciable,  and,  thus  pushed  onward  from  the  capillaries,  it  reaches  the 
heart,  completing  its  systemic  or  greater  circulation.  This  circulation 
may  therefore  be  said  to  be  due  to  the  high  affinity  which  arterial  blood 
has  for  the  tissues,  venous  blood  having  none ;  and  the  action  of  the  heart 
is  confined  to  the  filling  of  the  arterial  tubes,  and  presenting  fresh  por- 
tions of  blood  to  the  capillaries. 

Arrived  at  the  right  auricle,  the  blood  flows  continuously  into  it  and 
the  right  ventricle  for  a  moment,  but  the  ventricle  holding  more  than  the 
auricle,  the  latter  cavity  is  fully  distended  first.  At  that  instant  it  con- 
tracts, the  valves  in  the  veins  shutting,  and  the  blood,  driven  thus  forcibly 
into  the  ventricle,  distends  it  to  the  utmost.  The  ventricle,  in  its  turn, 
now  contracts,  the  tricuspid  valve  shutting,  and  th*blood  issues  forth 
through  the  pulmonary  artery,  its  valves  then  closing.  At  this  moment 
an  event  occurs  which,  in  these  descriptions,  is  generally  overlooked — an 
action  analogous  to  that  of  the  hydraulic  ram.  On  the  shutting  of  the 
tricuspid,  the  whole  column  of  venous  blood  would  be  brought  to  a  stop 
if  the  tubes  containing  it  were  unyielding,  and  a  great  force  would  be  gen- 
erated from  this  stopping  of  its  momentum ;  but  the  auricle  is  ready  to 
dilate,  and  into  its  cavity  the  blood,  which  would  be  otherwise  checked, 
flows.  I  consider  that  this  safety  action  of  the  auricle  is  one  of  its  prime 
functions.  The  rapidity  with  which  the  dilatations  and  contractions  are 
taking  place  furnish  no  argument  against  the  occurrence  of  this  action. 
I  have  a  hydraulic  ram,  the  pulsations  of  which  may  be  so  adjusted  as 
to  exceed  greatly  in  frequency  those  of  the  heart,  and,  indeed,  to  give  rise 
to  a  low  murmuring  sound,  and  yet,  under  these  circumstances,  the  lat- 
eral force  is  so  great  as  to  throw  a  column  of  water  more  than  forty  feet 
high.  If  it  were  not  for  the  dilatability  of  the  auricles  and  their  yield- 
ing texture,  the  veins  would  burst  on  the  shutting  of  the  tricuspid  valve. 

The  ramifications  of  the  pulmonary  artery  bring  the  blood  to  the  cap- 
illaries of  the  lungs,  but  beyond  that  the  influence  of  the  heart  is  not  felt, 
for  now  the  physical  principle  heretofore  described  comes  again  into  ac- 
tion. The  venous  blood  has  a  high  affinity  for  the  oxygen  of  the  air,  an 


THE  HEART'S  ACTION.  147 

affinity  which  is  satisfied  as  soon  as  the  Hood  presents  itself  in  the  cells 
of  the  lungs.  Arterialization  "being  accomplished,  the  portions  to  Ibe 
changed  exert  a  pressure  on  those  that  have  changed,  and  the  blood,  mov- 
ing forward  in  the  pulmonary  veins,  reaches  the  left  auricle  of  the  heart. 

For  a  moment  it  passes  into  the  left  auricle  and  ventricle  continuously, 
but  the  auricle,  being  of  less  capacity,  fills  first.  It  contracts  as  soon 
as  it  is  completely  full,  and  drives  its  contents  into  the  left  ventricle,  dis- 
tending it  to  the  utmost.  The  ventricle  now  contracts,  shutting  the  mi- 
tral valve,  and  the  ram-like  action  is  repeated  on  this  side  of  the  heart. 
But  the  blood  expelled  from  the  ventricle  is  urged  into  the  aorta,  its  force 
being  decomposed,  as  before  described,  one  part  acting  instantaneously 
as  an  impact  on  the  blood,  the  other  on  the  arterial  walls,  and  on  the 
first  moment  of  the  recession  of  the  walls  of  the  ventricle  the  semilu- 
nar  valves  of  the  aorta  shut,  and  this  act  completes  one  tour  of  the  cir- 
culation of  the  blood. 

In  this  description  I  have  said  nothing  of  the  circulation  in  the  sub- 
stance of  the  heart  itself,  since  it  would  have  led  to  a  needless  complica- 
tion. It  should  be  remembered,  as  an  illustration  of  the  working  of  the 
physical  principle  here  explained,  that  the  motion  of  the  blood  is  contrary 
in  the  greater  and  less  circulations,  compared  together.  In  the  former, 
the  current  is  from  the  crimson  to  the  blue,  in  the  latter,  from  the  blue 
to  the  crimson  side. 

The  action  of  the  heart  is  therefore  limited  to  the  filling  of  the  arterial 
tubes,  so  as  to  present  to  the  capillaries  a  constant  supply  of  Correct  state_ 
blood.  There  seems  to  be  but  little  suction  force  exerted  ment  of  the 
by  the-  auricular  cavities  for  the  emptying  of  the  veins.  The  heart's  action< 
valvular  construction  of  these  vessels  economizes  every  pressure  that  the 
muscles  may  exert  on  them  in  favor  of  the  circulation,  for  every  such 
pressure  must,  by  reason  of  the  valves^  force  the  blood  onward  to  the 
heart.  This  is,  however,  only  an  incidental  result  of  the  same  character 
a's  the  influence  which  the  motions  of  respiration  exert.  They  may  be 
properly  overlooked  in  a  general  statement  of  the  causes  of  the  circulation. 

By  regarding  the  affinity  between  the  blood  and  the  tissues  with  which 
it  is  in  contact  as  the  great  primary  cause  of  the  circulation,  ,Various  facts 
we  assign  a  reason  for  those  various  phenomena  which  can  supporting  this 
not  be  accounted  for  on  Harvey's  doctrine :  the  motions  in  exPlanatlon- 
the  embryo ;  the  periodic  and  local  variations ;  the  portal  circulation ; 
the  changes  in  the  current,  as  seen  under  the  microscope ;  the  movement 
in  the  capillaries  after  the  heart  is  cut  out ;  the  empty  condition  of  the 
arteries  after  death ;  the  phenomena  of  acardiac  foetuses ;  local  inflam- 
mations and  congestions ;  the  gangrene  of  parts  while  their  capillaries 
are  pervious  ;  the  retardation  of  the  current  On  the  application  of  cold  or 
cf  carbonic  acid  gas  ;  the  results  of  asphyxia  and  death  by  drowning  or 


148  THE    FIEST   BREATH. 

hanging ;  the  changes  of  pressure  in  the  arteries  and  veins  respectively 
during  a  check  on  the  respiration ;  the  vis  a  tergo  of  the  veins  ;  the  effects 
of  a  ligature  on  those  vessels ;  the  action  of  irrespirable  gases  when 
breathed,  and  the  opposite  conditions  when  oxygen  gas  or  protoxide  of 
nitrogen  are  used. 

Among  the  striking  proofs  of  the  truth  of  this  doctrine,  that  the  pri- 
mary cause  of  the  circulation  is  the  aeration  of  the  Tblood,  I 
would  particularly  direct  attention  to  the  effects  which  en- 
sue in  the  moment  of  birth  at  the  first  breath.  That  intercommunication 
between  the  two  sides  of  the  heart,  established  through  the  foramen  ovale 
and  through  the  ductus  arteriosus,  is  suddenly  put  an  end  to.  But  this 
is  not  through  any  change  in  the  mechanism  of  the  heart  itself,  nor  be- 
cause of  any  interruption  in  the  action  of  the  placenta.  It  is  solely  be- 
cause of  the  calling  into  operation  of  the  principle  we  have  been  here  en- 
forcing. Through  the  contact  of  the  cold  air,  or  other  causes  which  might 
be  assigned,  the  inspiratory  muscles  make  their  first  contraction  and  dis- 
tend the  lungs.  At  that  instant,  the  commencing  arterialization  produces 
a  pressure,  in  the  manner  I  have  explained,  of  the  venous  upon  the  now 
arterialized  blood  in  the  vessels  of  the  pulmonary  cells.  There  is  no 
other  possible  issue  to  such  an  action  than  an  instant  drain  upon  the 
heart.  The  pulmonary  or  less  circulation  sets  in  with  full  vigor.  The 
blood  is  not  driven  by  the  heart  to  the  lungs,  but  drained  by  the  lungs 
from  the  heart.  If  it  were  the  heart's  action  that  occasioned  this  sudden 
increase  of  force,  because  of  the  strain  thrown  upon  it  through  the  shut- 
ting off  of  the  influence  of  the  placenta,  it  is  inconceivable  why  the  cur- 
rent should  not  continue  to  move  through  the  great  avenues  already  open 
to  it  from  the  right  to  the  left  auricle  through  the  foramen  ovale,  and 
from  the  right  ventricle  into  the  aorta  through  the  ductus  arteriosus. 
The  arrest  of  its  motion  through  these  channels  distinctly  establishes  that 
the  seat  of  the  new  action  is  in  the  lungs,  and  the  final  closure  of  the 
foramen  and  shriveling  of  the  duct  confirm  the  correctness  of  this  con- 
clusion. 

Though  it  does  not  strictly  belong  to  the  subject  now  under  consid- 
eration, I  can  not  avoid  impressing  on  the  reader  the  suddenness  of  the 
effect  that  thus  ensues  on  the  taking  of  the  first  breath.  It  is  a  crisis  in 
the  history  of  development.  Of  these  changes  by  crisis  much  more  will 
be  said  in  the  second  book,  and  their  important  bearings  on  the  theory 
of  physiology  pointed  out.  It  is  enough  for  the  present  purpose  to  com- 
mend to  the  attention  of  those  naturalists  who  deny  that  physiological 
crises  ever  occur,  the  facts  which  have  been  considered  in  the  preceding 
paragraph. 

A  doctrine  which  accounts  with  simplicity  for  such  a  long  list  of  mis- 
cellaneous facts  commends  itself  to  our  attention  at  once.  There  are, 


OP  RESPIRATION.  149 

however,  considerations  of  a  still  weightier  character,  which  must  compel 
us  to  adopt  it.  The  affinity  between  the  blood  and  the  parts  with  which 
it  is  brought  in  contact  is  a  chemical  fact  beyond  contradiction.  The 
pressures  and  motions  I  have  been  speaking  of  follow  as  the  inevitable 
consequences  of  that  affinity.  We  can  not,  therefore,  gainsay  their  ex- 
istence in  the  living  mechanism,  and  the  only  doubt  we  can  entertain  is 
as  to  whether  they  are  of  competent  power  to  produce  all  the  effects  be- 
fore us.  But  after  what  has  been  already  said  respecting  the  energy  of 
endosmotic  movements  displayed  against  pressures  of  many  atmospheres, 
we  may  abandon  those  doubts ;  and  since  we  have  here  a  force  of  uni- 
versality enough,  and  intensity  enough,  and  in  every  instance  acting  in 
the  right  direction,  it  would  be  unphilosophical  to  look  farther,  since  such 
a  force  must,  under  these  conditions,  exist  in  the  physical  necessity  of 
the  case. 


CHAPTER  IX. 

OF   RESPIRATION. 

Respiration  introduces  and  removes  aerial  Substances. —  Coalescence  of  Respiratory  and  Urinary 
Organs  in  Fishes. — Physical  and  chemical  Conditions  of  Respiration. — Interstitial  Movements 
of  Solids,  Liquids,  and  Gases. —  Condition  of  Equilibrium  in  the  Diffusion  of  Gases. — Con- 
densing Action  of  Membranes. — Forms  of  Respiratory  Mechanism. —  The  Lungs  of  Man. — 
Three  Stages  in  the  Introduction  of  Air:  Atmospheric  Pressure,  Diffusion  of  Gases,  and 
Condensation  by  Membranes. — Exchange  of  Carbonic  Add  for  Oxygen. — Divisions  of  the  Con- 
tents of  the  Lungs. —  Variations  in  the  expired  Air. — Removal  of  Water. — Effect  ofirrespira- 
ble  Gases. — Experiments  ofRegnault  and  Reiset. — Nervous  Influence  concerned  in  Respiration. 
— Results  of  Respiration. 

SINCE  it  is  essentially  necessary  to  the  life  of  all  animals  that  the 
blood  should  pass  to  every  part  of  the  system,  provision  must  objects  of 
be  made  for  securing  aeration.     The  breathing  apparatus  is  the  resPiration. 
skin,  or  some  extension,  reflection,  or  modification  of  it. 

Besides  the  great  duty  of  originating  the  circulation,  respiration  is  con- 
nected with  others  of  equal  importance.  The  functional  activity  of  the 
nervous  and  muscular  tissues  is  dependent  on  their-  oxidation,  and  this 
implies  the  introduction  of  air.  In  each  tribe,  moreover,  it  is  necessary 
to  keep  the  temperature  up  to  a  specific  point.  This  also  is  accomplished 
by  oxidation,  either  of  the  disintegrating  material  which  is  passing  to 
w^aste,  or  of  combustible  substances,  such  as  sugar  or  fat. 

All  organic  material,  at  its  death,  eventually  gives  origin,  .p. 
under  the  action  of  the  air,  to  two  products  with  which  the  of  tissue  meta- 
function  of  respiration  is  mainly  concerned.     These  products  morPhosis- 
are  carbonic  acid  and  water.     With  the  exception  of  gelatin,  the  other 


150  NATURE    OF   RESPIRATION. 

respiratory  elements  of  food — fat,  sugar,  starch,  &c.,  yield  these  two  pro- 
ducts alone.  The  nutritive  elements  give  rise  to  nitrogenized  compounds 
in  addition.  The  conditions  of  life  are  such  that  carbonic  acid  can  not 
be  permitted  to  accumulate  in  the  system,  and  means  have  therefore  to 
be  resorted  to  for  its  removal.  The  introduction  of  oxygen  and  excre- 
tion of  carbonic  acid  are  accomplished  by  the  same  mechanism,  the  lungs, 
the  action  of  which  is  'dependent  on  a  physical  principle. 

Under  its  simplest  condition,  respiration  consists  in  the  passing  of  car- 
Respiration  is  bom*c  acid  with  the  vapor  of  water  from  the  system,  and  the 
connected  tvith  reception  of  oxygen  in  exchange.  The  construction  of  the 
porous  maker  apparatus  which  accomplishes  this  double  duty  in  atmos- 
onb"-  pheric  animals  is  such  that  it  can  deal  with  substances  in 

the  aerial  state  alone.  Nothing  can  be  introduced  through  the  lungs  or 
escape  therefrom  except  it  be  in  the  gaseous  or  vaporous  form.  All 
those  products  of  disorganization  which  are  not  presented  under  this  con- 
dition must  therefore  be  removed  by  other  organs,  and  this  is  more  par- 
ticularly done  by  the  kidneys. 

But  in  aquatic  animals,  as  in  fishes  generally,  there  is  not  this  restric- 
Coaiescence  of  tion  or  concentration  of  function,  for  the  gill,  being  in  contact 
and^rhmrv^r-  w^n  water,  offers  a  channel  for  the  passing  away  of  many 
gans  in  fishes,  products  of  waste  which,  from  their  non-aerial  state,  could 
never  escape  through  a  lung,  and  so  I  regard  this  organ,  the  gill,  as  in  a 
measure  sharing  the  duty  of  a  kidney  in  eliminating  nitrogenized  and 
perhaps  saline  matters.  Comparative  anatomists  have  long  recognized 
that  the  so-called  kidney  in  fishes  approaches  in  character  the  Wolffian 
bodies  largely  developed  in  the  foetal  condition  of  man.  •  I  am  disposed 
to  believe  that  the  physical  interpretation  of  this  depends  on  the  fact  now 
before  us,  and  that  the  gill  in  fishes,  and  the  placenta,  in  part,  in  mam- 
mals, discharge  at  once  the  double  office  of  a  respiratory  and  urinary  or- 
gan. It  is  consistent  with  the  scheme  of  organic  design  that  there  should 
be  this  separation  and  concentration  of  function  as  development  takes 
place. 

These  considerations  would  therefore  lead  us  to  expect  that  we  should 
find  in  the  respiration  of  air-breathing  animals  that  function  in  its  purest 
and  least  complicated  form,  and  this  is  accordingly  the  case.  If  it  be 
merely  the  skin  that  is  relied  on,'  as  in  the  low  orders  of  aerial  life,  or  if 
the  mechanism  be  constructed  on  the  type  of  carrying  the  air  to  the 
blood,  as  in  insects,  or  that  of  carrying  the  blood  to  the  air,  as  in  man, 
the  operation  consists  essentially  in  the  escape  of  carbonic  acid  and 
steam,  and  the  reception  of  oxygen  in  return. 

Respiration,  like  circulation,  furnishes  us  with  a  signal  instance  of 
the  employment  of  purely  physical  principles  for  the  accomplishment  of 
physiological  purposes.  It  is  with  the  pressure  of  the  atmosphere,  the 


INTERSTITIAL   MOVEMENTS   OF   SOLIDS,  LIQUIDS,  GASES.  151 

diffusion  of  gases,  and  the  condensing  action  of  membranes,   _ 

rrn  •  -i  Physical  prm- 

that  we  have  now  to  deal.     These  give  us  so  precise  and  per-  cipies  alone  re- 


spicuous  an  explanation  of  the  act  of  breathing  that  it  is 

needless  to  look  beyond  them  ;  yet  on  that  act  depend  the  respiratory  en- 

highest  operations  of  life.     In  this  particular  the  Scriptures  glne 

have  summed  up  the  deductions  of  modern  physiology  in  a  single  line  — 

no  metaphorical  expression,  but  the  simple  assertion  of  a  truth  :   He 

"  breathed  into  his  nostrils  the  breath  of  life,  and  man  became  a  living 

soul." 

Of  the  physical  principles  now  to  be  dealt  with,  it  is  unnecessary  to 
say  any  thing  respecting  the  pressure  of  the  atmosphere,  since  that  is 
well  understood;  but  not  so  with  the  phenomena  of  the  diffusion  of  gas- 
es, and  the  condensing  action  of  membranes.  Though  these  are  subjects 
which  have  been  particularly  examined  by  American  physicians,  the  facts 
they  have  elicited  are  little  known  abroad.  For  example,  the  error  of 
Valentin's  statement  respecting  the  diffusion  exchanges  of  carbonic  acid 
and  oxygen,  and  the  uselessness  of  the  elaborate  discussions  which  have 
originated  therefrom,  would  at  once  have  been  recognized,  had  attention 
been  directed  to  the  facts  developed  here  almost  twenty  years  ago. 
,  Interstitial  motions  are  exhibited  by  solids,  liquids,  and  gases.  I 
have  had  occasion  to  examine  Roman  silver  coins,  from  the  interstitial 
interior  of  which  the  copper  originally  present  had  made  its  ^Ji^widK^ 
way  out  to  the  surface,  forming  the  greenish  incrustation  uids. 
known  as  patina  by  antiquarians,  the  silver  being  left  almost  pure.  In 
speaking  of  absorption  by  the  blood-vessels  in  Chapter  VI.,  we  had  oc- 
casion to  dwell  upon  the  same  propensity  as  shown  by  liquids,  the  en- 
dosmosis  of  Dutrochet  being  an  example  of  it.  The  ready  mobility  of 
this  group  of  bodies,  arising  from  their  diminished  cohesion,  greatly  pro- 
motes these  effects.  Mr.  Boyle  collected  a  number  of  cases  of  solid  move- 
ments in  his  tract  on  the  languid  motions  of  bodies. 

Gases  and  vapors,  by  reason  of  their  total  want  of  cohesion,  present  the 
most  striking  examples  of  these  effects.  Their  propensity  to  intermin- 
gle with  each  other  is  manifested,  even  though  they  be  obliged  to  pass 
through  crevices  or  winding  passages.  One  of  the  first  instances  to  which 
attention  was  directed  occurred  under  the  observation  of  Dr.  Priestley's  ob- 
Priestley,  who  found,  on  passing  steam  through  an  earthen 
tube  placed  in  a  furnace,  that  air  would  be  delivered  at  the  of  gases. 
farther  end.  For  some  time  he  supposed  that  this  experiment  demon- 
strated the  conversion  of  water  into  air  by  a  great  heatf  but  eventually 
traced  it  to  its  proper  cause  —  the  escape  of  the  steam  outward  through 
the  pores  of  the  earthen  tube,  and  the  intrusion  in  the  opposite  direc- 
tion of  air  from  the  furnace.  This  singular  experiment  may  be  well 
shown  by  attempting  to  pass  steam  through  a  red-hot  tobacco-pipe,  the 


152 


EXPEEIMENTS  OF  DALTON  AND  GRAHAM. 


Graham's  ex 


end  of  which  dips  beneath  some  water.     A  torrent  of  gas  bubbles  will 
escape. 

Mr.  Dalton  demonstrated  that  if  a  light  gas  be  placed  above  a  heavy 
Daiton'sexper-  gas  in  a  suitable  apparatus,  the  former,  notwithstanding  its 
^~nt. on  t?e  levity  will  descend,  and  the  latter,  notwithstanding  *  its 

diiiusion  01  f~ 

gases.  weight,  will  rise,  and  a  complete  and  uniform  intermixture 

will  result.  By  such  experiments  he  was  led  to  believe  that 
gases  act  as  vacua  to  one  another,  and  correctly  explained  the 
uniform  composition  of  the  atmosphere  on  this  property  of  dif- 
fusion, or  tendency  of  its  constituents  to  intermix. 

Thus,  if  a  vial  filled  with  hydrogen  be  placed  with  its 
mouth  downward  over  the  mouth  of  a  vial  of  the  same  size 
containing  carbonic  acid  gas,  as  shown  at  A,  <?,  Fig.  67,  in  the 
course  of  a  few  moments  the  diffusion  will  be  complete,  and 
if  the  mixture  in  either  vial  be  examined,  it  will  be  found  to 
contain  equal  quantities  of  the  gases. 

Professor  Graham  extended  Dr.  Priestley's  observations  on 
the  passage  through  porous  barriers.     The  sub- 
stance he  chiefly  employed  was   a  mass   of  dry 
plaster  of  Paris.     This  enabled  him  to  prove  that    Diini5ion  of 
in  the  case  of  different  gases  diffusion  takes  place  at  different 
rates,  which  are  dependent  on  the  density  of  the  gas.     Per- 
haps the  most  satisfactory  method  of  illustrating  this  class  of 
Diffusion          results  is  by  taking  a  porous  earthenware  cup, 
throughporous  a  a; Fig.  68,  such  as  is  used  in  Grove's  voltaic 
battery,  drying  it  perfectly,  and  cementing  into 
its  mouth  an  open  glass  tube,  b,  three  quarters  of  an  inch 
in  diameter,  and  a  foot  or  more  long.     A  wide-mouthed  bot- 
tle, c  c,  being  placed  as  a  temporary  cover  over  the  porous 
cup,  it  may  be  filled  with  hydrogen  gas  by  displacement ; 
and  if  the  end  of  the  glass  tube  be  put  into  water  contained 
in  a  reservoir,  d,  the  water  will  rush  up  the  moment  the 
bottle  is  removed.    When  this  motion  is  completed,  if  a  jar 
of  hydrogen  be  held  over  the  porous  cup,  the  water  will  be 
driven  down  with  great  rapidity,  and  a  number  of  air-bub- 
bles quickly  escape.     The  extraordinary  speed  with  which 
a  gas  will  flow  in  and  out  of  pores  could  not  be  better  dis- 
played.    This  rapidity  of  motion  is  an  element  with  which 
the  physiologist  has  to  deal,  as  we  shall  presently  find. 

Even  when  the  texture  of  the  substance  is  much  closer,  and  the  pores 
Diffusion      of  extreme  minuteness,  similar  results  can  be  obtained,  as  was 
through  in-  shown  in  the  experiments  of  Dr.  Mitchell,  of  Philadelphia,  who 
employed  thin  sheets  of  India-rubber.     If,  over  the  mouth  of 


Fig.  68. 


through 
earthenware. 


PASSAGE   OF   GASES   THROUGH   POROUS   FILMS. 


153 


Diffusion  through  India-rubber. 


a  glass  bottle,  such  a  thin  tissue  be  tightly  tied,  and  the  bottle  placed 
in  an  atmosphere  of  carbonic  acid  gas,  movement  at  once  takes  place,  a 
little  air  flowing  out  of  the  bottle  into  the  carbonic  acid,  and  so  large  a 
Fig.  69.  quantity  of  the  acid  passing  the  opposite  way 

that  the  India-rubber  soon  swells  outward^ 
and  eventually  caps  the  bottle  like  a  dome,  as 
in  Fig.  69,  at  b.  Or,  if  the  conditions  be  re- 
versed, the  bottle  being  filled  with  carbonic 
acid,  and  then  exposed  to  the  atmosphere,  the 
India-rubber  will  be  depressed,  as  at  #,  and 
stretch  so  as  almost  fo  sink  to  the  bottom. 
Such  experiments  therefore  prove  that,  even 
though  barriers  of  a  very  close  texture  should 
intervene,  gases  will  pass  through  them,  and 
with  so  much  force,  as  Dr.  Mitchell  showed,  that  many  inches  of  mercury 
may  be  lifted,  nor  does  the  movement  cease  until  the  gases  on  both  sides 
of  the  membrane  have  the  same  composition. 

Other  substances  having  a  close  texture  may  be  thus  'readily  permea- 
ted.    I  found  that  a  little  bladder  of  shellac,  blown  on  the  Experiments 
end  of  a  glass  tube,  permitted  the  passage  of  the  vapor  aris-  ^anTii^' 

ing  from  water  of  ammonia.  The  "ids. 
instantaneousness  of  these  motions  is,  how- 
ever, most  -beautifully  illustrated  by  employ- 
ing soap-bubbles,  the  liquid  nature  of  which 
excludes  the  idea  of  pores  in  the  strict  accepta- 
tion of  that  term.  If  a  bottle,  a  a,  Fig.  70,  be 
rinsed  out  with  amponia,  and  then,  by  means 
of  a  piece  of  glass  tube,  b  b,  a  soap-bubble,  <?, 
be  blown  therein,  the  air  from  the  bubble  be- 
ing immediately  drawn  into  the  mouth  with- 
out a  moment's  delay,  the  strong  taste  of  the 
ammonia  is  perceived.  Or  if  a  rod,  dipped  in 
hydrochloric  acid,  be  presented  to  the  projecting  end  of  the  glass  tube, 
copious  white  fumes  arise.  This  therefore  shows  that  vapors  will  pass 
through  barriers  having  no  proper  pores,  the  transit  taking  place  instan- 
taneously. 

Soap  films  enable  us  to  demonstrate  the  endosmosis  of  gases  in  a  very 
advantageous  manner,  owing  to  their  cohesiveness  and  thinness.  If  the 
finger  be  dipped  in  soap-water,  and  then  rapidly  passed  over  the  mouth 
of  an  empty  bottle,  so  as  to  leave  a  horizontal  film  attached  across,  on 
exposing  the  bottle  to  carbonic  acid  gas,  the  horizontally  of  the  film  is 
immediately  disturbed,  and  it  soon  swells  up  into  an  almost  spherical 
dome.  Or  if  the  bottle  be  filled  with  carbonic  acid,  and  then  exposed 


Instantaneous  passage  of  gases 
through  films. 


154  PASSAGE   OF   GASES   THROUGH   POROUS  FILMS. 

to  the  air,  the  film  is  promptly  depressed  into  a  deep  concavity,  and 
bursts.  By  these  methods  the  passage  of  all  kinds  of  vapors  and  gases 
may  be  demonstrated,  oxygen,  hydrogen,  carbonic  acid,  protoxide  of  ni- 
trogen, the  vapors  of  peppermint,  lavender,  and  various  essential  oils. 

By  many  experiments  on  such  different  substances,  I  found  that  the 
Law  of  e  uilib-  ^aw  °^  &|fc$*l#iaHi  f°r  gases  and  vapors  is  the  same  as  for 
rium,  and  ex-  liquids.  No  matter  what  the  thickness  or  thinness  of  a  po- 
f  lfc'  rous  barrier  may  be,  movement  takes  place  through  it,  un- 
til the  media  on  its  opposite  sides  have  the  same  chemical  composition. 
The  observed  action,  in  particular  cases,  will  therefore  altogether  depend 
on  the  circumstances  untler  which  the  experiment  is  made.  A  soap-bub- 
ble full  of  carbonic  acid,  exposed  to  the  air  in  a  closed  bottle,  collapses 
only  to  a  certain  extent,  when  the  percentage  constitution  of  the  air  it 
contains  is  the  same  as  that  of  the  air  in  the  bottle,  contaminated  with 
the  carbonic  acid  which  the  bubble  has  yielded  it.  But  if  the  bubble  be 
exposed  to  the  free  atmosphere,  it  collapses  almost  completely,  for  now 
the  carbonic  acid  escapes  finally  away. 

One  of  the  most  interesting  facts  connected  with  these  results  is  the 
Action  throu  h  Per^ect  manner  in  which  a  film  of  excessive  tenuity  will  dis- 
fiims  of  ex-  charge  these  mechanical  functions.  With  a  little  care,  a 
Ult7'  film  may  be  obtained  so  thin  as  to  be  invisible  except  in 
certain  lights,  when  it  presents  a  velvety  black  aspect.  In  this  condi- 
tion, as  Newton  has  proved,  it  is  not  thicker  than  three  eighths  of  a 
millionth  of  an  inch,  yet  endosmosis  takes  place  perfectly  through  it :  it 
expands  and  collapses,  rises  up  into  a  dome,  or  is  depressed  into  a  con- 
cavity, as  the  circumstances  of  its  exposure  may  be.  And  this  should 
prepare  us  to  admit  that  in  organic  tissues  of  the  utmost  degree  of  tenu- 
ity these  physical  phenomena  may  occur,  and  that  even  under  these  most 
unlikely  circumstances  such  tissues  may  give  origin  to  mechanical  forces 
of  the  greatest  intensity,  as  we  shall  now  prove. 

Graham's  law  of  the  diffusion  of  gases  has  but  a  very  limited  physio- 
logical  application.  The  introduction  of  it  in  cases  to  which 
of  Graham's  it  does  not  properly  apply  has  led  to  several  errors.  There 
js  nothing  common  in  the  result  of  the  movement  of  gases 
exposed  freely  to  one  another,  and  exposed  with  the  intervention  of  a 
close-pored  tissue.  The  tissue  itself  gives  origin  to  mechanical  force  of 
such  intensity  as  not  only  to  modify  the  diffusion  rate,  but,  in  a  great 
many  of  the  most  important  cases,  absolutely  to  invert  the  direction  of 
the  motion.  Thus,  through  a  stucco  plug,  in  which  the  pores  are  of 
sensible  size,  atmospheric  air  passes  more  rapidly  to  carbonic  acid  than 
carbonic  acid  does  to  it,  but  through  the  thinnest  film  of  water  just  the 
reverse  takes  place.  A  bubble  full  of  that  acid,  exposed  to  the  air,  lets 
it  escape  with  so  much  rapidity  that  in  a  few  moments  a  complete  col- 


FORCE   OF  PASSAGE   THROUGH  MEMBRANES. 


155 


lapse  lias  occurred.  If  the  law  of  diffusion  here  held  good,  the  bubble 
should  rapidly  distend. 

Moist  membranes  and  films  of  water,  by  reason  of  their  chemical  affin- 
ity for  gaseous  substances,  and  their  consequent  condensing  Condensingac. 
action,  become  the  origin  of  great  mechanical  power.  Under  tion  of  mem- 
such  conditions,  I  have  seen  carbonic  acid  pass  into  atmos- 
pheric air,  driven,  as  it  were,  by  the ;  action  of  the  membrane  against  a 
pressure  of  ten  atmospheres,  and  sulphureted  hydrogen  against  a  pres- 
sure of  twenty-five  atmospheres,  and,  even  against  these  great  resistances, 
the  passage  is  accomplished  with  so  much  promptness  as  to  lead  to  the 
inference  that  a  membrane  will  cause  one  gas  to  diffuse  into  another,  even 
though  the  apparent  resistance  be  indefinitely  great. 
mg.  7i.  In  Fig.  71  is  given  a  representation  of  the  arrangement  by 
which  these  results  were  obtained.  It  consists  of  a  strong 
glass  tube,  seven  inches  or  more  in  length  and  half  an  inch  in 
diameter,  hermetically  closed  at  one  end,  through  which  a  pair 
of  platina  wires,  £,  <?,  pass  into  the  interior  of  the  tube  parallel 
but  not  touching.  The  other  end,  a  a,  has  a  lip  or  rim  turned 
on  it.  Between  the  platina  wires,  a  gauge-tube,  d,  is  dropped, 
to  show  the  amount  of  condensation.  On  the  top  of  the  gauge- 
tube  a  small  test-tube,  f,  is  placed,  to  contain  a  reagent  suited 
to  the  gas  under  trial,  as  lime-water  for  carbonic  acid,  acetate 
of  lead  for  sulphureted  hydrogen,  litmus-water  for  sulphurous 
acid.  Sometimes,  instead  of  this  test-tube,  a  piece  of  paper, 
soaked  in  the  proper  reagent,  was  employed.  The  Measure  of  the 
large  tube  was  then  filled  with  water  to  the  height  force  of  infii- 
e  e.  Its  lip  or  rim,  a  a,  being  next  smeared  with 
burnt  India-rubber,  to  insure  absolute  freedom  from  leakage, 
a  thin  sheet  of  India-rubber  was  tied  tightly  over  it,  and  over 

Great  force  of  .  '     . J  .          — 

infiltration,  this  again,  to  give  strength,  a  very  stout  piece  of  silk.  Every 
thing  being  thus  arranged,  the  projecting  wires,  £,  c,  were  connected  with 
a  voltaic  pile,  decomposition  of  the  water  ensued,  oxygen  and  hydrogen 
being  disengaged,  and  a  condensed  mixture  of  atmospheric  air  and  those 
gases  accumulated  in  the  space  a  a  e  e,  the  gauge-tube  showing  the  ex- 
tent to  which  the  condensation  had  gone.  Now  if  the  little  tube,  f,  had 
been  filled  previously  with  lime-water,  and  the  whole  arrangement  was 
introduced  into,  a  jar  of  carbonic  acid  gas,  the  upper  part  of  the  lime- 
water  presently  became  milky,  and  after  a  time  a  copious  precipitate  of 
carbonate  of  lime  subsided.  This  would  readily  take  place  when  the 
gauge  was  indicating  a  pressure  of  ten  atmospheres.  In  like  manner, 
when  a  piece  of  paper  imbued  with  carbonate  of  lead  had  been  introduced 
into  the  tube,  and  a  pressure  of  24|  atmospheres  accumulated,  on  intro- 
ducing the  instrument  into  a  vessel  of  sulphureted  hydrogen,  the  paper 


156  GENERAL   PRINCIPLE    OF   DIFFUSION. 

quickly  became  brown.  So  sulphureted  hydrogen  can  pass  through  a 
sheet  of  India-rubber  and  diffuse  into  an  atmosphere  of  oxygen,  hydro- 
gen, and  atmospheric  air  beyond,  though  it  is  resisted  by  a  pressure  equal 
to  that  of  800  feet  of  water. 

The  method  of  condensation  here  employed,  because  of  its  freedom  from 
mechanical  concussions,  enabled  me  to  continue  these  researches  up  to 
pressures  of  50  atmospheres  without  leakage,  in  comparatively  slender 
tubes,  and  even  under  these  circumstances  gaseous  diffusion  seemed  to 
take  place  without  any  restraint. 

It  would  lead  me  too  far  from  my  present  object  to  pursue  the  con- 
General  facts  sideration  °f  these  facts,  and  I  must  therefore  be  content  to 
connected  with  refer  the  reader  to  the  memoirs  in  which  they  have  been  spe- 
diffusion.  ciajlv  discusse(k*  it  is  sufficient  to  understand,  1st.  That 
gases  simply  exposed  to  each  other  inter-diffuse  with  great  rapidity,  and 
at  a  rate  inversely  proportioned  to  the  square  root  of  their  densities  ;  2d. 
That  the  same  takes  place  through  stucco  plugs,  or  diaphragms  with  open 
pores  ;  3d.  That  a  gas  dissolved  in  a  liquid,  or  held  in  a  condensed  state 
by  a  solid  mass,  will  exchange  by  inter-diffusion  with  any  atmosphere 
to  which  it  may  be  exposed,  in  these  cases  the  liquid  or  the  solid  mass 
becoming  a  source  of  force  ;  4th.  That  through  a  liquid,  which,  of  course, 
has  no  pores,  gases  arranged  on  its  opposite  sides  will  diffuse,  but  their 
rate  is  no  longer  expressed  by  Graham's  law  ;  5th.  That  a  liquid  hold- 
ing a  gas  in  solution  permits  it  to  diffuse  with  another  gas  held  by  an- 
other liquid  in  solution. 

On  the  first  of  these  principles,  the  fresh  air  of  the  bronchial  tubes  ex- 
changes with  the  respired  air  of  the  pulmonary  cells,  the  case  being  that 
of  a  gas  exposed  to  a  gas.  On  the  third  of  these  principles,  arterializa- 
tion  of  the  blood  takes  place,  the  case  being  that  of  a  dissolved  gas  ex- 
changing with  a  free  gas  ;  and  on  the  fifth  of  these  principles,  aquatic  or 
gill  respiration  depends,  the  case  being  that  of  a  dissolved  gas  exchang- 
ing with  another  dissolved  gas. 

Under  its  simplest  aspect,  the  act  of  breathing  consists  in  the  elimina- 
Various  forms  ^on  °^  carboiu'c  acid  from  the  system,  and  the  introduction 
of  respiratory  of  oxygen.  The  manner  in  which  the  respiratory  surface 
itself  from  the  former,  and  secures  new  supplies  of  the 


mechanism. 

latter,  differs  very  greatly.  In  the  lower  orders  which  lead  an  aquatic 
life,  currents  are  established  in  the  water  by  the  aid  of  ciliary  motion,  and 
by  these  the  necessary  changes  are  made.  In  others,  in  which  respira- 
tion is  conducted  by  the  skin,  incessant  locomotion  is  relied  on  ;  and 
again,  in  others,  the  water  is  drawn  into  the  stomach  and  intestinal  canal, 
and  every  part  bathed  with  the  aerating  medium. 

In  insects,  the  type  of  carrying  air  to  the  blood  is  developed  to  the  ut- 
*  American  Journal  of  Medical  Sciences,  May,  1838. 


RESPIRATION   OF   INSECTS   AND   FISHES. 


157 


most  degree,  there  being  great  numbers  of  tracheal  tubes  pervading  all 
the  soft  parts.  These  occasionally  present  dilatations,  acting  as  reser- 
voirs— the  foreshadowing  of  the  respiratory  cavities  of  the  higher  tribes. 
Of  such,  Fig.  72,  representing  the  air-sacs  or  tracheal  dilatations  of  the 


Air-sacs  of  insects. 


Spiracle  of  insect 


scolia  liortorum,  is  an  illustration.  The  tracheal  tubes  Respiration  of 
communicate  with  the  external  air  through  openings  which  insects. 
maybe  obstructed  by  a  valvular  arrangement,  as  represented  in  Fig.  73. 
The  photograph  from  which  this  figure  was  taken  shows  such  a  spiracle 
magnified  75  diameters.  These  organs  may  be  seen  arranged  in  rows 
on  each  side  of  the  body ;  thus,  in  the  common  caterpillar,  there  are  ten 
pairs.  The  mode  of  guarding  the  orifice  varies  in  different  cases,  some- 
times tufts  of  hair  being  resorted  to,  and  sometimes,  as  in  the  figure, 
valves. 

The  true  lung  is  first  recognized  in  the  swimming  bladder  of  fishes  as 
a  simple  sac.  In  the  carp,  the  tendency  to  a  multi-chambered  construc- 
tion already  appears  under  the  form  of  two  such  bladders,  #,  #,  communi- 

eating  with  each  oth- 
er through  a  narrow 
tube.  These  are  con- 
nected with  the  oesoph- 
agus, 0,  by  means  of 
the  pipe  c  d,  the  fish 
being  thus  enabled  to 
remove  at  pleasure  a  part  of  the  air  contained  in  the  sacs  by  muscular 
compression.  Though  this  mechanism  is,  as  we  have  said,  a  rudiment- 
ary lung,  it  does  not  properly  subserve  the  duty  of  such  an  organ,  but  is 
.employed  for  producing  variations  in  the  specific  gravity  of  the  animal 
by  compression  or  rarefaction  of  the  included  air.  In  these  Respiration  of 
tribes  the  gills  are  the  mechanism  for  aeration,  which  is  ac-  fishes- 


Air-sac  of  fish. 


158 


RESPIRATION    OF   FISHES   AND    REPTILES. 


complished  in  the  following  manner :  The  mouth  is  periodically  filled 
with  water,  which  is  driven  past  the  gills  by  muscular  compression,  and 
thereby  the  carbonic  acid  is  removed  from  the  blood  which  circulates  in 
those  organs,  and  oxygen  is  obtained  in  return.  For  this  reason,  a  fish 
dies  very  quickly  when  its  mouth  is  kept  open.  The  angler  knows  that 
it  is  not  owing  to  any  loss  of  blood,  nor  to  any  injurious  lesion  that  the 
hook  may  cause,  but  simply  to  suffocation,  the  water  no  longer  lifting  the 
gill  covers,  but  merely  passing  out  through  the  open  mouth. 

The  experiments  of  Humboldt  and  Prove^al  clearly  demonstrate  the 
analogy  between  aquatic  and  aerial  respirations ;  for  water  is  not  de- 
composed by  the  breathing  of  fishes :  it  is  the  air  dissolved  in  it  that  is 
used.  In  the  sample  examined  by  these  chemists,  there  was  20.3  per 
cent,  of  its  volume  of  air,  consisting  of  oxygen  29.8,  nitrogen  66.2,  and 
carbonic  acid  4.0,  in  the  hundred  parts.  After  the  fishes  had  remained 
in  it  for  a  due  time,  it  still  contained  17.6  per  cent,  of  its  volume  of  air, 
but  this  in  100  parts  now  consisted  of  oxygen  2.3,  nitrogen  63.9,  and 
carbonic  acict  33.8.  There  had  therefore  been  a  consumption  of  oxygen 
and  evolution  of  carbonic  acid,  together  with  a  slight  removal  of  nitrogen, 
this  being  the  general  result  witnessed  in  aerial  respiration.  In  a  sim- 
ilar course  of  experiments  on  the  breathing  of  gold  fishes, 
made  by  myself,  the  result  corresponds  to  the  preceding 
statement,  only  the  water  I  used  was  richer  in  oxygen  gas, 
and  the  transposition  into  carbonic  acid  did  not  seem  by 
any  means  to  be  so  complete.  I  also  remarked  the  same 
diminution  in  the  quantity  of  nitrogen,  but  am  disposed  to 
attribute  it  not  so  much  to  the  consumption  of  that  gas  by 
the  fishes  as  to  its  diffusion  from  the  water  into  the  atmo- 
sphere, the  solvent  power  having  changed  by  the  substitu- 
tion of  carbonic  acid  for  oxygen. 

In  reptiles  the  lung  presents  the  sac-like  form,  as  in  Fig. 
Respiration  of  75,  a  pulmonary  artery  passing  on  one  side, 
reptiles.  an(j  a  pulmonary  vein  returning  on  the  other : 

a  is  the  trachea ;  #,  its  bifurcation ;  <?,  pulmonary  artery ; 
d,  d,  pulmonary  vein.  It  often  occurs  that. '"the  two  lungs 
are  not  equally  developed,  one  of  them,  B,  being  rudiment- 
ary as  compared  with  the  other,  A.  Into  such  a  sac  in  ser- 
pents the  air  is  forced  by  muscular  contraction,  a  kind  of 
swallowing.  It  is  expelled  from  them  by  the  contraction 
of  the  abdominal  muscles,  and  hence  the  hissing  sound 
which  it  emits  during  its  expulsion.  From  the  simple  sac 
to  the  cellular  lung  the  advance  is  made  by  degrees,  a  de- 
velopment of  parietal  cells  upon  the  inner  surface  taking 
place.  At  the  intermediate  stage,  between  the  simple  sac 


STRUCTURE   OF  THE   LUNGS.  159 

and  the  highly  subdivided  respiratory  organ  of  the  mammals,  the  condi- 
Fig.  T6.  tion  of  things  is  well  illustrated  by  the  lungs 

of  the  frog.  In  Fig.  76,  a  is  the  hyoid  appa- 
ratus ;  b,  cartilaginous  ring  at  the  root  of  the 
lungs  ;  c,  the  pulmonary  vessels  ;  and  d,  d,  the 
pulmonary  sacs. 

Of  all  tribes,  the  respiratory  mechanism  is 
most  highly  developed  in  birds,  Respiration  of 
which,  besides  being  provided  with  birds- 
lungs,  have  air-sacs  between  the  muscles,  and 
respiratory  membranes  spread  on  the  interior 
of  the  hollow  bones.  It  is  in  consequence  of 
this  that  a  bird  is  killed  so  readily,  even  by  a 
Lungs  of  frog.  Yerv  small  shot,  since  it  is  scarcely  possible  to 

make  a  perforation  into  any  part  of  the  body  without  opening  the  respi- 
ratory cavity. 

In  man,  the  bronchial  tube,  as  it  passes  into  each  lung,  branches  forth 
like  a  tree,  the  walls  of  the  tubelets  thus  arising  having  car- 

, .-,  .  -     .      (,  ,  .  Lungs  of  man. 

tilagmous  rings  to  preserve  their  form  under  compression, 
circular  organic  muscular  fibres  to  enable  them  to  contract,  and  longitu- 
gitudinal  fasces  of  elastic  tissue  to  shorten  them  after  extension.  In 
their  interior  they  are  covered  with  mucous  membrane  provided  with 
cilia.  When  the  proper  degree  of  minuteness,  about  -^  of  an  inch,  is 
reached,  they  consist  alone  of  elastic  membrane,  interspersed  with  mus- 
cular fibres,  and  upon  their  sides  the  air-cells  open ;  sometimes  single 
ones,  or  sometimes  many  cells  communicating  with  one  another,  discharge 
through  the  same  orifice,  the  tubelet  itself  ending  in  a  cell.  The  air- 
cells  have  various  dimensions,  from  JL  to  1 2*0  tf  of  an  inch.  Their  struc- 
ture is  like  that  of  the  tubelet.  The  pulmonary  capillaries  are  spread 
so  closely  upon  them  that  the  spaces  between  them  are  less  than  their 
own  diameters,  which,  on  an  average,  are  3-^-3-  of  an  inch.  As  the  cells 
are  close  together,  the  blood-vessels  passing  between  them  are  brought 
in  communication  with  the  air.  on  both  sides,  and  arterialization  is  thus 
rapidly  and  completely  performed.  Each  tubelet,  with  the  air-cells  thus 
clustered  upon  it,  is  a  miniature  representation  of  the  lung  of  a  reptile. 
These  cells  themselves  communicate  by  lateral  apertures  with  one  an- 
other. The  membrane  which  lines  their  interior  is  sharply  folded  at  the 
apertures,  and  there  are  reasons  for  supposing  that  it  contains  organic 
muscular  fibres.  It  is  stated  that  each  terminal  bronchus  has  nearly 
20,000  air-cells  clustered  upon  it,  and  that  the  total  number  is  600 
millions. 

The  mode  of  distribution  of  the  air-tubes  is  represented  in  Fig.  77. 
a  is  the  larynx ;  b  b,  the  trachea,  the  upper  letter  corresponding  to  the 


160 


STRUCTURE   OF   THE    LUNGS. 


cricoid  cartilage ;  c,  the  left  bronchus  ;  d,  the  right  bronchus ;  e,f,  g,  its 
ramifications  in  the  right  lung,  j  j  ;  A,  i,  ramifications  of  the  left  bron- 
chus in  the  left  lung,  k  L 

Fig.  77.  Fig.  78. 


Human  air-tubes. 


The  heart  and  lungs. 


Fig.  78,  arrangement  of  the  heart  and  lungs,  the  latter  in  part  section. 
1,  left  auricle  of  the  heart ;  2,  right  auricle ;  3,  left  ventricle ;  4,  right 
ventricle ;  5,  pulmonary  artery ;  6,  aorta ;  7,  superior  vena  cava ;  8,  in- 
nominata;  9,  left  primitive  carotid;  10,  left  subclavian, ;  11, 12,  upper 
rings  of  trachea  and  cartilages  of  the  larynx ;  13,  upper  lobe  of  right 
lung;  14,  upper  lobe  of  left  lung;  15,  right  pulmonary  artery;  16,  16, 
lower  lobes  of  lungs. 

Fig.  79  illustrates  the  manner  of 
distribution  of  blood-vessels  on  the 
air-cells  of  the  lungs. 

As  the  blood  to  be  arterialized 
passes  through  the  pulmonary  capil- 
laries, its  discs  can  only  move  in  sin- 
gle files,  and  even  then  probably  un- 
dergo a  compression  which  changes 
their  form.  As  soon,  however,  as 
they  escape  into  the  larger  vessels, 
their  elasticity  enables  them  to  recov- 

Distribution  of  capillaries  on  air-cells  of  the  lungs.    er  their  origmal  shape. 

By  the  aid  of  this  elaborately  constructed  mechanism  the  air  is  brought 
Three  stages  in  to  tne  blood.     There  are  three  distinct  stages  through  which 
the  introluc-    Jt  has  to  pass.     The  first  is  the  filling  of  the  trachea  and 
larger  ramifications  of  the  bronchial  tubes :  this  is  accom- 
plished by  atmospheric  pressure,  brought  into  play  by  muscular  contrac- 


MOVEMENTS   OF   KESPIRATION. 


161 


Fig.  SO. 


tion.  The  second  stage  is  the  translation  of  the  fresh  air  from  the  larger 
bronchial  tubes  to  the  ultimate  air-cells :  this  is  accomplished  on  the 
principle  of  gaseous  diffusion.  The  third  stage  is  the  passage  from  the 
air-cells  into  the  blood :  this  is  through  the  wall  of  the  cell,  the  wall  of 
the  blood-vessel,  and  the  sac  of  the  blood  disc ;  it  involves  passage 
through  membranes,  and  implies  their  condensing  action.  Each  of  these 
three  stages  we  have  now  to  consider. 

1st.  The  introduction  of  fresh  air  into  the  trachea  and  larger  ramifi- 
cations of  the  bronchial  tubes  is  accomplished  by  muscular  The  effect  of  the 
contraction,  which  calls  into  operation  atmospheric  pressure,  pressure  of  the 
In  tranquil  respiration  the  diaphragm  is  nearly  sufficient  for 
this  purpose.  This  muscle,  forming  the  convex  floor  of  the  chest,  as  soon 
as  it  contracts,  assumes  more  nearly  a  plane  figure,  thereby  increasing 
the  content  of  that  cavity ;  and,  just  as  in  a  common  bellows,  when  the 
lower  board  is  depressed,  the  air  flows  in  through  the  pipe,  so^on  the  de- 
scent of  the  diaphragm,  the  air  flows  in  through  the  trachea,  forced  by 
the  external  pressure. 

An  experimental  illustration  of  the  manner  in 
which  the  air  is  introduced  into  the  cavity  of  the 
lungs  by  the  descent  of  the  floor  of  the  chest, 
and  then  expelled  by  its  elevation,  is  represented 
in  Fig.  80,  in  which  a  a  is  a  tube  of  glass  half 
an  inch  or  more  in  diameter,  and  six  or  eight 
inches  long,  to  the  lower  end  of  which  a  blad- 
der, b,  is  tightly  attached.  The  tube  is  passed 
through  the  neck  of  a  bell-jar,  c  <?,  air  tight.  A 
large  glass  reservoir  of  water,  filled  to  the  height 
d  d,  receives  the  bell-jar,  as  shown  in  the  figure. 
When  the  jar  is  depressed  in  the  water  the  air 
is  expelled  from  the  bladder,  and  when  the  jar 
is  raised  the  air  flows  in.  By  alternately  ele- 
vating and  depressing  the  bell,  the  bladder  exe- 
cutes movements  like  those  of  the  lungs,  of  which, 
indeed,  it  is  a  representation;  the  glass  tube  be- 
ing the  trachea,  the  bell-jar  the  walls  of  the  chest, 
and  the  rising  and  falling  water-level  the  rising 
In  this  illustration  the  bladder  is,  of  course,  per- 


Mechanism  of  respiration. 

and  falling  diaphragm. 


fectly  passive,  as  was  at  one  time  supposed  to  be  the  case  with  the  lungs  : 
an  erroneous  opinion,  which  will  presently  be  corrected. 

In  the  mature  period  of  life,  and  especially  in  deep  respiration,  the  ac- 
tion of  the  diaphragm  is  insufficient  for  the  introduction  of  air,  Manner  of  in_ 
and  a  still  farther  volume  is  obtained  by  raising  the  ribs,  which  troducing  the 
increases  the  dimensions  of  the  chest  from  right  to  left,  and  air> 


162  MOVEMENTS   OF   EESPIEATIOX. 

also  from  front  to  back.  In  men,  this  effect* takes  place  more  particular- 
ly through  the  movements  of  the  lower  ribs,  and  this  form  of  respiration 
is  therefore  sometimes  called  the  inferior-costal ;  but  in  women  the  upper 
jibs  are  more  movable,  the  dilatation  of  the  chest  is  there  greater,  and 
the  respiration  therefore  designated  as  the  superior -costal.  In  these 
movements  of  the  ribs,  and  especially  in  violent  respiration,  many  mus- 
cles are  involved. 

In  the  reverse  act,  that  is,  in  expiration,  or  the  expulsion  of  air  through 
the  trachea,  the  floor  of  the  chest  is  raised.  The  diaphragm,  when  it 
contracted,  made  pressure  upon  the  viscera  of  the  abdomen,  and  forced 
the  muscular  walls  of  that  cavity  outward ;  but,  as  soon  as  the  diaphragm 
relaxes,  the  abdominal  muscles  contract,  and  thus  an  antagonizing  force 
is  originated  which  tends  to  expel  the  air.  In  this  the  elasticity  of  the 
lungs  and  of  the  walls  of  the  thorax  itself  affords  a  great  assistance. 
Owing  to  Jhis  elasticity,  the  muscular  exertion  required  for  the  introduc- 
tion of  the  air  greatly  exceeds  that  required  for  its  expulsion. 

In  tranquil  respiration,  we  may  regard  the  changing  of  the  air  to  be 
accomplished  by  the  alternate  depression  and  elevation  of  the  diaphrag- 
matic floor  of  the  chest.  On  an  average,  this  takes  place  1 7  times  in  a 
minute,  and  in  an  adult  of  the  standard  size  we  may  assume  that  17 
cubic  inches  of  air  are  introduced  at  each  inspiration.  Of  every  five 
breaths  one  is  usually  deeper  than  the  other  four.  The  statement  often 
made,  that  five  pulsations  correspond  to  one  respiration,  must  be  received 
with  a  certain  restriction.  In  pneumonia,  the  respirations  may  be  to 
the  pulsations  as  1  to  2  ;  in  typhoid  fevers,  as  1  to  8 ;  and  even  in  a 
state  of  health  there  may  be  considerable  variations. 

By  muscular  movements,  which  thus  call  into  action  atmospheric  pres- 
sure, the  air  is  drawn,  but  not  forced,  into  the  respiratory  apparatus. 
Considering,  however,  the  solid  contents  of  the  lungs,  which  can  not  be 
taken  at  less  than  200  cubic  inches,  it  is  clear  that  the  amount  is  not 
more  than  sufficient  to  fill  the  nasal  passages,  the  trachea,  and  the  larger 
ramifications  of  the  bronchial  tubes.  Lying  nearest  to  the  outlet,  it 
would  be  the  first  to  be  expelled  by  the  act  of  expiration.  There  could 
be  no  exchange  of  the  fresh  for  the  foul  air,  unless  some  additional  means 
were  employed  for  accomplishing  its  transference  from  the  larger  ramifi- 
cations of  the  bronchial  tubes  to  the  remotest  air-cells. 

2d.  The  transference  of  fresh  air  to  the  cells  is  accomplished  by  re- 
sorting to  two  different  principles,  the  diffusion  of  free  gases  into  one  an- 
other, and  muscular  contraction. 

An  estimate  of  the  relative  share  which  each  of  these  takes  is  arrived 
Effect  of  gase-  at  by  an  examination  of  the  absolute  velocity  with  which 
Us^oforganic  Sases  diffuse  into  one  another.  The  statement  that  gases 
muscle  fibres,  act  as  vacua  to  each  other  has  led  to  some  very  erroneous 


PASSAGE  OF  OXYGEN  TO  THE   BLOOD.  163 

conclusions.  It  has  "been  taken  for  granted  that  the  actual  diffusion  is 
very  rapid,  perhaps  approaching  to  the  velocity  with  which  gases  rush 
into  a  void.  But  I  have  shown*  that  this  is  altogether  a  misconception, 
and  that  the  transit  of  fresh  air  from  the  bronchi,  exchanging  with  foul 
air  from  the  cells,  if  conducted  on  that  principle  alone,  would  require  a 
period  greatly  beyond  the  time  occupied  for  one  respiratory  act,  which  is 
about  three  seconds  and  a  half. 

To  an  additional  agent  we  must  therefore  look  for  a  complete  explana- 
tion, and  this,  I  think,  is  presented  in  the  circular  organic  fibres  of  the 
bronchial  tubes  and  cells.  It  has  long  been  understood  that  these  pos- 
sess the  power  of  varying  the  capacity  of  the  tubes. 

With  this  agency  in  view,  this  second  stage  of  the  process  is  accom- 
plished as  follows :  The  carbonic  acid,  vapor  of  water,  and  excess  of  ni- 
trogen, if  any,  that  have  accumulated  in  the  cells  belonging  to  any  given 
bronchial  tree,  are  expelled  therefrom  by  the  muscular  contraction  of  the 
circular  organic  fibres,  and  are  delivered  into  the  larger  bronchial  tubes, 
in  which  diffusion  at  once  takes  place  with  the  air  just  introduced.  As 
soon  as  the  expiration  is  completed,  relaxation  of  the  muscular  fibres  oc- 
curs, and  the  passages  and  cells  dilating,  both  through  their  own  elastic- 
ity and  the  exhaustive  effect  arising  from  the  simultaneous  contraction  of 
other  bronchial  trees,  fresh  air  is  drawn  into  them,  the  alternate  expulsion 
and  introduction  being  accomplished  by  muscular  contraction  and  elas- 
ticity, the  different  bronchial  trees  coming  into  action  at  different  periods 
of  time,  some  being  contracting  while  others  are  dilating. 

3d.  The  third  stage  is  the  passage  of  oxygen  from  the  cells  to  the  blood: 
it  is  through  the  wall  of  the  cell,  the  wall  of  the  blood-vessel,  Passage  of  ox- 
and  the  sac  of  the  blood  disc.  The  carbonic  acid  issues  from  £gen  thr°ush 

the  membranes 

the  plasma,  and  passes  through  the  wall  of  the  blood-vessel  to  the  blood. 
and  the  wall  of  the  cell. 

Many  physiologists  have  supposed  that  this  exchange  of  oxygen  for 
carbonic  acid  takes  place  on  the  principle  of  diffusion.  On  Exchan  e  of 
the  authority  of  Valentin  and  Brunner,  it  has  been  asserted  carbonic  acid 
that  the  proportional  exchange  actually  observed  is  1174  of 
oxygen  for  1000  of  carbonic  acid,  these  being  the  theoretical  quantities 
under  the  law  of  diffusion ;  but  there  is  no  difficulty  in  proving  that  this 
is  a  physical  impossibility,  for  the  exchange  is  not  merely  that  of  oxy- 
gen and  carbonic  acid;  it  is  much  more  complicated.  The  lungs  regu- 
late the  quantity  of  free  nitrogen  in  the  system,  and  there  is  a  constant 
escape  of  the  vapor  of  water.  These  bodies,  moreover,  are  not  present- 
ed in  the  gaseous  state,  but  in  that  of  liquid  solution ;  and  the  wall  of 
the  cell,  of  the  pulmonary  capillary,  and  of  the  blood  disc,  by  their  con- 
densing action,  totally  disturb  the  conditions  of  diffusion. 
*  American  Journal  of  Med.  Sciences,  April,  1852. 


164  ESCAPE   OF   CARBONIC   ACID   FROM   THE   BLOOD. 

If  an  aqueous  film,  not  more  than  three  eighths  of  a  millionth  of  an  inch 
in  thickness,  can  completely  disturb  the  law  of  diffusion  by  the  condens- 
ing action  it  exerts  on  carbonic  acid  and  oxygen,  what  may  be  expected 
from  the  moist  walls  of  the  air-cells  and  pulmonary  artery,  which  con- 
jointly must  be  more  than  a  thousand  times  as  thick  ? 

From  these  complications,  it  is  not  possible  to  assign  any  definite  ratio 
as  expressing  the  gaseous  exchange  between  the  interior  of  the  cells  and 
the  blood,  for,  so  far  from  this  being  a  case  of  exchange  between  two  gas- 
es without  any  obstruction  intervening,  the  condition  under  which  alone 
the  law  of  diffusion  applies,  the  nitrogen  is  doubtless  in  a  state  of  solu- 
tion in  the  blood,  the  steam  in  the  liquid  condition  of  water ;  and  re- 
specting the  carbonic  acid,  nothing  certain  is  known  whether  it  be  in  so- 
lution or  chemically  combined.  Perhaps  it  is  united  with  soda  in  the 
blood  as  a  bi-carbonate.  From  this  latter  substance  hydrogen  gas  will 
expel  one  half  of  its  carbonic  acid,  and  in  like  manner  a  stream  of  hy- 
drogen gas  passed  through  blood  deprived  of  its  fibrin  removes  carbonic 
acid.  Upon  such  principles  it  has  been  supposed  that  atmospheric  oxy- 
gen removes  carbonic  acid  from  the  blood  during  respiration,  just  as  would 
a  stream  of  hydrogen  rernove  half  the  acid  from  a  solution  of  bi-carbon- 
ate of  soda. 

The  generation  of  carbonic  acid  in  the  system  is  commonly  localized 
Place  of  the  ^y  referring  it  to  the  soft  tissues.  But,  though  doubtless 
generation  of  much  originates  in  this  way,  as  is  illustrated  by  the  case  of 
Cld'  insects,  in  which  the  air  is  carried  directly  to  the  parenchyma 
of  the  organs  without  the  intervention  of  any  proper  oxidizing  blood, 
there  can  be  no  doubt  that  in  man,  as  in  all  the  higher  tribes,  a  very 
large  proportion  is  generated  in  the  blood  itself.  If  there  were  no  other 
reason  to  bring  us  to  this  conclusion,  it  would  be  sufficient  to  recall  that 
ultimate  oxidation  by  no  means  occurs  at  6nce,  but  that  the  various 
wasted  products  pass  from  stage  to  stage  in  their  retrograde  career. 
Thus,  between  the  syntonin  of  muscular  fibre  and  the  urea  of  the  urine, 
many  steps  or  stages  intervene,  and  that  much  of  these  changes  is  ac- 
complished in  the  blood  itself  is  demonstrated  by  what  occurs  in  the 
use  of  excesses  of  starch,  albumen,  or  gelatine  in  the  food.  Such  sub- 
stances, finding  access  through  the  absorbents  in  a  modified  form,  but  not 
wanted  for  the  repair  of  any  part,  are  dismissed  without  ever  entering 
into  the  composition  of  any  organ,  by  the  lungs  or  the  kidneys  as  prod- 
ucts of  oxidation  or  derivatives  thereof. 

The  act  of  respiration  in  man  is  therefore  accomplished  in  the  follow- 
Generai  state-  ing  way.  The  air,  introduced  by  atmospheric  pressure, 
process  of  res-  brought  into  play  by  the  action  of  the  diaphragm  and  other 
piration.  respiratory  muscles,  fills  the  nasal  passages,  the  trachea,  and 

larger  ramifications  of  the  bronchial  tubes.  Between  it  and  the  gas 


GENERAL   STATEMENT   OF   THE   KESPIEATOEY   ACT.  165 

coming  from  the  pulmonary  vesicles,  diffusion  steadily  takes  place,  tend- 
ing to  remove  the  cell  gas  into  the  atmosphere;  but  this  gas  is  not 
brought  from  the  vesicles  by  diffusion  alone,  which  could  not  act  with 
sufficient  speed,  but  by  the  contraction  of  the  circular  organic  muscles  of 
the  bronchial  tubelets  and  of  the  cells,  the  different  bronchial  trees  not 
acting  simultaneously,  but  successively.  As  soon  as  contraction  is  over, 
the  tubes  expand  by  their  elasticity,  and  the  air  is  drawn  into  the  cells, 
each  bronchial  tree,  by  its  contraction,  aiding  the  expansion  of  the  adja- 
cent ones.  The  lungs  are  therefore  not  altogether  passive  during  respi- 
ration, as  is  sometimes  said.  The  exchange  between  the  gas  in  the  cells 
and  that  in  the  blood  does  not  take  place  through  simple  diffusion,  or  in 
quantities  proportional  to  the  diffusion  volumes  of  oxygen  and  carbonic 
acid.  It  is  a  complex  diffusion,  in  which  the  disturbances  arise  from  the 
gases  in  the  blood  being  either  dissolved  or  combined,  and  through  sev- 
eral intervening  membranes,  that  of  the  air-cells,  that  of  the  pulmonary 
artery,  and  that  of  the  blood  disc,  all  of  which  exert  a  condensing  action, 
of  the  result  of  which  it  is  impossible  to  furnish  any  numerical  estimate. 
The  process  ends  by  the  expulsion  of  the  foul  air  which  has  accumulated 
in  the  larger  bronchi  and  trachea,  by  the  diminution  which  takes  place 
in  the  capacity  of  the  chest  during  expiration,  occasioned  by  the  contrac- 
tion of  the  expiratory  muscles,  the  elasticity  of  the  walls  of  the  chest, 
and  of  the  lungs  themselves. 

Such  is  the  arrangement  by  which  fresh  air  is  constantly  presented  to 
the  blood,  and  the  gases  and  vapors  exhaling  from  it  are  removed.  The 
degree  of  exhaustion  occurring  in  the  chest  scarcely  justifies  the  ex- 
pression sometimes  used,  "a  tendency  to  a  vacuum,"  since  it  is  rarely 
more  than  competent  to  raise  water  a  single  inch.  This  may  be  readily 
proved  by  dipping  a  glass  tube,  open  at  both  ends,  and  half  an  inch  in 
diameter,  into  a  cup  of  water,  and  placing  the  projecting  extremity  be- 
tween the  lips,  taking  care  to  keep  the  muscles  of  the  mouth  at  complete 
rest.  It  will  then  be  seen  that  at  each  inspiration  the  water  rises  about 
an  inch,  and  at  each  expiration  is  depressed  to  a  similar  extent.  Its 
movements  indicate  the  degree  of  rarefaction  or  compression  occurring  in 
the  chest. 

It  has  been  found  convenient  to  consider  the  gaseous  contents  of  the 
lungs  under  several  different  titles :   1st.  The  residual  air  is  Divisions  of 
that  portion  which  can  not  be  removed  by  the  most  power-  content,e(ofStiie 
fill  expiration ;  2d.  The  supplemental  air  remains  after  tran-  lungs. 
quil  respiration,  but  can  be  removed  at  will ;  3d.  The  breathing  or  tidal 
air  is  that  portion  which  changes  by  tranquil  inspiration  and  expiration ; 
4th.  The  complemental  air  is  that  which  can  be  inhaled  by  the  deepest 
inspiration,  over   and   above   that   introduced  by  ordinary  breathing. 
These  are  terms  introduced  by  Mr.  Jeffreys. 


166 


VOLUME   AND   CHANGES   OF   THE    GAS. 


"The  amount  of  air  that  can  be  expelled  by  the  deepest  expiration 
Connection  be-  after  the  fullest  inspiration"  bears  a  singular  relation  to  the 
tiIneandPira~  heiSlli  of  the  individual,  as  was  discovered  by  Dr.  Hutch- 
height,  inson.  "  For  every  inch  of  stature  from  five  to  six  feet, 
eight  additional  cubic  inches  of  air  at  60°  Fahr.  may  be  thus  given  out." 
The  quantity  of  air  which  can  be  thus  expelled  for  the  stature  of  five  feet 
one  inch  is  174  cubic  inches,  and  for  six  feet,  262.  It  is  independent  of 
the  absolute  capacity  of  the  chest. 

The  diurnal  amount  of  air  introduced  into  the  lungs  has  been  variously 
Volun-  and  estimated  from  226  to  399  cubic  feet.  A  part,  from  4  to  6 
changes  of  the  per  cent.,  of  the  oxygen  thus  introduced  disappears  in  the 
respired  gas.  JUngs,  anci  the  expired  air  is  charged  with  from  3  to  5  per 
cent,  of  carbonic  acid.  But  that  nothing  analogous  to  combustion  occurs 
in  those  organs  is  proved  by  their  temperature,  which  is  not  higher  than 
that  of  other  parts  of  the  system.  Moreover,  carbonic  acid  can  be  with- 
drawn from  venous  blood  in  a  Torricellian  vacuum,  and  still  better  by 
agitating  the  blood  with  such  gases  as  hydrogen  and  nitrogen,  proving 
that  that  gas  pre-exists  in  the  venous  blood  before  its  entiy  into  the 
lungs,  and  is  not  formed  in  those  organs,  unless,  indeed,  it  exists  as  a  bi- 
carbonate, as  already  mentioned.  The  quantity  of  carbonic  acid  thus 
disengaged  is  less  than  the  quantity  of  oxygen  absorbed,  because  much 
of  the  latter  is  consumed  in  the  production  of  sulphuric  and  phosphoric 
acids,  which  escape  in  the  urinary  secretion,  as  indeed  does  a  large  quan- 
tity of  carbonic  acid  itself. 

The  experiments  of  Vierordt  show  that  the  expiration,  in  a  state  of 
Vierordt's  rest,  contains  4.334  per  cent,  of  carbonic  acid;  that,  as  the 
experiments,  number  of  respirations  per  minute  increases,  the  percentage 
amount  of  carbonic  acid  diminishes  ;  and  that  for  every  expiration,  with- 
out reference  to  its  duration,  there  is  a  constant  amount  of  carbonic  acid, 
namely,  2.5  per  cent.,  to  which  we  must  add  a  second  value,  expressing 
the  quantity  of  carbonic  acid,  and  which  is  exactly  proportional  to  the 
duration  of  the  respiration,  as  is  shown  in  the  following  table. 


Eespirations 
per  minute. 

Percentage  of 
carbonic  acid. 

Constants. 

Augmentation  of  the  percentage 
of  the  carbonic  acid  for  the 
duration  of  the  respiration. 

6 
12 
24 

48 
96 

5.7 
4.1 
3.3 
2.9 

2.7 

2.5 
2.5 
2.5 
2.5 
2.5 

3.2 
1.6 
0.8 
0.4 
0.2 

Vierordt  also  estimates  that,  for  the  entire  removal  of  the  carbonic 
acid  from  the  blood,  more  than  three  hundred  respiratory  acts  per  minute 
would  be  required.  To  some  extent,  the  depth  of  the  respiration  will 
compensate  for  want  of  frequency.  Thus  he  shows  that  in  an  expiration 
of  double  the  usual  volume,  the  quantity  of  carbonic  acid  removed  is 


RATIO   OF   INSPIRED   AND   EXPIRED   OXYGEN.  167 

nearly  equal  to  that  which  would  be  exhaled  by  respirations  of  three 
times  the  normal  frequency,  and  on  examining  a  single  respiration,  he 
demonstrates  what,  however,  would  obviously  be  foreseen  from  a  consid- 
eration of  the  circumstances  of  the  case,  that  the  last  portions  of  the  ex- 
piration are  the  richest  in  carbonic  acid.  Thus  the  first  half  of  a  respi- 
ration contained  only  3.72  per  cent,  of  carbonic  acid,  the  last  half  5.44 
per  cent.. 

With  respect  to  the  ratio  between  the  quantity  of  oxygen  inspired  and 
that  contained  in  the  expired  carbonic  acid,  a  variation  will  Katiooflhein 
be  observed,  depending  on  many  conditions,  as,  for  example,  spired  and  ex- 
on  the  nature  of  the  food.  Thus,  with  a  carbohydrate,  the  pired  oxygen' 
quantity  of  oxygen  in  the  carbonic  acid  will  always  be  less  than  that  in- 
spired, a  portion  being  employed  in  the  destruction  of  the  systemic  nitro- 
genized  material  which  is  undergoing  decay.  This  destruction  of  nitro- 
genized  material  is  not  sufficient  for  the  support  of  animal  heat,  and 
hence  either  carbohydrates  introduced  by 'the  food,  or  fat  already  exist- 
ing in  the  system,  must  be  resorted  to  for  the  purpose  of  making  up  the 
deficiency.  With  such  variations  in  the  requirements  of  the  system, 
and  variations  in  the  nature  of  the  food,  the  ratio  of  the  oxygen  intro- 
duced to  that  in  the  carbonic  acid  removed  must  also  vary. 

For  the  perfect  oxidation  of  the  different  elements  of  food,  very  differ- 
ent quantities  of  oxygen  are  required ;  thus,  for  the  oxidation  of  100 
parts  of  fat,  it  would  require  292.14  of  oxygen;  for  that  of  starch,  118.52; 
for  that  of  muscle,  147.04. 

For  reasons  to  be  considered  when  we  treat  of  the  production  of  heat, 
the  quantity  of  carbonic  acid  disengaged  varies  with  external  Variations  in 
circumstances.     When  the  weather  is  cold  it  is  greater  than  the  respired 
when  it  is  warm.     Thus  at  68°  there  is  twice  as  much  lib-  air' 
erated  as  at  106°.     It  increases  during  exercise  and  after  eating,  but 
diminishes  during  sleep.     More  is  set  free  by  men  than  by  women ;  it 
also  varies  with  age,  the  proportion  rising  from  eight  years  to  thirty,  re- 
maining stationary  to  forty,  and  then  declining.     It  changes  with  the 
frequency  of  the  respirations.     The  total  quantity  of  carbon  daily  re- 
moved by  respiration  may  be  estimated  at  eight  ounces. 

Besides  the  carbonic  acid  removed,  a  large  quantity  of  water  is  ex- 
creted by  the  lungs,  for  the  expired  air  may  be  regarded  as  Water  removed 
saturated,  or  containing  the  maximum  quantity  of  water  for  in  »espiration. 
94°.  For  the  vaporization  of  this  water  much  heat  is  consumed,  as  is 
likewise  the  case  for  the  warming  of  the  introduced  air,  which,  no  mat- 
ter wha"t  the  external  temperature  may  have  been,  is  brought  to  that  of 
the  lungs. 

With  respect  to  the  absolute  amount  of  air  expired,  and  also  the  quan- 
tity of  water  removed  by  the  lungs,  some  experiments  have  recently  been 


168  QUANTITY   OF   AIR   AND   WATER. 

made  by  my  son,  Dr.  J.  C.  l)raper ;  the  principle  upon  which  they  were 
Quantit  of  air  con(lucted  may  be  thus  briefly  stated.  The  air  from  the 
expired  per  lungs,  which  has  a  dew-point  of  94°,  was  passed  by  a  wide 
tube  through  a  metallic  condenser  kept  at  32°,  care  being 
taken  to  have  as  little  obstruction  as  possible  to  its  egress.  The  weight 
of  the  water  collected  in  the  condenser  furnished  the  means  of  calculating, 
by  a  simple  formula,  the  quantity  of  air  which  had  been  expired,  for  the 
vapor,  leaving  the  respiratory  passages  at  94°,  and  that  leaving  the  con- 
denser at  32°,  were  at  their  maximum  densities.  Computations  exe- 
cuted upon  data  obtained  on  this  principle  furnish  the  following,  among 
other  interesting  results : 

1.  On  making  sixteen  respirations  in  the  minute,  and  continuing  the 
experiment  for  twenty  minutes,  the  average  of  five  different  series  of  ex- 
periments gives  622  cubic  inches  of  air  expired  each  minute. 

2.  On  making  six  respirations  in  a  minute,  and  continuing  the  trial 
for  twenty  minutes,  the  average  of  three  series  of  experiments  gives  511 
cubic  inches  for  the  air  expired  each  minute. 

3.  On  making  thirty-three  respirations  in  a  minute,  and  continuing  the 
experiment  for  twenty  minutes,  the  average  amount  of  air  is  1077  cubic 
inches  for  the  air  expired  in  each  minute. 

On  comparing  these  three  statements,  it  appears  that,  the  first  repre- 
senting normal,  the  second  very  slow,  the  third  very  quick  respiration, 
the  absolute  amount  of  air  removed  from  the  lungs  is  directly  proportion- 
al to  the  number  of  respiratory  acts  in  a  given  period  of  time,  and  this 
notwithstanding  such  variations  in  the  depth  of  the  inspirations  as  un- 
der such  circumstances  are  likely  to  occur. 

With  respect  to  the  quantity  of  water  removed  from  the  lungs,  he  also 
shows, 

Quantit  of  wa        ^'  1^ia*'  at  an  atmospheric  temperature  of  55°,  the  dew- 
ter  exhaled  per  point  being  49°,  the  number  of  expirations  sixteen  per  minute, 
the  quantity  of  water  removed  per  minute  is  4.416  grains. 

5.  The  other  conditions  remaining  the  same,  but  the  respirations  re- 
duced to  six  per  minute,  the  amount  of  water  removed  per  minute  is 
3.586  grains. 

6.  The  other  conditions  remaining  as  before,  but  the  number  of  res- 
pirations increased  to  thirty-three  per  minute,  the  amount  of  water  re- 
moved p'er  minute  is  7.560  grains. 

From  these  statements  it  therefore  appears  that  the  quantity  of  water 
removed  from  the  blood  by  respiration  increases-  with  the  frequency  of 
the  respiratory  acts,  and  this  notwithstanding  variations  which,  under 
such  circumstances,  must  take  place  in  their  depth.  Theoretically,  it  is 
also  obvious  that  the  absolute  amount  thus  expired  is  dependent  on  the 
existing  dew-point  of  the  air.  In  the  general  table,  given  on  page  15, 


EFFECT  OF  RESPIRATION  ON  THE  BLOOD.          169 

the  amount  of  water  is  calculated  from  Seguin's  experiments,  but  it  ap- 
pears from  these  results,  which  are  obtained  by  a  much  more  accurate 
process,  that  the  number  there  given  is  undoubtedly  too  high. 

The  time  of  exposure  of  the  blood  to  the  air  is  only  a  second  or  two. 
The  color  changes,  as  has  been  described  before,  from  blue  to  crimson, 
and  the  temperature  rises  a  degree  or  two,  as  is  shown  by  an  examina- 
tion of  the  left  cavities  of  the  heart.  The  water  thus  removed  is  not 
pure,  but  contains  animal  matter  in  a  state  of  decay. 

Though  we  have  treated  of  the  act  of  respiration  as  consisting  of  two 
separate  and  consecutive  stages,  inspiration  and  expiration,  Respiration  is 
in  reality  it  proceeds  continuously.  At  the  respiratory  sur- 
face,  which  is  the  wall  of  the  air-cell,  the  passage  of  oxygen  ing. 
inward,  and  of  carbonic  acid  and  steam  outward,  takes  place  in  a  steady 
and  unvarying  manner.  The  periodicity  under  which  it  has  been  conven- 
ient to  speak  of  this  function  concerns  only  the  introduction  and  removal 
of  gases  from  the  large  air-ways. 

Considering,  therefore,  the  continuous  loss  of  water  which  the  venous 
blood  brought  by  the  pulmonary  arterial  branches  undergoes,  Effect  of  respi- 
it  must  give  rise  necessarily  to  a  greater  density  in  the  blood 
on  the  left  side  as  compared  with  that  of  the  right  side  of  blood, 
the  heart.  The  total  quantity  of  blood  passing  through  the  lungs  in  one 
minute  is  225  ounces,  and  the  loss  of  water  from  this  in  the  same  time 
can  not  be  more  than  7  grains.  This,  therefore,  shows  that  the  actual 
loss  of  water  by  the  blood  during  its  passage  over  the  air-cells  is  about 
15^QO  part,  a  quantity  which  is  altogether  inappreciable,  so  far  as  its  in- 
fluence on  the  specific  gravity  is  concerned,  and  showing  us  that  the  ob- 
servations which  some  experimenters  have  made  on  this  point,  with  a 
view  of  demonstrating  an  increased  spissitude,  density,  or  cohesiveness 
of  the  blood  on  the  left  side  of  the  heart,  from  the  giving  up  of  its  water 
as  it  passed  through  the  respiratory  organ,  are  either  exaggerated  or  af- 
fected by  some  deceptive  cause. 

The  introduction  of  an  irrespirable  gas  into  the  lungs,  or  the  prevention 
of  the  access  of  the  atmosphere,  brings  the  circulation  of  the  Effect  of  the  in- 
blood  to  a  stop ;  for  that  movement  depends,  as  I  have  shown, 
on  the  aeration  taking  place  in  the  pulmonary  capillaries.  In  gases. 
such  cases  there  will  be  an  engorgement  of  the  right  heart  and  vessels 
arising  therefrom,  but,  if  the  stoppage  has  not  lasted  too  long,  the  current 
may  be  re-established  by  re-establishing  the  respiration.  Death  com- 
monly ensues  on  an  exclusion  of  the  air  for  five  minutes,  and,  in  cases 
of  drowning,  it  is  rare  for  restoration  to  be  effected  if  the  immersion  has 
lasted  more  than  four. 

In  the  respiration  of  protoxide  of  nitrogen,  a  gas  which  is  an  energetic 
supporter  of  combustion,  and  acting  more  powerfully  on  the  animal  sys- 


Fig.  81. 


170  EXPERIMENTS   OF   REGNAULT   AND   EEISET. 

Effect  of  rot  tem  wnen  respire(l  tnan  even  oxygen  itself,  on  account  of  its 
oxide  of  nitro-  ready  condensibility  by  pressure,  or  by  membranes,  and  sol- 
ubility in  water,  the  circulation  is  greatly  quickened  at  first, 
and  a  state  of  exhilaration  ensues  ;  but  this  is  soon  followed  by  a  con- 
dition of  depression,  or  even  of  coma,  for  the  quantity  of  carbonic  acid 
produced  in  the  system  is  now  so  great  that  the  lungs  are  wholly  inade- 
quate to  effect  its  removal,  and  all  the  symptoms  of  poisoning  by  car- 
bonic acid  come  on. 

Zimmerman  found  that  a  rabbit  exhaled  12  J  grains  of  carbonic  acid 
per  hour  when  breathing  atmospheric  air,  but  that  the  quantity  rose  at 
once  to  20  grains  per  hour  when  it  was  caused  to  breathe  protoxide  of 
nitrogen.  But  by  far  the  most  complete  and  important  series  of  experi- 
Summary  of  ments  yet  made  in  regard  to  the  relations  of  the  aerial  me- 
Regnauit's  and  dium  and  the  respiring  animal  is  that  of  MM.  Eegnault  and 
iments  or;  res-  Reiset,  published  in  the  Annales  de  Chimie,  Juillet,  1849,  of 
piration.  which,  since  it  may  be  taken  as  a  model  of  physiological  in- 

vestigation, a  brief  abstract  is  here  given. 

The  apparatus  they 
employed  is  represented 
in  Fig.  81.  It  possesses 
the  great  advantage  over 
all  experimental  arrange- 
ments heretofore  employ- 
ed in  permitting  an  ani- 
mal to  be  kept  even  for 
many  days  in  a  limited 
volume  of  air,  but  under 
such  circumstances  that 

Experiments  on  respiration.  that     ail*    WaS     Constantly 

kept  at  its  normal  composition  by  the  automatic  motions  of  the  instru- 
ment itself:  oxygen  being  thus  furnished  as  it  was  required,  and  car- 
bonic acid  removed. 

The  arrangement  consists  of  three  parts  :  1st,  a  chamber  or  bell,  Z,  for 
inclosing  the  animal,  surrounded  by  a  jar  filled  with  water,  the  tempera- 
ture of  which  could  be  ascertained  by  a  thermometer,  L  In  the  interior 
of  the  bell  was  a  platform  perforated  with  holes,  by  the  aid  of  which  the 
'excretions  could  be  collected.  On  one  side,  at^>,  was  a  pressure  gauge, 
connected  with  the  bell  by  a  tube,  and  showing  the  condition  of  conden- 
sation or  rarefaction  of  the  included  atmosphere.  2d.  At  the  same  side, 
the  bell  communicated,  by  means  of  India-rubber  tubes,  m,  n,  with  two 
cylindric  vessels,  q,  r,  filled  with  a  solution  of  caustic  potassa,  and  which 
were  driven  by  the  aid  of  powerful  clock-work  in  such  a  way  that  the 
one  alternately  rose  and  the  other  descended,  the  flexible  tube  s  permit- 


EXPEEIMENTS  OF  EEGNAULT  AND  EEISET.  171 

ting  this  motion.  The  result  of  this  was  that  a  portion  of  the  air  of  the 
bell  was  alternately  drawn  into  each  of  the  cylindric  vessels,  its  carbon- 
ic acid  removed  by  the  potash,  and  then  it  was  returned ;  so,  as  fast  as 
the  animal  produced  that  gas  by  breathing,  the  potash  removed  it,  giving 
rise,  therefore,  to  a  tendency  to  a  certain  amount  of  rarefaction  in  the  air 
of  the  bell ;  but,  3d,  on  the  opposite  side  of  the  bell  were  placed  three 
receptacles,  e,  e',  e",  filled  with  pure  oxygen  gas,  which  flowed  into  the 
bell  through  the  tubes  fh,  fh,  f'h,  to  compensate  for  that  rarefaction, 
coming  in  by  a  bubble  at  a  time  through  the  little  potash  flask  i,  the 
oxygen  being  pressed  out  of  the  reservoirs  by  a  solution  of  chloride  of 
calcium  descending  through  a  stop-cock,  c,  from  a  reservoir,  b  b',  kept  at 
a  constant  level  in  the  usual  manner  by  the  flasks  a,  a',  a".  As  fast  as 
one  receptacle  was  exhausted,  the  pressure  tube  was  successively  con- 
nected with  the  others,  and  so  the  supply  kept  up.  Attached  to  the 
stand  supporting  the  animal  was  a  eudiometer,  o,  which  enabled  a  small 
quantity  of  air  to  be  withdrawn  from  the  bell  at  any  moment  for  the 
purpose  of  analytical  examination.  For  other  details  of  this  apparatus, 
and  the  particulars  of  its  method  of  use,  reference  may  be  made  to  the 
original  memoir  itself.  It  is  sufficient  for  the  present  purpose  to  under- 
stand that  an  animal  could  be  kept  in  the  interior  of  this  bell  for  several 
days  without  showing  any  signs  of  discomfort,  pure  oxygen  being  sup- 
plied to  it,  and  the  carbonic  acid  produced  by  breathing  removed  by  the 
play  of  the  machine  itself. 

The  following  is  an  abstract  of  the  results  obtained : 

1st.  Hot-blooded  animals,  mammalia  and  birds,  under  their  ordinary 
diet,  always  disengage  a  little  nitrogen  by  respiration,  the  Hot  blooded 
amount  varying  from  less  than  y-J-^-  to  jfe  of  the  weight  of  animals  on  an 
the  oxygen  they  consume. 

2d.  When  these  animals  are  fasting,  they  often  absorb  nitrogen  in  pro- 
portions similar  to  the  preceding.     In  like  manner,  an  absorp-  The  same 
tion  of  nitrogen  was  observed  after  starving  the  animal,  and  then  fasting. 
submitting  him  to  a  diet  very  different  from  his  ordinary  one,  and  also 
during  sickness. 

3d.  The  ratio  between  the  quantity  of  oxygen  contained  in  the  car- 
bonic acid  and  the  quantity  consumed  depends  more  on  the  Influence  of 
nature  of  the  food  than  on  the  class  to  which  the  animal  be-  food  and  fast- 
longs,  being,  when  the  animals  are  starving,  the  same  as  it  is  ing* 
when  they  are  fed  upon  meat,  or  perhaps  a  trifle  less.  From  this  the 
interesting  conclusion  may  be  drawn  that  a  starving  animal  furnishes  to 
the  air  of  respiration  his  own  substance,  which  is  of  course  of  the  same 
nature  as  the  flesh  he  eats  when  dieted  on  meat.  All  hot-blooded  ani- 
mals present,  when  they  are  starving,  the  respiration  of  carnivora.  The 
ratio  for  the  same  animal  varies  from  0.62  to  1.04,  according  to  the  na- 
ture of  the  diet. 


172  EXPEEIMENTS   OF   REGNAULT   AND   EEISET. 


4th.  In  fowls,  submitted  to  their  usual  diet  of  grain,  there  is  often 
Respiration  more  oxygen  in  the  carbonic  acid  disengaged  than  was  furnished 
of  birds.  jn  fnc  air  }^y  respiration.  The  surplus  of  course  comes  from 
the  food. 

5th.  The  quantity  of  oxygen  consumed  in  a  given  time  varies  with 
f  the  state  of  digestion,  motion,  and  other  circumstances.  Com- 
motion, age,  pared  together,  the  consumption  is  greater  among  the  young 
than  among  adults,  greater  among  those  that  are  lean  but  in 
good  health  than  among  those  that  are  fat. 

6th.  If  we  take  an  equal  weight  of  the  animals  under  examination,  the 
influence  of  quantity  of  oxygen  varies  much  with  their  absolute  size ; 
the  size  of  ani-  thus  it  is  ten  times  greater  among  little  birds,  such  as  spar- 
rows and  green-finches,  than  among  common  fowls.  This 
is  owing  to  the  fact  that,  since  these  different  species  have  the  same  tem- 
perature, and  the  little  ones  present  relatively  a  greater  surface  to  the 
ambient  air,  they  must  consume  relatively  more  oxygen  to  keep  up  their 
heat  to  the  standard  degree. 

7th.  Hibernating  animals,  such  as  marmots,  when  perfectly  awake,  ex- 
Res  iration  of  ^ibit  no  peculiarity,  but  when  fast  asleep  often  absorb  nitro- 
hibemating  gen.  The  ratio  of  the  oxygen  contained  in  the  carbonic  acid 
to  that  inspired  is  very  low,  scarcely  amounting  to  0.4,  the 
missing  oxygen  escaping  in  the  compounds  of  the  urinary  secretion ; 
but  since  this  removal  takes  place  only  periodically,  the  sleeping  marmot 
exhibits  the  remarkable  phenomenon  of  increasing  in  weight  by  respira- 
tion alone. 

8th.  The  consumption  of  oxygen  by  sleeping  marmots  is  very  small, 
scarcely  -^  of  what  they  require  when  awake.  At  the  moment  they 
awaken  from  their  lethargy,  their  respiration  becomes  extremely  active, 
and  during  the  period  of  their  awakening  they  consume  much  more  oxy- 
gen than  when  they  are  completely  awake.  Their  temperature  rises  rap- 
idly, and  their  members  gradually  lose  their  stiffened  state.  While  tor- 
pid they  can  remain  without  difficulty  in  an  atmosphere  which  would 
suffocate  them  in  a  few  moments  if  awake. 

9th.  Cold-blooded  animals,  for  an  equal  weight,  consume  much  less 
Res  iration  of  oxygen  *nan  hot-blooded.  Frogs  with  their  lungs  cut  out 
cold-blooded  continue  to  breathe  with  nearly  the  same  activity  as  before, 
often  living  for  several  days,  the  proportions  of  the  gases 
absorbed  and  disengaged  differing  little  from  what  is  observed  in  the 
case  of  uninjured  frogs.  This  shows  that  their  respiration  can  be  con- 
ducted by  the  skin.  The  respiration  of  earthworms  is  the  same  as  that 
of  frogs,  as  regards  the  quantity  of  oxygen  consumed,  when  they  are  com- 
pared under  an  equal  weight. 

10th.  The  respiration  of  insects,  such  as  May-bugs  and  silk-worms, 


NERVES   OF   RESPIRATION.  •     173 

is  much  more  active  than  that  of  reptiles.  Under  an  equal  Respiration  of 
weight  they  consume  nearly  as  much  oxygen  as  mammalia :  insects- 
the  comparative  lowness  of  their  temperature  is  due  to  the  relatively 
great  surface  and  moist  exterior  they  present  to  the  air.  It  is  to  be  re- 
marked that  we  are  here  comparing  the  respiration  of  insects  with  that 
of  mammalia  whose  weights  may  lie  from  2000  to  10,000  times  as 
great. 

llth.  The  respiration  of  animals  of  different  classes,  in  an  air  con- 
taining two  or  three  times  as  much  oxygen  as  the  atmos-  Effect  of  in- 
phere,  does  not  differ  from  existing  respiration ;  indeed,  the  creasins  tj6 
animals  do  not  appear  to  perceive  that  they  are  in  a  medium  ygen. 
different  from  the  ordinary  atmosphere. 

12th.  The  respiration  of  animals  in  a  medium  in  which,  for  the  most 
part,  hydrogen  replaces  the  nitrogen  of  our  atmosphere,  scarcely  differs 
from  existing  respiration ;  only  there  is  remarked  a  greater  consumption 
of  oxygen,  due  perhaps  to  the  necessity  of  compensating  for  the  increased 
cooling  arising  from  the  contact  of  hydrogen  gas. 

The  introduction  of  air  into  the  system  is,  to  a  certain  extent,  auto- 
matic, and,  to  a  certain  extent,  dependent  on  the  will.  In  tranquil  res- 
piration we  are  wholly  unconscious  of  the  motion ;  the  ex-  Nerves  in 
citing  impression  is  made  on  the  pneumogastric  nerves,  and,  voived  in  re& 
being  conveyed  to  the  respiratory  ganglion,  the  medulla  ob-  piratlon- 
longata,  is  there  so  reflected  that  through  the  agency  of  the  phrenic  nerve 
motion  takes  place  in  the  diaphragm.  The  automatic,  and  therefore  un- 
conscious movement,  to  a  certain  extent,  occurs  in  that  way.  But  there 
is  no  doubt  that  the  brain  also  participates  in  the  function.  No  other 
evidence  of  this  is  required  than  that  we  can  "  hold  the  breath,"  and  the 
relative  share  that  the  voluntary  and  automatic  mechanisms  take  is  illus- 
trated by  the  circumstance  that  this  holding  of  the  breath  can  only  be 
persisted  in  for  a  certain  time,  when  the  necessity  for  respiring  becomes 
altogether  uncontrollable. 

It  is  not,  however,  to  be  supposed  that  so  important  a  condition  as 
that  of  the  introduction  of  the  air  is  only  slenderly  provided  for.  Many 
other  nerves,  besides  those  mentioned,  take  part  in  it  directly  or  indi- 
rectly ;  the  fifth  pair,  the  nerves  of  the  general  surface,  and  also  the  great 
sympathetic,  the  intercostals,  the  spinal  accessory,  which  probably  gives 
its  motor  property  to  the  pneumogastric.  Opinion  has  differed  respect- 
ing the  cause  which  produces  the  necessary  impression  on  the  receiving 
nerves,  some  referring  it  to  the  presence  of  venous  blood  in  the  capilla- 
ries of  tke  lungs,  and  some  to  the  carbonic  acid  in  the  cells.  Moreover, 
there  is  reason  to  believe  that  the  presence  of  an  abnormal  amount  of 
venous  blood  in  the  respiratory  ganglions  will  of  itself  give  rise  to  res- 
piratory movements  through  the  proper  centrifugal  nerves. 


174     •  RESULTS   OF   RESPIRATION. 


The  control  possessed  by  the  will  over  the  introduction  of  air  stands 
Respiration  in  a  close  relation  to  the  production  of  articulate  or  other 
tar^and^art-  soun^s»  an^  therefore  to  intercommunication  between  indi- 
ly  automatic,  viduals  by  speech.  This  involves  not  merely  a  general  con- 
trol alone,  but  also  a  particular  one,  which  is  reached  by  regulating  the 
movements  of  the  glottis  by  the  agency  of  the  superior  and  inferior  laryn- 
geal  nerves.  But  though  the  will  for  these  important  purposes  exercises 
so  marked  a  power  of  regulation,  it  is  to  be  looked  upon  as  superadded 
or  incidental,  and  during  sleep,  coma,  and  that  larger  portion  of  life  which 
is  spent  in  total  inattention  to  the  carrying  on  of  this  function,  it  is  dis- 
charged in  a  purely  automatic  way. 

The  mechanism  which  accomplishes  the  surprising  results  of  respira- 
Results  of  res-  tion  may  therefore  well  challenge  our  admiration.  As  a 
piration.  self-acting  or  automatic  contrivance,  over  which  we  have  not 
a  necessary  control,  it  originates  in  a  single  year  nearly  nine  millions  of 
separate  motions  of  breathing.  It  never  fatigues  us ;  indeed,  we  are 
never  conscious  of  its  action.  In  the  same  time,  a  hundred  thousand 
cubic  feet  of  air  have  been  introduced  and  expelled,  and  more  than  thir- 
ty-five hundred  tons  of  blood  have  been  aerated.  In  a  future  page  we 
shall  have  to  present  the  wonderful  mechanism  by  which  aerial  currents, 
as  they  pass  in  and  out  of  the  respiratory  apparatus,  are  incidentally  em- 
ployed as  a  means  of  producing  musical  notes  or  articulate  sounds,  and 
of  thus  establishing  a  relation  and  communication  between  different  in- 
dividuals. By  these  the  feelings  and  thoughts  are  diffused,  and  in  a 
mechanical  origin  commence  those  bonds  which  hold  society  together. 


ANIMAL  HEAT.  175 


CHAPTER  X. 

OF  ANIMAL   HEAT. 

Participation  of  Organic  Forms  in  external  Variations  of  Temperature. — Mechanism  for  counter* 
balancing  these  Variations. — Development  of  Heat  in  Plants  at  Germination  and  Inflorescence. 
— Its  Cause  is  Oxidation. —  Connection  of  Respiration  and  Heat. — Temperature  of  Man. — His 
Power  of  Resistance. — The  diurnal  Variations  of  Heat. —  Connection  of  these  Variations  with 
organic  Periodicities. — Annual  Variations  of  Heat. — Control  over  them  by  Food,  Clothing,  and 
Shelter. — Source  of  Animal  Heat. — Effect  of  Variations  in  the  Food  and  in  the  respired  Me- 
dium, both  as  respects  its  Nature  and  Rarefaction. — Hybernation. — Starvation. — Artificial  Re- 
duction of  Temperature  by  Blood-letting. — Principles  of  Reduction  of  Temperature. — Radia- 
tion.—  Contact. — Evaporation. —  Their  Balance  with  the  Heating  Processes. — Local  Varia- 
tions eliminated  by  the  Circulation. —  Control  by  the  Nervous  System. — Its  physical  Nature. — 
Allotropism  of  Organic  Bodies.  » 

OWING  to  the  earth's  diurnal  rotation  on  its  axis,  and  its  annual  move- 
ment of  translation  round  the  sun  in  an  orbit  inclined  to  the  ,7  . 

Variations  of 

equator,  variations  of  temperature  arise,  the  vicissitudes  of  external  tem- 
summer  and  winter,  day  and  night.  perature. 

In  these  variations  all  objects  upon  the  surface  of  the  planet  partici- 
pate ;  organic  forms  are  no  exception.  As  the  heat  of  the  medium  in 
which  they  live  ascends  or  descends,  theirs  follows  it  at  a  rate  depend- 
ent on  their  conductibility. 

Like  mineral  substances,  the  more  lowly  forms  of  life  submit  to  these 
changes.     They  have  no  provision  for  check  or  compensation.  Organic  forms 
In  summer,  the  temperature  of  the  stem  of  a  tree  rises  with-  t^0^-^.111 
out  any  restraint;  in  winter  it  declines;   and,  should  the  tions. 
point  be  reached  at  which  those  nutritive  changes  that  give  motion  to  the 
sap  cease,  nothing  is  done  to  arrest  the  descent,  and  the  whole  organism 
passes  into  a  state  of  torpor,  hybernation,  or  temporary  death. 

Now,  since  this  following  of  atmospheric  temperatures  must  take  place 
in  every  organism  as  well  as  in  every  mineral  body,  the  con-  Compensating 
struction  of  one  having  a  uniform  mode  of  existence  in  all 
climates  and  all  seasons  implies  a  resort  to  some  subsidiary  tribes. 
mechanism,  which,  though  it  may  not  check,  may  yet  compensate  for 
these  vicissitudes.  Accordingly,  so  nearly  is  this  equalization  accom- 
plished in  the  highly-developed  tribes,  and  a  standard  temperature  so 
nearly  attained  for  them,  that  many  physiologists,  misled  by  imperfect 
observations,  have  concluded  that  such  living  beings  are  emancipated  by 
nature  from  the  operation  of  physical  laws  :  an  erroneous  conclusion,  for 
in  them  that  action  is  only  concealed. 


176  THE   HEAT   OF   PLANTS. 

In  different  races,  the  mechanism  by  which  these  variations  of  atmos- 
pheric temperature  are  balanced  acts  with  different  degrees  of  perfection, 
d  hot  ^n  ^s  a  subdivision  has  been  founded,  and  animals  classi- 
Mooded  ani-  fied  as  the  cold  and  hot  blooded.  We  are  not,  however,  to 
mals-  attach  much  importance  to  such  an  arrangement :  it  is  rather 

imaginary  than  founded  on  any  real  distinction.  In  man,  the  tempera- 
ture is  near  100°  ;  in  fishes,  it  is  about  that  of  the  water  in  w^hich  they 
live.  Insects,  in  their  larva  and  pupa  condition,  are  cold-blooded;  in 
their  perfect  condition,  hot. 

We  have  now  to  explain  what  physical  principles  are  resorted  to  in 
solving  the  problem  of  maintaining  an  organic  form  at  a  constant  tem- 
perature in  a  medium  the  heat  of  which  is  variable ;  and  as  we  may 
reasonably  anticipate  that  these  principles  are  the  same  in  every  tribe  of 
life,  it  will  facilitate  our  investigations  to  commence  with  the  simplest 
cases  first. 

There  are  two  periods  in  the  life  of  a  plant  during  which  it  simulates 
Two  periods  of  the  functions  of  an  animal  in  ^maintaining  a  temperature 
heat  in  plants,  higher  than  that  of  the  surrounding  air.  These  periods  are, 
1st,  at  the  germination  of  the  seed ;  2d,  during  the  functional  activity  of 
the  flower. 

If  a  mass  of  seeds  be  laid  together,  as  in  the  making  of  malt,  the  op- 
Heat  of  germ-  eration  being  conducted  at  a  gentle  temperature,  and  with  the 
ination.  access  of  atmospheric  air,  oxygen  disappears,  carbonic  acid  is 

set  free,  and  the  temperature  rises  forty  or  fifty  degrees.  A  process  of 
oxidation  must  therefore  have  been  carried  into  effect,  and  to  it  we  trace 
the  heat  disengaged,  for  carbon  can  not  produce  carbonic  acid  without  a 
rise  of  temperature  ensuing.  The  loss  of  weight  which  a  seed  exhibits 
is  therefore  due  to  its  loss  of  carbon,  and  the  whole  effect  is  explained  in 
the  statement  that  atmospheric  oxygen  has  united  with  a  portion  of  car- 
bon contained  in  the  seed,  producing  carbonic  acid  gas  and  an  evolution 
of  heat. 

Again,  during  flowering,  the  same  action  is  repeated.  The  flower  re- 
Heat  of  inflo-  moves  from  the  surrounding  air  a  portion  of  the  oxygen  it 
rescence.  contains,  and  replaces  it  with  carbonic  acid,  the  temperature 
rising,  as  accurate  experiments  have  proved,  in  absolute  correspondence 
with  the  quantity  of  oxygen  consumed.  Nor  is  this  elevation  insignifi- 
cant. A  mass  of  flowers  has  been  observed  to  raise  the  thermometer  from 
66°  to  121°. 

If  thus  the  disengagement  of  warmth  is  the  result  of  oxidation,  it  must 
Oxidation  the  depend  on  the  presence  of  air,  and  be  regulated  by  the  rapidity 
e^vation^of6  wit^  which  oxygen  can  be  supplied.  As  we  pass  from  the 
temperature,  consideration  of  plants  to  that  of  animals,  we  discover  that  the 
production  of  heat  must  be  connected  with  the  power  and  precision  with 


CONNECTION  OF  RESPIKAT10N  AND   HEAT.  177 

which  the  respiratory  apparatus  works,  for  it  is  through  its  agency  that  air 
is  introduced.  Extensive  observation  accordingly  establishes  a  close  cor- 
respondence in  each  animal  tribe  between  the  quantity  of  heat  produced  and 
the  capability  of  respiratory  apparatus.  The  lower  tribes  breathe  sfbw- 
ly  and  are  cold.  Earthworms  are  only  a  degree  or  two  warmer  than  the 
ground ;  and  even  among  vertebrates,  fishes  are  only  two  or  three  degrees 
warmer  than  the  water,  a  lowness  of  temperature  in  a  great  ^measure  de- 
pending on  the  high  cooling  agencies  which  that  liquid  ex-  Connection  of 
erts,  its  specific  heat,  and  the  facility  with  which  currents  are  respiration  and 
established  in  it.  However,  even  in  these  cases  the  produc-  L 
tion  of  heat  depends  on  the  power  of  the  respiratory  engine.  The  bonito 
can  keep  its  heat  20°  above  that  of  the  sea,  and  the  narwhal  maintains 
a  steady  temperature  at  96°. 

The  organic  operations  involved  in  nutrition,  and  also  the  retrograde 
changes  of  decay,  can  only  go  on  at  their  accustomed  rates  so  invariability 
long  as  standard  limits  of  temperature  are  observed.     The  of  organic  ac- 

„    ,  .  m-f    •        T  T         "OT  implies  a 

proper  progress  of  the  actions  of  life  implies  a  corresponding  definite  tem- 
adjustment  of  heat,  and  this  irrespective  of  the  mere  size  of  Perature- 
the  animal.  Even  those  that  are  microscopic  must  come  under  this  rule. 
When  the  temperature  of  a  liquid  containing  infusorials  is  caused  to  de- 
scend to  the  freezing  point  gradually,  the  last  portions  which  solidify  are 
those  which  surround  each  of  these  little  forms  ;  a  drop  is  kept  liquid  by 
the  heat  they  disengage.  In  the  same  individual,  the  absolute  tempera- 
ture will  depend  on  its  respiratory  condition ;  thus  insects,  in  passing 
through  each  of  their  stages  of  metamorphosis,  present  a  definite  condi- 
tion as  to  their  heat:  the  larva  of  the  bee  may  be  only  two  degrees  above 
the  air,  while  the  perfect  insect  is  10°.  Whatever  accelerates  the  in- 
troduction and  expulsion  of  the  air,  increases  the  warmth;  Variations  of 
so  a  bee  shaken  in  a  bottle,  and  kept  in  a  state  of  constant  ^0^0*  ™d£ 
muscular  exertion,  will  raise  the  temperature  contained  there-  tion. 
in  far  higher  than  if  he  remains  inactive.  Among  insects,  those  having 
the  largest  organs  of  respiration  have  always  the  highest  temperature ; 
and,  since  muscular  motion  implies  destruction  of  muscular  tissue  by  ox- 
idation, and  therefore  development  of  heat,  we  should  expect  to  find,  as 
is  actually  the  case,  that  animals  possessing  the  highest  powers  of  loco- 
motion will  possess  also  the  highest  temperature.  Of  all,  therefore,  birds, 
the  endurance  and  energy  of  whose  powers  of  flight  result  from  the  per- 
fection of  their  respiratory  mechanism,  have  the  highest  temperature.  It 
is  about  110°.  Yet  even  here  there  are  differences  :  the  sluggish  barn- 
door fowl  has  not  the  heat  of  the  energetic  swallow. 

The  standard  temperature  of  man  is  usually  stated  to  be  98°,  but  from 
this  mean  it  ranges  within  certain  limits  upward  and  down.  Temperature 
Much  depends  on  the  state  of  the  health;  of  course,  every  thing  of  man- 

M 


178  DIUENAL   VAEIATIONS   OF   HEAT. 

on  the  respiration.  In  fevers  it  will  rise  to  105° ;  in  tetanus  it  may  reach 
110°;  the  contrary  in  asthma,  when  it  may  sink  to  82°,  owing  to  imper- 
fect access  of  air ;  in  cyanosis  to  77°,  owing  to  imperfect  aeration  of  the 
blood ;  in  Asiatic  cholera  to  75°,  owing  to  the  non-reception  of  oxygen  by 
the  cells  in  their  diseased  state.  It  also  varies  with  the  period  of  life : 
in  the  new-born  infant  it  is  100° ;  it  presently  sinks  to  99°,  and  rises 
during  childhood  to  102°.  Mental  exercise  in  the  adult  increases  it, 
bodily  exertion  still  more.  The  special  degree  varies  with  the  point  on 
which  the  observation  is  made :  the  limbs  are  colder  than  the  trunk,  and 
this  is  the  more  marked  as  the  point  is  more  remote.  On  the  leg  the 
temperature  may  be  93°  ;  on  the  sole  of  the  foot,  90°  ;  while  that  of  the 
viscera  is  101°. 

In  his  residence  in  different  climates,  man  is  exposed  to  variations  of 
Resistance  of  temperature  which  extend  over  a  scale  of  200°.  Toward 

1  anHrTtT  e°x"  ^  P°*GS  ^  co^  °^  winter  ^s  °^ten  —  60°  ;  in  the  tropics 
tremes  of  tem-  the  heat  of  summer  +130°.  For  a  short  period  his  power  of 
perature.  resistance  is  greatly  beyond  what  these  numbers  would  in- 
dicate; he  can  enter  with  impunity  an  oven  heated  to  600°,  provided  the 
air  is  dry.  In  these  cases,  though  excessive  evaporation  from  the  skin 
moderates  the  effect  and  keeps  it  within  bounds,  there  is  always  a  mark- 
ed rise  of  temperature  of  the  whole  body.  In  a  corresponding  manner, 
exposure  to  cold  produces  depression,  as  shown  in  Dr.  Davy's  observa- 
tions. At  92°  of  the  air,  a  thermometer  under  the  tongue  stood  at  100  J° ; 
at  73°  it  stood  at  99°  ;  at. 60°  it  stood  at  97J0. 

Among  these  variations  there  is  one  class  which  calls  for  critical  at- 
Diurnal  varia-  tenti°n-  I*  ^  the  diurnal  variation ;  less  marked  in  man, 
tion  in  the  heat  who  instinctively  makes  provision  against  it,  but  well  shown 
in  the  case  of  fasting  animals.  This  illustrates,  in  an  inter- 
esting manner,  the  controlling  influence  of  external  conditions  ;  for  if  ex- 
posure to  a  high  temperature,  as  that  of  an  oven,  compels  a  ^rise  of  the 
heat  of  the  whole  body,  in  spite  of  the  conservative  arrangements,  and 
exposure  to  extreme  cold  compels  a  descent,  we  ought  to  expect  that  ex- 
posure to  more  moderate  degrees  would,  in  like  manner,  produce  an  im- 
pression. 

The  old  astrologers  were  therefore  not  altogether  wrong  when  they  af- 
firmed the  doctrine  of  planetary  influences.  The  diurnal  temperatures 
of  a  locality,  as  dependent  on  the  position  of  the  sun,  are  expressed  in 
the  system  of  man.  The  minimum  of  heat  for  the  night,  and  the  max- 
imum for  the  day,  find  a  correspondence  in  the  decline  of  animal  temper- 
ature at  the  former,  and  its  rise  at  the  latter  period.  The  experiments 
of  M.  Chossat  on  birds  submitted  to  absolute  starvation  showed  that, 
though  in  their  normal  state,  at  the  commencement,  the  variation  between 
midnight  and  noon  was  only  1J°,  it  gradually  increased  to  6°,  until  at 


CALORIFIC  INFLUENCE  OF  FOOD.  179 

last,  the  generation  of  heat  wholly  ceasing,  the  temperature  gave  way 
rapidly  just  previous  to  death. 

If,  therefore,  it  was  possible  for  life  to  continue  without  the  evolution 
of  animal  heat,  it  would  be  with  the  body  as  it  is  with  the  stem  of  a  tree. 
It  would  follow  the  thermometric  variations  in  the  air,  the  maxima  of 
heat  and  cold  being  somewhat  later  than  the  aerial  ones,  and  within  nar- 
rower limits,  by  reason  of  the  low  conducting  power.  The  nearest  ap- 
proach to  this  is  in  cases  of  absolute  starvation,  and  though  in  man  the 
effect  is  masked  by  the  due  taking  of  food,  it  none  the  less  exists.  In 
human  communities  there  is  some  reason  beyond  mere  cus-  influence  of 
torn  which  has  led  to  the  mode  of  distributing  the  daily 
meals.  A  savage  may  dispatch  his  gluttonous  repast,  and  ature. 
then  starve  for  want  of  food ;  but  the  more  delicate  constitution  of  the 
civilized  man  demands  a  perfect  adjustment  of  the  supply  to  the  wants 
of  the  system,  and  that  not  only  as  respects  the  kind,  but  also  the  time. 
It  seems  to  be  against  our  instinct  to  commence  the  morning  with  a 
heavy  meal.  We  break  fast,  as  it  is  significantly  termed,  but  we  do 
no  more,  postponing  the  taking  of  the  chief  supply  until  dinner,  at  the 
middle  or  after  part  of  the  day.  If  men  were  only  guided  by  views  of 
economy  of  time  saved  for  the  pursuits  of  business,  or  if,  on  this  occasion, 
they  put  in  practice  the  rule  they  observe  on  so  many  others,  of  never 
postponing  the  gratification  of  their  desires,  the  first  affair  of  the  morn- 
ing would  have  been  an  abundant  repast.  But  against  this  something 
within  us  revolts,  and  that  in  all  classes,  the  laboring,  the  intellectual, 
the  idle.  I  think  there  are  many,  reasons  for  supposing,  when  we  recall 
the  time  which  must  elapse  between  the  taking  of  food  and  the  comple- 
tion of  respiratory  digestion,  that  this  distribution  of  meals  is  not  so 
much  a  matter  of  custom  as  an  instinctive  preparation  for  the  systemic 
rise  and  fall  of  temperature  attending  on  the  maxima  and  minima  of  daily 
heat.  The  light  breakfast  has  a  preparatory  reference  to  noonday,  the 
solid  dinner  to  midnight. 

Once  more  I  would  remark,  that  we  must  not  be  deceived  by  the 
masked  aspect  which  the  system  in  this  matter  presents,  connection  of 
Its  diurnal  variations  are  concealed  by  agencies  brought  variations  of 

.  „      .  £        ,  iL    L-ut  •  j.    •      heat  with  or- 

specially  into  operation  for  that  purpose,  but  they  exist  in  ganic  periodi- 
the  physical  necessities  of  the  case ;  and  herein,  I  believe,  cities- 
we  have  a  first  glimpse  of  the  cause  of  those  periodicities,  which  physi- 
cians from  the  earliest  times  have  remarked ;  for,  though  the  nervous 
system,  both  in  a  state  of  health  and  disease,  may  seem  to  be  their  ori- 
gin, it  is  not  impossible  that  its  changes  are  connected  with  variations 
thus  taking  place  in  the  external  world. 

We  have  next  to  consider  the  effect  of  the  annual  varia-  Annual  varia- 
tions of  temperature,  which  reach  their  maximum  soon  after  tions  of  heat- 


180          EFFECT  OF  ANNUAL  VARIATIONS  OF  HEAT. 

mid-summer  and  their  minimum  soon  after  mid- winter,  the  manner  in 
which  the  system  comports  itself  under  them,  and  the  means  which  in- 
stinct and  experience  teach  us  to  employ  in  providing  against  them. 

The  tables  of  mortality  show  that  there  is  a  loss  of  life  at  the  annual 
imu  rnaximum  and  minimum  of  temperature  which  greatly  ex- 
ai  variations  ceeds  the  average  of  any  other  period.  In  England  and  Bel- 
gium, where  the  mean  temperature  of  the  summer  months  is 
moderate,  this  is  not  so  strikingly  marked  for  those  months,  and  the  chief 
loss  falls  upon  the  winter ;  but  in  New  York,  which  has  a  summer  cor- 
responding to  that  of  the  south  of  Europe  and  a  winter  like  that  of  the 
north,  the  effect  of  these  extremes  becomes  so  obvious  as  even  to  be 
popularly  connected  with  the  position  of  the  thermometer  above  or  below 
55°.  Among  infants  and  the  aged,  whose  controlling  powers  over  tem- 
perature are  imperfect,  these  effects  are  most  distinctly  witnessed ;  but 
among  healthy  adults,  and  even  in  Europe,  we  can  detect  them  on  crit- 
ical examination.  Thus,  in  Brussels,  the  monthly  mortality  for  January 
being  taken  as  105,  that  for  July  is  91,  for  August  96,  and  for  October 
93 ;  and  it  is  to  be  recollected  that  these  are  the  residual  traces  of  the 
operation  of  cold  and  heat  after  all  the  precautions  have  been  used  to 
ward  them  off.  I  might  make  here  the  same  remark  that  was  made 
when  considering  diurnal  variations,  that  the  true  effect  is  so  masked  and 
concealed  that  we  are  liable  to  undervalue  it,  and  do  not  properly  appre- 
ciate this  tax  put  upon  the  system. 

These  annual  variations  of  external  temperature  are  chiefly  combated 
Control  over  ty  food,  clothing,  and  shelter.  The  dietetic  changes  we  make 
annual  varia-  between  winter  and  summer  are  founded  upon  the  principle 

tions  by  food,         -    '  .  ,          .-ri    ./•  -  i  -    •  1*       j»  -11 

clothing,  shel-  of  using  more  combustible  food  for  the  former,  and  less  com- 
bustible for  the  latter  season ;  and,  since  the  calorific  ef- 
fect of  an  article  of  food  greatly  depends  on  the  quantity  of  oxidizable 
hydrogen  it  contains,  the  winter  diet  has  more  of  that  element  than  the 
.summer.  Partly  thus  by  varying  the  nature,  and  partly  by  varying  the 
quantity  of  the  food,  we  can  effect  a  compensation  to  a  certain  extent. 

Of  the  manner  in  which  the  diet-compensation  is  aided  by  variations 
in  clothing  little  needs  to  be  said.  The  experiments  of  Count  Eumford 
established  the  fact  that  the  conductibility  of  summer  clothing  is  greater 
than  that  of  winter,  and  therefore  its  resistance  to  the  escape  of  heat  is 
less.  It  is  sufficient  merely  to  allude  to  the  control  which  is  gained  by 
difference  of  thickness  in  the  garments,  and  by  their  amount  or  quan- 
tity. We  instinctively  make  these  adjustments  to  meet  the  existing  ex- 
igencies, and,  as  far  as  may  be,  in  this  manner  aim  at  a  medium  effect. 

The  check  upon  external  temperature  by  the  use  of  clothing  was  doubt- 
less one  of  the  first  contrivances  of  the  human  race.  Even  of  savage  life 
it  is  a  cardinal  feature.  The  check  by  adjustment  of  diet  belongs  to  a 


IMPERFECTIONS  OF  SHELTER.  181 

civilized  state,  since  it  implies  a  certain  control  over  the  animal  appetite 
and  personal  self-denial.  Though  great  improvements  in  both  of  these 
will  doubtless  hereafter  be  made,  when  the  principles  of  their  operation 
-are  more  generally  and  better  understood,  they  must,  even  in  their  pres- 
ent condition,  be  regarded  as  having  reached  a  higher  perfection  than  the 
check  by  resorting  to  shelter.  The  art  of  constructing  dwelling-houses 
may  be  said  to  be  yet  in  its  infancy  in  all  parts  of  the  world,  E  .  . 
and  yet  in  no  particular  is  the  physical  condition  of  females  perfections  of 
and  children,  and  especially  of  the  sick,  more  nearly  touched.  shelter- 
It  is  only  within  our  own  times  that  attention  has  been  drawn  to  the 
proper  methods  for  the  admission  of  warmth,  and  air,  and  light ;  the  hy- 
gienic influences  of  furniture  and  decoration  are  unknown,  beyond,  per- 
haps, a  popular  impression  that  it  is  unhealthy  to  be  in  a  recently-paint- 
ed apartment,  inexpedient  to  sleep  in  a  chamber  where  there  are  flowers, 
and  unpleasant  in  summer  to  have  a  carpet  on  the  floor,  because  it  looks 
warm,  and  is  thought  to  generate  dust.  The  owner  of  a  palace,  on  which 
wealth  has  been  fruitlessly  lavished,  finds,  on  a  cold  day,  that  he  can 
not  obtain  from  his  parlor  fire  the  necessary  warmth  unless  by  alternate- 
ly turning  round  and  round.  The  testy  valetudinarian  sits  in  his  easy- 
chair,  tormented  by  drafts  coming  in  from  every  quarter.  In  his  vain 
attempts  to  stop  the  offending  crevices,  it  never  occurs  to  him  that  his 
chimney  is  a  great  exhausting  machine,  which  is  drawing  the  air  out  of 
the  room,  and  that  his  means  of  warming  and  ventilation  are  the  most 
miserable  that  could  be  resorted  to,  since  radiation  can  warm  only  one 
side  of  a  thing  at  a  time,  and  fresh  air  under  those  conditions  can  only 
be  introduced  by  drafts. 

To  warm  rooms  by  contrivances  such  as  the  open  fire-place  or  stove 
is  obviously  unphilosophical,  since  the  effect  of  these  is  to  ex-  of  artificial 
haust  the  air  of  the  apartment.  The  modern  method  of  warm-  warmth, 
ing  by  furnaces,  which  act  by  throwing  air  duly  moistened  and  of  the 
right  temperature  into  the  rooms,  and  therefore  by  condensation,  is  clear- 
ly a  better  system,  since  it  not  only  puts  an  end  to  all  drafts,  the 
tendency  being  to  force  air  out  through  every  crevice  instead  of  drawing 
it  in,  but  it  possesses  the  inappreciable  advantages  of  giving  uniformity 
of  warmth,  a  perfect  control  over  the  degree  of  heat,  and  likewise  over  the 
nature  of  the  air,  which  need  not  be  drawn  from  the  cellar,  or  the  con- 
taminated impurity  of  the  street,  but  by  suitable  flues  from  the  free  and 
clear  air  above.  Ventilating  contrivances  which  can  cheaply  and  effectu- 
ally force  a  supply  of  artificially  cooled  air  in  the  summer,  and  warm  air 
in  the  winter,  into  dwelling-houses,  are  still  a  great  desideratum. 

By  the  aid  of  diet,  clothing,  and  shelter,  we  are  able  to  effect  an  almost 
complete  compensation  for  the  changes  of  diurnal  and  annual  temper- 
atures, and  even  to  occupy  any  climate  of  the  globe.  It  is  the  manage- 


182  EFFECT  OF  COMBUSTIBLE  ALIMENT. 

ment  of  caloric  which  makes  man  what  he  is,  and  constitutes  his  special 
prerogative ;  his  degree  of  skill  therein  is  the  measure  of  his  civilization. 
The  distribution  of  plants  and  animals,  or,  rather,  their  limitation  within 
fixed  boundaries,  depends  on  the  distribution  of  heat,  but  from  these  re- 
straints man  is  free,  because  he  can  control  temperatures. 

From  these  considerations  of  the  effect  of  external  heat  on  the  human 
mechanism,  we  return  to  a  more  critical  examination  of  the  modes  by 
which  heat  is  generated,  and  its  degree  regulated  in  the  body. 

In  every  instance  we  assert  that  the  production  of  animal  heat  is  due 
Source  of  ani-  to  oxidation  taking  place  in  the  economy,  and  giving  rise  to 
mal  heat.  carbonic  acid,  water,  and  other  collateral  products.  It  is  not 
necessary  to  attach  any  weight  to  the  experiments  of  Dulong,  which  seem- 
ed to  indicate  that  not  more  than  four  fifths  of  the  heat  actually  pro- 
duced could  be  owing  to  the  oxidation  of  carbon,  nor  to  those  of  a  like 
kind  of  Despretz.  The  method  they  resorted  to  for  the  measurement  of 
the  disengaged  heat  was  open  to  error ;  the  numbers  they  employed  as 
representing  the  combustion  heats  were  incorrect ;  nor  did  they  make  any 
allowance  for  other  substances,  such  as  sulphur  and  phosphorus,  which 
are  simultaneously  oxidizing,  and  the  products  of  their  combustion  escap- 
ing by  the  kidneys. 

Eeduced  to  its  ultimate  conditions,  the  evolution  of  animal  heat  de- 
Effect  of  more  pends  on  the  reaction  taking  place  between  the  air  intro- 
aiSient^w^ai-  ^uce^  ^7  respiration  and  the  food,  and  as  either  one  or  other 
cohoi.  of  these  is  touched,  the  result  may  be  predicted.  If,  for  ex- 

ample, into  the  digestive  canal  alcoholic  preparations  be  introduced,  they 
are  absorbed,  by  reason  of  their  liquid  condition  and  diffusibility,  with 
readiness.  The  combustibility  of  alcohol,  and  the  amount  of  heat  it 
yields,  are  so  great,  that  the  primary  effect  of  the  oxidation  which  ensues 
is  a  warmth  or  feverish  sensation.  By  reason  of  the  changes  which  are 
now  taking  place  so  actively  in  it,  the  blood  circulates  with  unwonted 
rapidity,  and  the  supply  to  the  brain  increasing,  that  organ  exhibits  an 
unusual  functional  activity.  But  this  display  of  intellection  is  only  tem- 
porary, and  an  opposite  condition  soon  comes  on,  for,  more  carbonic  acid 
accumulating  in  the  blood  than  the  lungs  can  get  rid  of,  the  depressing 
effects  of  that  body  commence,  and  eventually  the  symptoms  of  poison- 
ing by  it  ensue. 

Not  unlike  this  is  the  train  of  effects  which  arise  when,  instead  of  va- 
Effectofamore  rying  the  nature  of  the  article  ingested,  we  vary  that  of  the 
porter  of  respi-  &as  respired.  An  energetic  supporter  of  combustion,  like  the 
ration  than  air.  protoxide  of  nitrogen,  gives  rise  to  a  feverish  glow,  cerebral 
activity,  to  be  followed  eventually  by  a  deep  depression,  the  poisonous 
influence  of  the  carbonic  acid  produced  being  exhibited.  After  a  while 
the  system  casts  it  off,  and  recovers  its  condition  of  health  completely. 


EFFECT  OF  RAREFIED  AIR.  183 

If  there  be  an  abstinence  from  food,  since  the  introduction  of  air  by 
respiration  goes  on  without  abatement,  the  body  itself  must  A  starvin 
undergo  oxidation,  lose  weight,  and  emaciation  occur.     Its  imai  dies  of 
tendency  to  follow  the  diurnal  variations  of  temperature  be-  c 
come  more  and  more  strikingly  marked  as  the  process  of  starvation  goes 
on,  and  finally  a  rapid  and  unchecked  decline  of  the  heat  ensues.     Yet 
even  then  life  may  be  preserved  by  the  application  of  sufficient  external 
warmth,  and  from  an  extreme  condition  of  attenuation  an  animal  may  be 
rescued  by  the  use  of  food ;  but  for  such  a  recovery  the  external  warmth 
must  be  continued  until  there  has  been  time  for  digestion  and  absorption 
to  take  place.     If,  however,  such  an  extraneous  aid  be  not  duly  applied, 
the  temperature  of  the  starving  animal  goes  on  diminishing,  and  he  dies 
of  cold. 

The  doctrine  we  are  here  inculcating,  that  animal  heat  is  due  to  oxida- 
tion in  the  system,  is  still  further  strikingly  illustrated  by  Effectofre. 
what  might  be  termed  starving  the  respiration.  As  cold  is  spiring  rarefied 
felt  from  want  of  food,  so  also  it  is  from  want  of  air.  In  as-  air' 
cending  high  mountains,  the  effect  upon  the  system  has  been  graphically 
expressed  as  "  a  cold  to  the  marrow  of  the  bones ;"  a  difficulty  of  making 
muscular  exertion  is  experienced ;  the  strongest  man  can  scarcely  take  a 
few  steps  without  resting;  the  operations  of  the  brain  are  interfered  with ; 
there  is  a  propensity  to  sleep.  The  explanation  of  all  this  is  very  clear. 
In  the  accustomed  volume  of  air  received  at  each  inspiration,  there  is  a 
less  quantity  of  oxygen  in  proportion  as  the  altitude  gained  is  higher. 
Fires  can  scarce  be  made  to  burn  on  such  mountain-tops ;  the  air  is  too 
thin  and  rare  to  support  them  ;  and  so  those  combustions,  which  should 
go  on  at  a  measured  rate  in  the  interior  of  the  body,  are  greatly  re- 
duced in  intensity,  and  hence  the  sense  of  a  penetrating  cold.  Such 
journeys,  moreover,  illustrate  how  completely  the  action  of  the  muscular 
system,  and  also  of  the  brain,  is  dependent  on  the  introduction  of  air ; 
and  under  the  opposite  condition  of  things,  where  men  descend  in  diving- 
bells,  though  surrounded  by  the  chilly  influences  of  the  water,  they  ex- 
perience no  corresponding  sensation  of  cold,  because  they  are  breathing  a 
compressed  and  condensed  atmosphere. 

The  respiratory  apparatus  of  certain  animals  permits  a  reduction  in  the 
amount  of  air  introduced  under  exposure  to  a  due  degree  of  _,, 

.  fo  Phenomena  of 

cold.      Such  animals  are  said  to  hybernate.     At  the  com-  hybemating 
ing  on  of  winter  their  adipose  tissues  are  engorged  with  fat.  animals- 
As  they  pass  into  their  annual  sleep,  the  rate  of  their  respiration  falls. 
The  marmot,  which  in  activity  will  make  140  respirations  in  a  minute, 
makes  now  but  3  or  4;  the  temperature  of  the  body  descends,  and  combus- 
tion of  the  store  of  fat  goes  on  more  slowly.     Yet  it  does  go  on,  for,  toward 
spring,  the  animal  has  become  very  lean ;  sufficient  heat  is  disengaged  to 


184  COOLING   AGENCIES. 

permit  the  blood  slowly  to  circulate,  and  so  "barely  to  keep  up  the  func- 
tions of  life.  If,  however,  the  stock  of  material  available  for  combustion 
is  insufficient,  the  animal  dies. 

Although  we  can  not  interfere  with  the  rate  of  respiration,  we  can 
Reduction  of  affect  the  quantity  of  air  introduced  into  the  system  by  arti- 
temperatureby  £cial  means,  as  in  the  operation  of  blood-letting ;  for  though, 

blood-letting  '  r 

and  in  morbid  alter  Diooa  nas  been  drawn,  we  may  make  the  normal  mini- 
states.  ker  of  respirations,  17  in  a  minute,  and  for  each  introduce 
17  cubic  inches  of  air,  we  have  diminished  the  number  of  discs,  which 
are  the  carriers  of  oxygen ;  and,  as  the  experience  of  physicians  in  all 
times  has  shown,  there  is  no  method  so  effectual  in  reducing  any  unusual 
or  febrile  temperature.  So,  in  like  manner,  in  Asiatic  cholera,  the  marble 
coldness  which  the  body  presents  is  attributable  to  the  loss  of  function 
of  the  discs,  and  the  consequent  abatement  in  the  quantity  of  oxygen  in- 
troduced. 

Thus  far  we  have  considered  the  means  which  the  animal  mechanism 
,,  ,  .  '  possesses  for  raising  its  own  temperature ;  it  remains  to  show 
reducing  the  how  it  can  also  regulate  it.  For  any  thing  that  has  thus  far 
are*  been  said  to  the  contrary,  the  combustions  or  oxidations 
which  are  continually  going  forward  should  establish  a  constant  rise,  and 
there  must  therefore  be  some  principle  of  restraining  such  a  rise  within 
due  bounds.  Considering  also  the  incessant  vicissitudes  of  atmospheric 
temperature,  a  constant  degree  could  not  be  maintained  unless  the  sys- 
tem possessed  the  means  of  depressing  as  well  as  elevating  its  heat. 

That  the  means  of  regulating  the  heat  are  purely  physical,  we  should 
Effect  of  cov-  expect  for  many  very  obvious  reasons.  Economy  of  heat  is 
s'ecte^onduct-  accomplished  by  non-conducting  material.  On  this  princi- 
ibiiity.  pie,  hair,  wool,  and  feathers  act  by  excluding  the  contact  of 

the  atmosphere,  their  low  conductibility  being  brought  into  operation. 
In  many  cases,  the  manner  in  which  this  is  done  is  clearly  intentional. 
Thus  the  down  which  is  placed  on  the  breast  of  a  water-fowl  is  to  screen 
off  the  chilling  influence  of  the  water,  which  is  there  chiefly  felt  as  the 
bird  swims  on  the  surface.  The  deposits  of  fat  in  whales,  their  blubber, 
at  once  affords  a  protection  through  its  imperfect  conductibility,  and  is 
also  a  store  of  combustible  material  for  the  purpose  of  respiration. 

The  chief  cooling  agencies  in  animals  are,  1st.  Radiation ;  2d.  Loss 
General  cool-  °f  neat  by  warming  the  expired  air ;  3d.  Loss  by  contact  of 
ing  agencies,  the  cold  external  air ;  4th.  Evaporation.  The  circulation  of 
the  blood  tends  to  establish  an  interior  equalization,  so  that  local  varia- 
tions are  soon  obliterated ;  for,  through  whatever  part  the  blood  may  flow, 
it  attains  the  temperature  thereof,  and,  passing  in  succession  from  part  to 
part,  equalizes  the  heat  of  all. 

It  would  be  useless  to  offer  any  proof  that  a  living  being,  like  an  in- 


COOLING  AGENCIES.  '    185 

organic  mass,  loses  or  gains  heat,  as  the  case  may  be,  by  radi- 

~.  3   .  ,_         •  11       Of  radiation, 

ation.     bince,  however,  in  man,  the  temperature  is   usually 

higher  than  that  of  the  surrounding  medium,  the  result  of  this  action  is 
that  cooling  takes  place.  With  regard  to  loss  of  heat  by  warming  the 
expired  air,  it  may  be  observed  that,  whatever  the  temperature  of  the  ex- 
ternal air  may  be,  it  is  raised  to  that  of  the  lungs  after  it  has  been  brought 
into  the  respiratory  passages.  This  constitutes,  therefore,  a  cooling 
agency  of  variable  power,  for  the  loss  will  be  greater  as  the  external  heat 
is  lower :  if  the  atmospheric  temperature  rose  to  98°,  loss  in  this  manner 
would  cease.  Becalling  what  has  been  said  respecting  the  mode  in  which 
air  is  introduced,  it  is  plain  that  this  loss  will  chiefly  fall  Heat  given  to 
upon  the  nasal  passages,  the  trachea,  and  larger  ramifications  the  expired  air. 
of  the  bronchial  tubes ;  for,  by  the  time  the  volume  inspired  has  made  its 
way  beyond  that  limit,  its  temperature  must  be  nearly  that  of  the  body. 
The  contact  of  the  cold  surrounding  air,  and  more  particular-  contact  of  the 
ly  of  currents  which  may  be  occurring  in  it,  act  chiefly  upon  surrounding 
the  skin,  and  it  is  in  preventing  this  loss  that  clothing  be- 
comes so  efficient.  The  difference  we  so  frequently  notice  between  the 
indications  of  the  thermometer  and  our  own  sensations  are,  for  the  most 
part,  dependent  on  these  currents.  A  temperature  of  50°  below  zero  can 
be  sustained  without  much  inconvenience  if  the  air  is  perfectly  calm, 
but  not  so  if  there  is  any  wind.  Of  all  the  cooling  agencies,  evaporation 
is,  however,  by  far  the  most  energetic.  From  the  skin  and  Coolino.  b 
the  air  cavities,  large  quantities  of  the  vapor  of  water  are  ex-  evaporation  of 
haled.  As  the  external  heat  rises,  the  sudoriparous  tubes  act*  water< 
with  increased  energy,  and  pour  out  their  excretion  as  drops  of  sweat 
faster  than  it  can  be  removed.  Their  length  has  been  estimated  at  28 
miles.  Since,  at  the  temperature  of  the  body,  the  heat  of  elasticity  of  the 
vapor  of  water  is  1114°,  this  continued  vaporization  from  the  skin  and 
lungs  is  one  of  the  most  powerful  sources  of  refrigeration. 

It  may  be  well  to  direct  a  closer  attention  to  the  special  action  of  the 
air  passages  and  skin  as  concerned  in  these  cooling  process-  Variabilit  in 
es.  The  diurnal  loss  of  water,  by  both  organs  conjointly,  is  the  action  of 
usually  estimated  at  3£  Ibs.,  of  which  the  pulmonary  exha-  theskin- 
lation  constitutes  about  one  third,  and  the  cutaneous  about  two  thirds. 
The  skin  acts  in  a  variable  manner,  losing  more  or  less  water  as  the  ex- 
ternal air  is  dryer  or  more  damp.  The  removal  of  water  therefore  be- 
comes a  complex  operation,  in  which  three  different  organs  are  concerned 
— the  skin,  the  lungs,  and  the  kidneys.  Of  these,  the  skin  acts  meteoro- 
logically and  variably,  as  has  been  just  remarked,  and  the  respiratory  or- 
gans for  the  most  part  uniformly.  But  since  it  is  requisite,  in  the  nor- 
mal operations  of  the  system,  that  the  diurnal  average  of  water  should  be 
removed,  the  variable  action  of  the  skin  throws  a  variable  action  upon 


186    '  BALANCE   BETWEEN    HEATING   AND   COOLING. 

v<     .  the  kidneys,  for  the  excess  that  the  skin  can  not  evaporate 

tionofthekid-  must  be  strained  off  Iby  these  organs.     In  this  regard  the 

kidneys  act,  therefore,  vicariously  for  the  skin ;  and  in  hot 
weather,  when  the  cutaneous  losses  are  great,  but  little  urine  is  discharged ; 
but  in  cold  weather,  when  the  cutaneous  loss  is  diminished,  the  quantity 
of  the  urine  is  increased. 

I  think,  however,  that  as  regards  the  respiratory  organs,  a  distinction 

should  be  made  in  their  mode  of  action.     In  reality,  they 

Evaporation  in  •  J '          •> 

the  air  pas-  operate  in  a  double  way.  1st.  They  act,  so  far  as  the  nasal 
passages,  the  trachea,  and  larger  ramifications  of  the  bron- 
chial tubes  are  concerned,  meteorologically,  and  therefore  variably,  for 
the  introduced  air  possesses  the  existing  atmospheric  temperature ;  is  at 
one  time  warm,  and  at  another  cold  ;  yet,  since  it  always  leaves  these 
passages  at  94°,  it  removes  from  their  surfaces  sometimes  less  and  some- 
times more  heat ;  but  it  is  not  so  with  the  action  going  on  in  the  air- 
cells,  the  temperature  of  which,  and  of  the  air  they  contain,  is  always 
uniform  ;  and  as  water  vaporizes  into  them,  it  must  always  do  it  at  a  uni- 
form rate,  and  remove  as  its  caloric  of  elasticity  a  uniform  amount  of 
heat.  I  therefore  decompose  the  loss  of  heat  by  the  respiratory  organs 
into  two  portions :  one,  which  is  constant,  and  taking  place  in  the  cells  ; 
the  other,  variable,  occurring  in  the  large  air-ways,  and,  being  meteoro- 
logical, coincides  in  this  respect  with  the  cutaneous  loss.  In  consider- 
ing the  diseases  of  the  respiratory  organs,  it  is  well  to  keep  this  distinc- 
tion in  mind. 

The  establishment  of  the  equilibrium  of  temperature  in  an  animal  is 
Balance  be-  effected*  by  the  mutual  operation  of  the  heating  and  cooling 
ingandkooMng  arrangements.  More  or  less  heat,  as  the  system  requires, 
arrangements,  may  be  furnished  by  promoting  or  retarding  the  oxidation 
of  respiratory  material ;  and  since  a  living  being,  like  an  inorganic  mass, 
is  subject  to  every  external  influence,  its  temperature  tending  to  rise  or 
fall  as  diurnal,  or  annual,  or  seasonal  changes  may  be,  these,  as  well  as 
Elimination  of  its  own  interior  variations,  are  held  in  check  by  the  cooling 
local  variations  or  warming  powers  it  can  exert.  Local  differences  within 
tion  of  the  itself  are  eliminated  in  an  indirect,  but  still  very  effectual 
blood.  manner,  by  the  circulation  of  the  blood ;  and,  considering 

the  range  of  variation  to  which  it  is  exposed,  and  the  frequency  of  the 
changes,  the  required  equilibrium  is  admirably  secured. 

I  have  reserved  for  a  more  special  and  prominent  consideration  the  in- 
Controi  of  the  fluence  which  the  nervous  system  exerts  over  animal  heat, 
nervous  sys-  since  it  is  upon  this  that  many  have  been  disposed  to  deny 
the  great  truth  that  the  heat  of  the  body  arises  from  oxida- 
tion. They  say  that  it  is  produced  by  the  nerves.  Even  a  mental  emo- 
tion gives  rise  to  disturbance  of  temperature,  and  the  face  may  be  cover- 


INFLUENCE   OF  THE   NEEVOUS   SYSTEM.  187 

ed  with  blushes.  Moreover,  as  experiments  have  proved,  on  cutting  a 
nerve  the  temperature  of  the  parts  it  supplies  declines ;  on  injuring  the 
great  nerve  centres  the  temperature  of  the  whole  system  lowers,  even 
though  artificial  respiration  may  "be  kept  up.  In  cases  of  paralysis,  the 
temperature  of  the  disabled  part  may  be  very  much  lower  than  that  of 
the  sound.  A  paralyzed  arm  has  shown  a  surface  heat  of  70°  only, 
while  the  sound  one  has  been  at  92°.  It  is  also  said  of  decapitated  ani- 
mals that  they  cool  quicker  when  artificial  respiration  is  kept  up  than 
when  they  are  let  alone. 

All  this  may  be  very  true,  yet  it  is  very  far  from  proving  that  the 
nerves  are  the  generators  of  animal  heat.  The  engineer  of  a  locomotive 
can  regulate  the  speed  of  his  train  and  control  the  production  of  steam  by 
throwing  more  or  less  fuel  on  the  fire,  or  by  supplying  it  with  more  or  less 
air ;  but  does  any  one  impute  the  production  of  the  heat  to  him  ?  If 
an  accident  should  throw  him  off,  thereby  establishing  a  sort  of  analogy 
between  his  machine  and  the  decapitated  animals  we  have  referred  to,  the 
stoppage  that  would  soon  ensue,  and  the  dying  out  of  the  fire,  would  by 
no  means  prove  that  he  made  the  heat ! 

And  so  with  the  nervous  system,  its  function  is  not  a  generative,  but 
a  controlling  one.  It  determines  in  what  way  the  combustive  or  oxidiz- 
ing actions  shall  go  on,  but  that  is  a  totally  different  affair  from  forming 
the  heat. 

Before  specifying  more  particularly  the  views  I  entertain  on  this  sub- 
ject, I  will  remark,  that  the  most  superficial  consideration  satisfies  us 
that  oxidation  in  the  system  goes  on  in  a  regulated  way.  There  is  not 
an  indiscriminate  attack  made  by  the  arterial  blood  on  whatever  is  next 
before  it,  but  those  particles  only  are  removed  which  the  needs  of  the 
system  require.  This  therefore  implies  some  overriding  or  superintend- 
ing agency,  which  can  save  one  atom  from  destruction  and  surrender  an- 
other. The  portion  assaulted  may,  to  all  appearances,  be  identical  in 
physical  aspect  and  chemical  constitution  to  an  adjacent  one  that  is  pass- 
ed by.  There  seems  to  be  an  arrest  or  suspension  of  affinity  in  one  case, 
and  its  ready  satisfaction  in  the  other. 

There  are  some  well-known  facts  in  natural  philosophy  which  throw 
a  flood  of  light  on  this  obscurity.  If  a  piece  of  pure  zinc  physical  anal- 
be  placed  in  a  glass  of  acidulated  water  beside  a  piece  of  °sies  to  this 

,  111  ^  i  control  of  the 

copper,  so  long  as  the  metals  are  kept  apart  no  action  what-  nervous  sys- 
ever  ensues ;  but  if  a  conducting  thread  is  laid  from  one  to  tem* 
the  other,  the  zinc  instantly  begins  to  oxidize,  clouds  of  hydrogen  gas 
bubbles  rise  from  the  copper,  and  the  thread  becomes  at  once  red-hot  and 
magnetic.     On  lifting  the  communicating  thread  all  these  actions  cease ; 
on  restoring  it  they  instantly  recur.     We  think  we  explain  them  by  say- 
ing that  they  are  all  due  to  the  decomposition  of  water  by  the  zinc.     But 


188  ALLOTEOPISM   OF   OEGANIC   BODIES. 

why  was  the  zinc  passive  when  alone,  and  why  did  it  assume  this  activ- 
ity when  merely  touched  by  another  metal  ?  Does  not  all  this  serve  to 
show  that  substances  may  be,  as  it  were,  in  a  quiescent  state,  and  on  the 
application  of  what  may  perhaps  seem  the  most  insignificant  cause,  may 
suddenly  assume  activity,  and  forthwith  satisfy  their  chemical  affinities  ? 
There  is  nothing  in  the  graduated  oxidations  going  on  in  the  system 
more  obscure  or  more  unaccountable  than  the  phenomena  of  a  simple 
Voltaic  circle.  Their  effects  are  almost  parallel. 

All  elementary  substances  appear  to  have  the  quality  of  assuming  active 
Allotropism  of  and  passive  conditions.  Carbon,  moreover,  presents  many 
bodies.  intermediate  forms.  As  diamond  it  is  extremely  incombus- 

tible, and  is  set  on  fire  with  difficulty  even  in  oxygen  gas  ;  as  lampblack 
it  will  kindle  spontaneously.  With  these  differences  in  its  relations  with 
oxygen,  it  also  exhibits  great  variations  in  its  optical,  calorific,  mechan- 
ical, and  other  properties.  These  transitions  of  state  may  be  induced  by 
various  causes,  especially  by  the  agency  of  what  are  called  the  impon- 
derable principles,  as  by  rise  of  temperature,  and  exposure  to  the  sun- 
light. Thus,  in  the  case  of  chlorine,  I  have  shown  that,  though  it  re- 
fuses to  combine  with  hydrogen  so  long  as  it  is  in  the  dark,  an  exposure 
to  indigo-colored  light  will  cause  it  to  unite  with  explosive  energy  with 
that  substance ;  and  these  peculiarities  are  retained  by  bodies  when 
they  go  into  union  with  each  other.  Thus  there  are  two  forms  of  phos- 
phorus; the  one  active  and  shining  in  the  dark,  and  therefore  readily  oxi- 
dizable ;  the  other  passive,  not  shining  in  the  dark,  and  with  therefore  a 
less  affinity  for  oxygen ;  and  these  severally  give  rise  to  two  varieties 
of  phosphureted  hydrogen,  which,  though  having  the  same  composition, 
yet  differ  in  thi's  respect,  that  the  one  containing  the  active  form  of  phos- 
phorus is  spontaneously  combustible  in  the  air,  but  the  other,  which  con- 
tains the  passive  form,  is  not  spontaneously  combustible.  Phosphorus 
is  thrown  from  the  active  to  the  inactive  state  by  mere  exposure  to  the 
more  refrangible  rays  of  the  sun. 

The  properties  here  spoken  of  have  been  designated  by  Berzelius  as 
Allotropism  of  ^ie  a^otropism  of  bodies.  I  have  endeavored  to  prove  that 
organized  bod-  allotropism  is  the  true  cause  of  many  of  the  obscure  facts 
which  we  meet  with  in  the  animal  mechanism ;  for  it  is  very 
clear  that  something  so  modifies  the  relations  of  the  tissues  to  oxygen 
that  they  are  not  indiscriminately  destroyed  by  it,  but  these  parts  yield 
in  a  measured  or  regulated  way ;  and  since,  in  inorganic  substances,  the 
influence  of  the  imponderables  can  compel  the  assumption  of  an  active  or 
passive  state,  there  is  nothing  contradictory  in  imputing  to  the  nervous 
system  a  similar  power. 

In  this  manner  we  may  therefore  conclude  that,  so  far  as  tissue  de- 
struction is  concerned,  the  nervous  system  possesses  a  governing  or  con- 


OF  SECRETION.  189 

trolling  power ;  that  by  keeping  parts  in  states  answering  to  the  passive 
and  active  conditions  of  inorganic  chemistry,  it  can  suspend  the  action  of 
the  respired  oxygen  or  permit  it  to  take  effect.  This  controlling  power 
is,  however,  altogether  distinct  from  a  generative  one,  and  all  the  heat  dis- 
engaged is  due  to  oxidation.  It  is  also  possible  that  not  only  are  these 
states  of  activity  or  passivity  impressed  on  the  tissues  by  the  agency  of 
the  nerves,  but  also  upon  the  respired  oxygen  itself,  since  that  gas  is  no 
exception  to  the  rule ;  it  also  exhibits  allotropism.  Its  passive  state  is 
Priestley's  oxygen,  its  active  is  Ozone.  In  its  transit  from  the  air-cells 
into  the  blood  it  may  experience  such  a  change,  and  have  at  once  com- 
municated to  it  a  high  degree  of  activity. 


- 
CHAPTER  XL  ; 

OF  SECRETION. 

SEROUS,  MUCOUS,  AND   HEPATIC    SECRETIONS. 

of  Secretion. — Type  of  secreting  Mechanism. — Filtration  and  Cell  Action. — Of  Serous 
Membranes  and  their  Secretions. — Of  Mucous  Membranes  and  their  Secretions. — Of  Hepatic  Se- 
cretions.— The  Liver:  its  Development  and  Structure. — Source,  Quantity,  Composition,  Uses, 
and  Flow  of  the  Bile. — Existence  of  biliary  Ingredients  in  the  Blood. — Production  of  Sugar  and 
Fat  in  the  Liver. —  Changes  of  the  Blood-cells  in  it. — General  Summary  of  the  four-fold  Action 
of  the  Liver:  it  produces  Sugar  and  Fat,  eliminates  Bile,  is  the  Seat  of  the  final  Destruction 
of  old  Blood-cells,  and  of  the  Completion  of  new  Ones. — Of  the  ductless  Glands. — The  Spleen: 
its  Functions. 

Two  classes  of  substances  occur  in  the  blood — the  products  of  decay 
and  the  elements  of  nutrition.  The  equilibrium  of  the  system  requires 
that  the  former  should  be  removed  and  the  latter  appropriated. 

The  primary  object  of  the  function  of  secretion  is  this  dismissal  and 
appropriation,  and  therefore,  through  the  latter  duty,  secre-  object  of  secre- 
tion becomes  connected  with  nutrition.  tion- 

The  elementary  type  of  a  gland  or  organ  of  secretion  consists  ot  a  sac, 
on  the  interior  of  the  wall  of  which  a  network  of  arterial  ramifi-  Type  of  a 
cations  is  spread ;  this  delivers  its  blood  into  a  similar  network  eland- 
of  veins.  The  matter  which  the  gland  is  destined  to  separate  oozes 
from  the  arterial  capillaries  into  the  interior  of  the  sac,  and  is  delivered 
through  the  neck  or  mouth  thereof,  which  may  be  spoken  of  as  the  duct. 
It  will  be  presently  shown  that  the  material  which  thus  finds  its  way 
into  the  interior  of  the  sac  is  not  fabricated  by  that  organism,  but  is 
brought  to  it  pre-existing  in  the  affluent  current  of  arterial  blood.  As 
our  knowledge  of  the  functions  of  glandular  structures  becomes  more 


190  VICARIOUS   SECRETION. 

precise,  the  less  and  less  does  it  appear  probable  that  the  secreted  matter 
is  in  any  way  engendered  by  the  gland  itself. 

Since,  with  the  exception  of  the  lungs,  which  excrete  carbonic  acid  and 

.    vapor  of  water,  all  the  great  glands  remove  the  material  they 

glandular   are  concerned  with  in  a  state  of  liquid  solution,  it  follows  of 

necessity  that  the  blood  of  the  artery  supplying  the  gland,  and 

that  removed  by  the  vein  from  the  gland,  differ  in  two  respects  :   1st.  In 

the  peculiar  material  constituting  the  solid  secreted ;   and,  2d.  In  the 

quantity  of  water.     From  the  latter  cause  it  must  follow  that  the  venous 

blood  will  have  a  greater  spissitude  than  the  arterial. 

This  elementary  or  typical  form  of  a  gland  is  but  very  little  departed 
from  in  those  cases  in  which  the  sac  is  elongated  into  a  tube ;  and  even 
where  this  has  been  extended  to  an  exaggerated  degree,  the  essential 
principle  of  action  still  remains  the  same. 

From  the  constancy  of  aspect  which  glands  present,  we  might  be  led 
Influence  of  at  first  to  suppose  that  their  peculiarities  of  construction  de- 
by'viSous  a<>  termme  their  physiological  action,  that  the  liver  secretes  bile, 
tion.  and  the  kidney  urine,  because  they  have  the  special  organ- 

ization which  is  needful  for  such  purposes.  Such  a  supposition,  how- 
ever, has  to  be  received  with  much  limitation,  as  is  proved  by  number- 
less cases  of  vicarious  action.  Thus,  in  morbid  difficulties  of  the  liver, 
the  skin  will  discharge  its  duty  for  it  in  the  elimination  of  the  bile ;  and 
in  derangements  of  the  kidneys,  the  mammary  gland,  the  mucous  mem- 
brane of  the  nose,  or  even  the  stomach,  will  discharge  urine.  Construct- 
ive arrangements  have  therefore  for  their  object  the  facilitating  of  a  secre- 
tion, but  they  do  not  produce  it.  Thus  the  liver  is  far  better  fitted  for 
separating  bile,  or  the  kidney  urine,  than  is  the  skin  for  each  of  these  re- 
spectively ;  but  if  they  become  incapacitated,  the  skin  is  able  to  act  vica- 
riously for  them. 

Though  such  vicarious  action  has  been  denied  by  some  physiologists 
Connection  of  as  being  totally  incompatible  with  anatomical  indications,  a 
tioiuinTdevel-  more  profound  conception  of  the  law  of  development  of  these 
opment.  structures  may  satisfy  us  that  it  is  in  reality  a  physiological 

probability,  apart  from  the  evidence  we  have  often  derived  from  interest- 
ing instances  of  its  actual  occurrence.  It  will  be  seen,  when  we  treat  of 
the  primitive  appearance  of  the  different  secreting  organs,  that  they  are, 
in  reality,  all  evolved,  as  it  were,  from  a  common  surface  or  membrane ; 
that  this  primitive  surface  discharged,  though  perhaps  in  a  confused  way, 
all  their  functions  collectively ;  and  that  in  development  the  ruling  idea 
seems  to  be  the  separating  out,  or  localizing  upon  a  determinate  spot  or 
region,  structures  which  should  have  the  duty,  in  a  special  manner  at- 
tached to  them,  of  removing  this  or  that  particular  substance,  a  central- 
ization or  concentration  of  action  thus  occurring.  There  is  therefore 


FILTEATION  AND   CELL  ACTION.  191 

nothing  extraordinary  that,  under  the  pressure  of  circumstances,  one  of 
the  special  structures  should,  in  an  imperfect  way,  resume  the  action 
which  it  once  enjoyed,  while  it  was  yet  a  part  of  the  common  structure ; 
but,  however  this  may  be,  the  cases  of  vicarious  action  are  too  numer- 
ous and  too  well  authenticated  to  admit  of  any  doubt. 

Though  these  vicarious  actions  may  be  in  a  certain  degree  imperfect, 
they  are  of  the  highest  importance  physiologically,  since  they  indicate  the 
true  nature  of  the  function,  and  place  the  influence  of  structure  in  its 
proper  attitude. 

The  separation  of  material  from  the  blood  may,  however,  for  the  pres- 
ent, be  considered  as  conducted  in  two  different  ways ;  1st,  by  filtration  ; 
2d,  by  cell  action. 

Secretion  by  filtration  is,  of  course,  a  purely  physical  act.  The  trans- 
udation  of  water  charged  with  saline  substances,  or  with  more  Separation  of 
or  less  of  albumen,  seems  to  imply  nothing  but  the  escape  of  ^f^oo^by 
pre-existing  bodies  through  pervious  or  porous  membranes,  filtration. 
Such  a  result  is  presented  in  the  case  of  the  lachrymal  gland,  the  duty 
of  which  is  to  accomplish  a  definite  mechanical  operation  for  the  eye  in 
keeping  the  cornea  clear  and  transparent.  This  mechanical  function  is 
again  observed  in  the  case  of  the  serous  membranes,  and  particularly  the 
synovial  ones,  in  which  the  relief  of  friction  of  movable  parts  seems  to  be 
the  object  aimed  at. 

As  long  as  the  material  secreted  clearly  pre-exists  in  the  blood,  it  is 
needless  to  refer  secretion  to  any  other  principle  than  the  simple  one  of 
transudation  or  filtration.  It  would  be  unphilosophical  to  suppose  that 
the  lachrymal  gland  exercises  any  property  for  the  formation  or  produc- 
tion of  water  when  by  mere  transudation  copious  supplies  of  that  sub- 
stance can  be  obtained  from  the  blood. 

But  secretion  is,  moreover,  perhaps  connected  with  cell  life.  On  the 
upper  part  of  the  intestine  of  the  young  chick,  a  few  cells  secretion  by 
make  their  appearance  about  the  fourth  day  of  incubation,  cell  action. 
They  are  eventually  recognized  as  bile-containing  cells  from  the  color  of 
their  contents.  As  the  process  goes  on,  the  spot  they  occupy  buds  off, 
as  it  were,  so  as  to  produce  a  blind  pouch.  This  offshoot,  with  its  ex- 
terior cells,  is  eventually,  when  perfect  development  is  reached,  the  liver. 
Secreting  organs  of  this  glandular  class,  and  also  membranes,  possess  a 
general  analogy:  they  consist  of  a  structureless  basement  membrane,  with 
cells  upon  its  surface,  and  a  supply  of  blood-vessels.  The  cells  are  not 
persistent,  but  lead  a  very  transitory  life,  apparently  elaborating  the  ma- 
terial with  which  they  are  charged,  and  then  undergoing  rupture  or  deli- 
quescence. 

Our  conclusion  respecting  the  mode  of  action  of  secreting  cells  turns 
altogether  upon  the  evidence  of  the  power  they  possess  of  preparing  ma- 


192  FILTEATION   AND   CELL   ACTION. 

terial  which  did  not  pre-exist  in  the  blood.  Thus,  if  it  should  be. shown 
that,  under  normal  circumstances,  the  elements  of  bile  are  not  found  in  the 
blood,  the  inference  might  be  drawn  that  the  hepatic  cells  display  a  com- 
bining, or,  as  it  were,  a  preparing  power ;  and  so  likewise  in  the  case  of 
other  secreting  cells ;  but  the  weight  to  be  attached  to  such  evidence  is 
greatly  affected  by  the  consideration  that  the  action  of  each  gland  or  se- 
Difficuityofde-  creting  apparatus  masks  what  is  really  going  on  in  the  sys- 

ofCsec?etio"inS  tem*  ^  *s  P088^6  tnat  we  ma7  l°e  scarcely  able  to  discov- 
the  blood.  er  the  traces  of  substances  in  the  blood,  and  yet  a  tendency 
may  exist  for  their  accumulation  to  a  great  extent.  Thus  there  can  be 
no  doubt  that  urea  would  abound  through  the  disintegration  of  the  mus- 
cular structures,  and  the  use  of  nitrogenized  food,  if  it  were  not  for  the 
action  of  the  kidneys.  It  is  the  very  perfection  of  that  action  which  so 
diminishes  the  amount  in  the  circulation  as  to  prevent  us,  except  with 
difficulty,  from  detecting  the  presence  of  the  ingredient. 

Nor  is  this  all,  for  it  ought  to  be  remembered  that  many  of  the  prod- 
ucts of  secretion  are  substances  undergoing  retrograde  metamorphoses, 
and  have  therefore,  as  it  were,  in  themselves,  an  interior  principle  of 
change.  It  is  conceivable  that  things  which  did  not  pre-exist  in  the 
blood  may  yet  occur  in  the  secretions,  coming  tnere,  not  through  the 
agency  of  cell-life,  but  because  of  the  downward  course  toward  an  inor- 
ganic condition  through  which  the  secretion  is  spontaneously  passing. 

Of  the  more  prominent  substances  in  the  chief  secretions,  many  indis- 
putably pre-exist  in  the  blood.  Urea,  cholesterine,  casein,  are  examples. 
Wherever  this  occurs,  the  removal  is  unquestionably  due  to  mere  filtra- 
tion. Why  should  it  be  supposed  that  the  cells  of  the  kidneys  have  any 
duty  of  combining  material  presented  to  them  into  urea,  or  those  (if  the 
liver  into  cholesterine,  or  those  of  the  mammary  glands  into  casein  ?  As 
our  methods  of  examining  the  blood  become  more  perfect,  this  formative 
or  grouping  action,  once  so  largely  imputed  to  the  secreting  cells,  be- 
comes more  and  more  restricted. 

The  cases  in  which  the  influence  of  cells  is  indisputable  are  those  which 
Conditions  of  °^er  to  us  com^mations  of  progressive  metamorphosis.  Of 
filtration  and  these,  the  most  striking  instance  is  the  preparation  of  the  sper- 
of  cell  action.  matic  ^^  Perhaps  we  should  not  be  very  far  from  the  truth 
if  we  considered  all  those  secretions  in  which  the  materials  are  in  a  state  of 
retrograde  metamorphosis,  or  in  a  descending  career,  as  arising  by  mere 
filtration,  and  those  which  are  ascending  to  a  higher  grade  as  due  to  cell 
agency;  between  the  two  there  being  an  intermediate  class,  the  phase  of 
which  is  stationary,  and  in  which  cells  may  or  may  not  be  necessarily 
involved,  as,  for  instance,  the  transmutation  of  one  fat  into  another,  or 
the  preparation  of  sugar  from  albumenoid  bodies. 

The  apparatus  for  secretion  is  generally  conveniently  treated  of  under 


SECRETIONS   OF  SEROUS  MEMBRANES.  193 

two  heads  :  1st.  Membranes,  such  as  the  serous  and  mucous ;  2d.  Glands, 
as  the  liver,  kidney.  This  division  is,  however,  not  founded  either  on 
structural  or  functional  differences,  and  is  to  be  preserved  merely  for  the 
sake  of  convenience. 

A  secreting  membrane  consists  essentially  of  a  tunic  of  connective  tis- 
sue, affording  a  nidus  for  vessels  and  nerves.  Upon  this,  in  the  opinion 
of  many  anatomists,  a  thin  basement  membrane  is  laid,  the  existence  of 
which  is  denied  by  others.  Upon  the  surface  of  the  basement  membrane 
there  is  a  layer  of  cells,  the  form  and  arrangement  of  which  differ  in 
different  regions.  In  some  places  the  cells  are  flat,  in  others  cylindroid. 
Their  duration  is  temporary,  one  brood  succeeding  another  from  germs  on 
the  basement  membrane.  The  superficial,  and,  therefore,  the  older  cells, 
desquamate  or  deliquesce,  and  are  replaced  by  others  from  beneath.  It 
is  usually  said  that  the  serous  membranes,  with  the  exception  Of  serous  mem 
of  the  peritoneum,  are  all  closed  sacs,  the  peritoneum  being  branes  and 
perforated  where  the  fimbriated  extremities  of  the  Fallopian  their  secretion' 
tubes  open  into  the  abdominal  cavity  in  the  mammalia,  and  in  fishes 
through  the  lateral  anal  openings.  The  generality  of  this  view  is  now 
called  in  question,  both  as  regards  the  sy  no  vial  sacs  and  bursse  mucosas, 
which  all  belong  to  this  group.  Thus  Kolliker  regards  the  synovial 
structures  as  tubes  open  at  both  ends,  and  attached  by  their  edges  round 
the  articular  surfaces  of  the  bones. 

However  this  may  be,  even  the  peritoneum  is  practically  a  shut  sac. 
Accumulations  of  water  within  it  do  not  escape  through  the  apertures  of 
the  Fallopian  tubes,  nor  can  air  be  injected  the  opposite  way. 

The  fluid  exuding  from  the  serous  surfaces  is  a  dilute  albuminous  so- 
lution, more  dilute  as  it  is  presented  in  the  ventricles  of  the  _ 

n  T  .       ,  •  i          •  •  Serous  fluids. 

brain,  and  more  concentrated  in  the  synovia!  cavities,  its  con- 
sistency in  the  latter  case  being  such  that  it  may  sometimes  be  drawn 
out  in  tenacious  threads.  The  mechanical  qualities  of  these  various  ex- 
udations permit  a  certain  freedom  of  motion  in  the  parts  to  which  they 
are  applied.  Thus  the  secretion  of  the  peritoneum  facilitates  the  move- 
ments of  the  abdominal  viscera ;  those  of  the  pericardium  and  pleura,  of 
the  heart  and  lungs ;  those  of  the  synovial  membranes  and  bursa3  mu- 
cos03,  of  the  joints  and  tendons. 

The  nature  of  serous  secretions  may  be  illustrated  by  the  cases  of 
fluids  collected  from  the  abdominal  and  thoracic  cavities,  &c.  They 
are  usually  of  a  faint  yellowish  color,  clear  or  turbid,  reaction  alkaline, 
and  sometimes  containing  so  much  albumen  as  to  coagulate  readily  on 
heating. 

N 


194  CONSTITUTION    OF   SEROUS   FLUIDS. 

TABLE  I. 
fluid  of  Asdtes.     (From  Marchand.') 

Water 952.30 

Albumen 23.80 

Urea 4.20 

Chloride  of  sodium 8.10    ^ 

Carbonate  of  soda 2.10 

Phosphate  and  traces  of  sulphate  of  soda 0.60 

A  viscid  substance 8.90 

1000.00 

TABLE  II. 
Asdtes  with  Suppuration  of  both  Kidneys.     (From  Simon?) 

Water 978.00 

Fat  containing  cholesterine 1.00 

Albumen 8.40 

Alcohol  extract 0.30 

Spirit  extract 1.70 

Carbonate  of  soda  and  phosphate  of  lime 1 .20 

Chloride  of  sodium  and  lactate  of  soda 6. 80 

Urea 1.20 

Loss 1.40 

1000.00 

TABLE  in. 
Pleural  Effusion.     (From  Simon.') 

Water 934.72 

Fibrin 1.02 

Fat 1.05 

Alcohol  extract,  with  salts 1.35 

Spirit  extract,  with  salts. 10.64 

Albuminate  of  soda 17.86 

Albumen 31.00 

Fixed  salts :..       9.50 

Gain  in  analysis 7.14 

1000.00 

To  the  above  may  be  added  the  following  interesting  instances  of  fluid 
of  hydrocele,  in  which  attention  should  be  particularly  directed  to  the  oc- 
currence of  cholesterine  and  other  bile  constituents.  In  the  case  pre- 
sented in  Table  IV.,  the  fluid  was  observed  to  sparkle  when  shaken,  in 
consequence  of  the  numberless  crystals  of  cholesterine : 

TABLE  IV. 
Fluid  of  Hydrocele.     (From  Simon.*) 

Water 860.00 

Cholesterine,  with  a  little  margarine  and  oleic  acid      8.40 

Albumen 48.30 

Albuminate  of  soda  and  extractive  matter 6.88 

Extractive  matter  soluble  in  alcohol 2.30 

Chlorides  of  sodium  and  calcium,  a  little  sul-  >      <-9  -<> 

phate  and  traces  of  phosphate  of  lime £ 

Phosphate  of  lime  and  traces  of  peroxide  of  iron...         .70 

Loss 0.90 

1000.00 


FEE-EXISTENCE   OF   SECRETED   PRODUCTS.  195 

TABLE  V. 
Fluid  of  Hydrocele.     (From  Heller.) 

Water 919.20 

Albumen 58.00 

Free  fat 1.60 

Soda  soap,  biliphaein,  haemato-globulm,  dissolved  ) 

hsematin,  and  extractive \ 

Fixed  salts 7.30 

1000.00 

TABLE  VI. 
Fluid  of  Hydrocele.     (From  Heller.) 

Water 906.36 

Albumen 60.00 

Fat  containing  cholesterine 0.23 

Extractive  matters,  biliphaein,  soda  soap 24.04 

Fixed  salts,  chiefly  chloride  of  sodium 9.37 

1000.00 

TABLE  VII. 
Synovial  Fluid.    (From  Frerichs.) 

Water 948.00 

Mucus  and  epithelium 5.00 

Fat 0.70 

Albumen  and  extractive 35.00 

Salts 9.00 

Loss 2.30 


1000.00 


I  have  introduced  these  tables  not  only  for  the  purpose  of  exhibiting 
the  nature  of  the  fluid  yielded  by  membranes  of  the  serous  Products  of  ee- 
group,  but  also  for  the  sake  of  the  important  evidence  they  j^°n.  P ^x~ 
offer  as  regards  the  function  of  secretion  itself.  In  the  jn-  blood, 
fancy  of  physiology  it  was  universally  believed  that  the  special  function 
of  each  gland  arose  from  its  peculiarity  of  construction  ;  that  thus,  by^he 
liver,  out  of  blood  in  which  they  did  not  pre-exist,  cholesterine  and  its 
allied  bile  compounds  were  made ;  that  thus,  by  the  kidney,  urea  was 
formed.  Even  in  more  recent  times  a  modification  of  this  doctrine  has 
prevailed,  and  to  the  cells  of  which  glands  are  so  largely  composed,  the 
duty  has  been  attributed  of  forming  special  products.  In  this  way,  we 
still  constantly  speak  of  the  bile-secreting  cells  of  the  liver;  but  the  pre- 
ceding tables  indisputably  show  that  these  very  compounds,  cholester- 
ine, biliphaein,  urea,  etc.,  may  make  their  appearance  in  distant  places, 
oozing  from  surfaces  wholly  devoid  of  the  supposed  special  mechanism. 
In  cases  in  which  there  occurs  structural  degeneration  of  the  kidneys, 
for  instance,  urea  at  once  makes  its  appearance  in  unaccustomed  places, 
as  though,  when  the  readiest  avenues  through  which  it  might  have  es- 
caped have  failed,  it  bursts  forth  or  oozes  out  at  the  weakest  point. 
With  such  results,  the  idea  of  leakage  or  straining  seems  to  be  insepara- 


196  OF   ELECTIVE    FILTEATION. 

bly  connected ;  and,  moreover,  an  enlarged  view  of  the  operation  of  cell 
life  seems  to  indicate  that  the  general  action  of  those  organisms  is  to 
produce  a  formative  result,  the  grouping  of  amorphous  into  organized 
material,  and  the  elaboration  of  that  material  into  more  complicated  and 
higher  forms.  But  many  of  the  most  important  constituents  of  the  va- 
rious secretions  are  indisputably  things  which  are  on  the  downward  ca- 
reer, fast  passing  to  the  inorganic  state.  Many  of  them,  as  presented  in 
the  bile  or  in  the  urine,  run  through  a  series  of  spontaneous  changes, 
which  end  in  the  appearance  of  truly  inorganic  bodies.  For  the  fabrica- 
tion of  such  substances,  half  inorganic  themselves,  it  is  scarcely  to  be 
thought  that  cell  life  should  be  necessary ;  and  these,  with  many  other 
such  considerations,  recall  the  observation  I  made  a  few  pages  back,  that 
the  more  profoundly  we  study  the  composition  and  constitution  of  se- 
creted fluids,  and  the  more  accurately  we  understand  the  function  of  se- 
cretion itself,  the  less  are  we  disposed  to  invoke  the  agency  of  cell  life, 
and  to  rely  the  more  on  the  ordinary  mechanical  act  of  strainage. 

That  the  different  secreting  surfaces  exercise  an  elective  elimination  on 
Elective  filtra-  materials  existing  in  the  blood,  some  permitting  the  escape 
tlon*  of  one,  and  some  of  another  ingredient  more  readily,  may  be 

demonstrated  from  their  action  on  saline  substances  purposely  introduced 
into  the  blood.  Thus  the  iodide  of  potassium  was  detected  by  Bernard 
in  the  saliva,  pancreatic  juice,  and  the  tears  in  less  than  one  minute, 
but  in  the  urine  and  bile  not  until  after  an  hour.  The  ferrocyanide  of 
potassium  could  be  recognized  in  the  urine  in  seven  minutes,  but  not  at 
all.  in  the  saliva.  In  like  manner,  cane-sugar  and  grape-sugar  appear  in 
the  secretions  of  the  kidneys  and  liver,  but  not  in  those  of  the  pancreas 
and  salivary  glands.  The  lactate  of  iron,  injected  into  the  veins,  fur- 
nishes no  iron  to  the  saliva,  but  both  iodine  and  iron  can  be  recognized 
in  Jliat  secretion  after  the  administration  of  the  iodide  of  iron. 

Upon  the  whole,  we  may  therefore  conclude  that  very  many  substances 
are  strained  from  the  blood  in  which  they  naturally  occur  by  membranes 
and  glands,  which,  from  the  circumstance  that  they  are  of  various  con- 
struction and  possess  a  different  physical  nature,  are  better  adapted,  some 
for  the  removal  of  one,  and  some  for  the  removal  of  another  compound. 

Among  secreting  surfaces  the  mucous  membranes  are  usually  enumer- 
Of  mucous  ated.  Strictly  speaking,  however,  they  are  scarcely  so  much 
mfdtheir^secre-  secretmg  surfaces  as  the  seat  of  numberless  secreting  organ- 
tion.  isms.  They  line  the  interior  of  the  digestive,  respiratory, 

urinary,  and  generative  apparatuses,  and  are  characterized  by  extreme  vas- 
cularity.  In  structure  they  consist  of  several  different  layers  or  regions, 
the  undermost  being  submucous  cellular  tissue,  upon  which  is  spread  the 
proper  mucous  membrane,  containing  connective  and  elastic  tissue,  which 
affords  a  nidus  for  blood-vessels  and  nerves.  Upon  this  is  the  basement 


PROPERTIES   OF  MUCUS.  197 

membrane,  covered  with  epithelial  cells.  In  many  regions  this  compound 
structure  rises  into  elevations,  as  in  the  intestinal  villi,  or  sinks  into  de- 
pressions, as  in  the  follicles. 

The  epithelial  cells  are  of  different  kinds,  sometimes  flat,  giving  origin 
to  tesselated  or  pavement  epithelium,  and  sometimes  cylin- 

T     .,  i         n     -        i  •  -i    •  -n  ,       Epithelial  cells. 

droid,  each  cell,  in  this  case,  being  set  vertically  upon  the 
basement  membrane.  In  many  instances,  the  cylindroid  nucleated  cells 
are  furnished  upon  their  outer  extremity  with  vibrating  cilia,  constituting 
ciliated  cylindroid  epithelium.  Both  forms  of  epithelium,  the  tesselated 
and  the  cylindroid,  coexist  in  glandular  ducts.  The  origin  of  the  cells 
is  in  the  basement  membrane,  from  germs  arising  there ;  and  as  the  older 
and  therefore  superficial  cells  exuviate  or  deliquesce,  new  ones  arise  to 
take  their  places. 

After  what  has  been  said,  it  is  not  necessary  to  give  a  detailed  de- 
scription of  mucous  surfaces  farther  than  to  state  that  from  properties 
them  there  is  furnished  a  viscid,  glairy  fluid,  of  different  shades  * of  mucus, 
of  color  from  white  to  yellow,  denser  than  water,  and  insoluble  therein. 
Examined  by  the  microscope,  it  contains  granular  corpuscles  and  epithe- 
lial cells.  Its  reaction  is  alkaline,  and  its  proximate  constituent  is  a  sub- 
stance to  which  the  name  of  mucin  has  been  given.  Derived  from  dif- 
ferent sources,  as  the  nasal,  bronchial,  and  pulmonary  surfaces,  the  in- 
testinal canal,  and  the  urinary  and  gall  bladders,  it  exhibits  specific  dif- 
ferences. Its  quantity  is  often  greatly  increased  by  morbid  causes,  as, 
for  example,  in  catarrh,  its  composition  likewise  varying  at  different 
stages  of  the  same  disease.  Its  use,  for  the  most  part,  seems  to  be  the 
protection  of  the  delicate  structure  which  secretes  it.  In  some  positions, 
as  in  the  intestinal  canal,  it  likewise  probably  acts  in  the  way  of  reliev- 
ing friction  of  the  substances  passing  over  surfaces. 

Of  secreting  Glands. — The  typical  form  of  secreting  cell-gland  is  a 
single  cell,  with  its  nucleus  at  the  lower  end,  the  other  end  simple  sac-like 
having  become  open  by  deliquescence  or  dehiscence,  and  thus  cell-gland, 
constituting  a  sac.  From  the  nucleus  thus  situated  at  the  end  of  the 
cavity  broods  of  young  cells  arise.  These  become  more  perfect  as  they 
advance  toward  the  mouth  of  the  sac.  The  outer  wall,  and  especially 
the  region  of  the  nucleus,  is  furnished  copiously  with  blood-vessels. 

Of  such  structures,  variously  modified,  the  different  glands  are  com- 
posed. We  shall  now  proceed  to  the  description  of  the  more  important 
of  these,  as  the  liver,  kidneys,  mammary  gland,  &c.,  again  impressing 
the  remark  that,  though  all  these  glands  are  the  seats  of  myriads  of  cells, 
cell  life  is  for  increased  organization,  and  secretion  is  in  many  instances 
nothing  more  than  filtration  or  strainage.  We  shall  endeavor,  as  the 
occasion  arises,  to  show,  in  the  case  of  each  gland,  what  part  of  its  action 
is  due  to  cell  influence,  and  what  to  such  mechanical  permeation. 


198 


DEVELOPMENT   OF   THE   LIVER. 


OF  THE  LIVER. 

The  first  appearance  of  a  bile-secreting  organ  is  the  occurrence  of  yel- 
Rudiment  of  l°w  CQ^S  variously  scattered  upon  the  lining  membrane  of  the 
the  liver.  digestive  cavity,  as  in  the  hydra.  A  concentration  or  local- 
ization next  ensues,  such  yellow  cells  being  grouped  upon  the  wall  of  the 
intestin3  at  a  definite  spot.  A  ccecal  projection,  in  the  higher  tribes, 
seems  next  to  force  out  the  yellow  cells,  bearing  them  on  its  exterior,  as 
in  the  nudibranchiate  gasteropods  ;  and  as  these  cceca  are  prolonged 
more  and  more,  so,  in  a  more  definite  manner,  does  the  rudimentary  liver 
appear.  In  molluscs  this  partition  is  sufficiently  distinct.  The  special 
form  which  the  hepatic  apparatus  presents  in  different  tribes  varies  very 
greatly,  though  doubtless  the  principle  of  construction  and  of  action  is 
always  the  same.  Thus,  in  insects,  the  liver  con- 
sists of  long  tubes  of  delicate  membrane,  covered 
with  secreting  cells,  small  and  germ-like  near  the 
distant  end  of  the  tube,  but  more  perfect  at  the 
mouth.  These  tubes  are  in  relation  with  an  adi- 
pose mass,  which  is  probably  connected  with  the 
origin  of  the  cells.  The  different  condition  of 
these  cells,  when  compared  at  the  bottom  and  at 
the  mouth  of  the  bile-sac,  is  well  seen  in  the 
case  of  crustaceans,  as  in  Fig.  82,  one  of  the  he- 
patic coeca  of  the  cray-fish.  The  letters  at  the 
side  show  the  state  of  the  cells  in  different  posi- 
tions toward  the  mouth  of  the  follicle.  At  a  they 
contain  yellow  biliary  matter  only  ;  at  b,  oil  glob- 
ules are  appearing  in  them,  which  become  more 
distinct  at  c  /  and  toward  d  and  e  they  present 
the  appearance  of  ordinary  fat-cells.  Thus,  ex- 
amined at  the  bottom  of  the  follicle,  the  cells  are 
Biliary,  and  as  we  Advance  to  the  mouth  they  be- 


•^•' 

i  of  cray-fish. 


Hepatic 

come  fatty.     (Leiby.} 

The  comparative  anatomy  of  the  liver  is  repeated  in  its  order  of  devel- 
Development  opment  in  the  high  vertebrated  animals.  In  them  it  is  first 
of  the  liver,  detected  in  an  evolution  of  cells  upon  the  intestinal  wall,  at 
the  point  which  is  eventually  to  be  the  place  of  discharge  of  the  common 
bile-duct.  This  agglomeration  of  bile-cells  is  next  seen  to  project  or  bud 
off  through  the  intrusion  of  a  coecal  pouch.  In  the  amphioxus  the  con- 
dition thus  reached  remains  permanent,  and  is  the  counterpart  of  the  liver 
of  a  fowl  about  the  fourth  day  of  incubation.  The  coecal  pouch  next 
sends  forth  ramifications,  which  are  likewise  accommodated  with  cells, 
and  these,  branching  again,  give  origin  to  a  complicated  structure.  In 


STRUCTURE   OF  THE   LIVER. 


199 


.  sa 


this  condition,  the  mouth  of  the  ccecum  becomes  drawn  out  and  narrowed 
down,  and  so  forms  the  rudiment  of  an  hepatic  duct. 

In  man,  the  liver  is  the  largest  gland  in  the  body :  it  is  of  a  reddish- 
brown  color,  dense,  and  from  three  to  five  pounds  in  weight ;  Description  of 
convex  on  its  upper,  and  concave  on  its  inferior  surface.  It  the  liver- 
has  five  lobes :  the  right  lobe,  the  left  lobe,  the  lobus  quadratus,  the  lo- 
bus spigelii,  and  lobus  caudatus..  It  is  held  in  its  position  by  dupli- 
catures  of  peritoneum  and  by  a  fibrous  cord  termed  its  ligaments.  Its 
peritoneal  envelope  is  the  cause  of  its  glossy  appearance ;  its  cellular  en- 
velope extends  into  the  interior  as  sheaths  for  the  vessels.  Five  classes 
of  vessels  are  found  within  it :  the  branches  of  the  portal  vein,  those  of 
the  hepatic  artery,  those  of  the  hepatic  veins,  the  lymphatics,  and  the  he- 
patic ducts ;  the  latter,  converging  eventually  into  a  trunk,  the  hepatic 
duct,  joins  with  the  cystic  duct  to  form  the  ductus  communis  choledo- 

chus,  which  discharges  its  contents 
into  the  duodenum,  as  seen  in  Fig. 
83,  in  which  a  is  the  gall-bladder, 
which  constitutes  a  temporary  recep- 
tacle for  the  bile,  b  the  cystic  duct, 
d  the  hepatic  duct,  c  its  branches,  e 
the  ductus  choledochus,  and  h  its 
opening  into  the  duodenum. 

The  bile-ducts  entering  the  duodenum.  The  gaU^^der  ls  Wanting  in  in- 

vertebrated  animals,  and  first  makes  its  appearance  in  a  rudimentary 
condition  as  a  dilatation  of  the  bile-duct :  it  is  absent  in  the  horse,  pres- 
ent in  the  ox ;  in  the  camelopard  it  was  absent  in  one  individual,  and 
the  next  that  happened  to  be  examined  had  two. 

The  intimate  structure  of  the  liver  in  man  is,  in  many  particulars,  still 
imperfectly  known,  though  the  attention  of  the  most  eminent  Intimate  struc 
anatomists  has  been  devoted  to  it.  It  may,  however,  be  un-  ture  of  the  HV- 
derstood  that  each  hepatic  vein,  commencing  in  the  substance 
of  the  liver,  bears  upon  its  capillaries  small  portions  called  lobules,  from 
the  -J0-  to  the  -fa  of  an  inch  in  diameter,  in  a  manner  which  calls  to  mind 

the  arrangement  of  leaves  on  a  branch,  or 
a  bunch  of  grapes,  as  represented  in  Fig. 
84,  a  being  the  vein,  #,  £,  £,  leaf-like  lob- 
ules on  its  branches.  Excluding  the  lym- 
phatics, it  may  be  said  that  four  different 
systems  of  vessels  are  engaged  in  the  liver, 
the  portal  vein  and  hepatic  artery,  the  bile- 
ducts  and  hepatic  veins.  The  first  pair 
Hepatic  veins  in  the  lobules  of  the  liver.  are  afferent,  the  second  pair  efferent  ves- 
sels. The  portal  vein  brings  the  blood  from  which  bile  is  to  be  secre- 


200 


STRUCTURE   OF   THE   LIVER. 


Fig.  85. 


Origin  of  hepatic  veins  in  the  liver  lobules. 


ted  ;  the  hepatic  artery  brings  aerated  Wood  for  the  nourishment  of  the 
gland ;  the  bile-ducts  carry  away  the  biliary  secretion  which  has  been 
separated  from  the  portal  blood,  and  the  residue,  taken  charge  of  by  the 
hepatic  veins,  is  eventually  carried  back  into  the  general  circulation 
through  the  vena  cava. 

A  general  idea  of  the  mode  of  arrangement  of  the  four  vessels  in  the 

liver  may  be  obtained  by  recalling 
the  illustration  just  given,  that  the 
lobules  are  placed  on  the  commence- 
ment of  the  hepatic  veins,  like  grapes 
on  their  stalks.  The  vein  originates 
in  the  centre  of  each  lobule,  as  shown 
at  a  a,  in  Fig.  85,  and  exhibits  there 
a  ray-like  kind  of  divergence.  On 
the  periphery  of  each  lobule,  at  #,  5,  #, 
as  it  were  on  the  surface  of  the 
grape,  the  other  three  vessels  ram- 
ify. Of  them  the  portal  veinlets  dip 
down  into  the  substance  of  the  lob- 
ule. The  hepatic  arteries  likewise 
enter  for  the  purpose  of  giving  nutri- 
tion to  the  parts.  In  Fig.  86,  #,  a  are  the  commencing  hepatic  or  intra- 

lobular  veins  of  two  lobules  ;  £,  #, 
the  biliary  ducts  ;  c,  interlobular 
tissue ;  d  d,  parenchyma  of  the  lob- 
ules. With  respect  to  the  bile- 
ducts,  which  are  prominently  rep- 
resented in  this  figure,  it  is  not  pos- 
itively known  whether  they  pro- 
ceed beyond  the  surface,  and  the 
manner  in  which  they  are  related 
to  the  secreting  cells,  and  receive 
the  liquid  yielded  by  them,  is  a  sub- 
ject of  controversy.  The  inter- 
spaces between  the  capillaries  that  have  entered  the  lobules  are  filled  up 
with  these  cells. 

It  is  not  known  whether  the  hepatic  artery  discharges  its  blood  into 

He  atic  cells    ^  Porta^  capillaries,  or  into  those  of  the  hepatic  vein,  and, 

for  this  reason,  it  is  doubtful  whether  that  blood  takes  part 

in  the  secretion  of  the  bile.     The  secreting  cells  have  nucleolated  nuclei, 

and  are  about  the  -2  0*0  6  of  an  inch  in  diameter. 

In  Fig.  87,  at  <z,  #,  #,  their  normal  state  is  shown.     They  are  filled 
with  a  yellowish,  granular  soft  substance ;  at  b  b  is  the  appearance  of  fat 


I  T> 

Origin  of  bile-ducts  on  the  liver  lobules. 


COURSE   OF   THE   BILE.  201 

globules,  which  increase  in  number  and  size  at  c,  £,  <?,  c.  They  thus  con- 
tain both  biliary  material  and  oil  globules,  the  quantity  of  the  latter  vary- 
ST.  ing  with  the  nature  of  the  food,  and 

ffi\  sf^&i  *n  certani  Diseased  conditions  occur- 
'•.?.££.\  ('.-i^K*  rmg  to  so  great  an  extent  as  to  give 
rise  to  the  aspect  known  as  "fatty 
.liver."  This  accumulation  of  fat  is 
connected  with  the  respiratory  func- 
tion, not  only  in  conditions  of  dis- 
ease, but  even  in  a  state  of  health ; 

Hepatic  cells  magnified  400  diame'ters.  fQr?   t^e    more   energetic   the    rCSpira- 

tion,  the  more  free  is  the  liver  from  fat. 

As  the  chyle  passes  through  the  mesenteric  glands  before  it  is  dis- 
charged into  the  circulation,  so  do  the  matters  which  have  been  taken  up 
by  the  vascular  absorbents  pass  to  the  liver.  In  Chapter  IV.  the  bile, 
which  is  secreted  from  the  portal  blood,  is  treated  of  as  taking  part  in  the 
function  of  digestion ;  but  there  is  another  aspect  under  which  we  have 
now  to  regard  it. 

We  speak  of  the  circulation  of  the  blood,  because,  setting  out  from  the 
heart,  it  conies  back  thereto,  pursuing  a  course  which  returns  H  r  othetical 
upon  itself.  In  the  same  metaphorical  manner,  according  to  spiral  course  of 
the  views  of  some,  we  might  speak  of  the  spiral  motion  of  t 
the  bile ;  for  those  of  its  constituents,  which  are  first  taken  from  the  stom- 
ach and  small  intestine  by  their  veins,  appear  to  pass  in  the  portal  circu- 
lation to  the  liver.  In  that  gland  a  preliminary  partition  of  the  constitu- 
ents of  the  portal  blood  ensues,  one  stream  setting  off  to  the  general  cir- 
culation through  the  hepatic  veins,  and  another,  the  bile  itself,  returning 
to  the  intestine.  In  the  intestine  another  partition  ensues  ;  the  coloring 
matter  of  the  bile  is  dismissed  with  the  faeces,  and  the  residue,  taken  up 
by  the  lacteals,  passes  through  the  mesenteric  glands,  and,  either  by  the 
thoracic  duct  or  otherwise,  gets  into  the  blood  circulation.  It  may  there- 
fore be  perhaps  thought  that  the  constituents  of  the  bile  have  been  twice, 
in  close  succession,  in  the  digestive  cavity,  and  have  been  twice  absorb- 
ed, first  by  the  veins,  and  then  by  the  lacteals ;  and  that,  as  it  were,  a 
spiral  course  has  been  pursued. 

The  question  at  once  arises,  what  is  the  object  of  such  a  course  ?  Why 
is  there  this  return  to  the  digestive  cavity?  The  answer  commonly  given 
is,  the  bile  takes  part  in  promoting  the  operation  of  digestion.  But  the 
return  may  perhaps  be,  not  for  the  purpose  of  inducing  digestion,  but  for 
the  purpose  of  being  acted  on  or  digested  itself.  The  separation  of  its 
coloring  matter,  just  alluded  to,  is  a  significant  fact. 

The  portal  blood,  as  it  is  preparing  to  enter  the  liver,  may  be  regarded 
as  systemic  venous  blood,  the  constitution  of  which  has  been  altered 


202  SOURCE   OF  THE  BILE. 

through  the  additions  made  to  it  by  absorption  of  matters  from  the  stom- 
ach and  intestine.     We  may  overlook  for  the  present  those 

beparation  or  »••'».»** 

the  portal  blood  contributions  it  receives  from  the  veins  of  the  spleen  and  oth- 
m  the  liver.  er  S0urce3>  Regarding  it,  therefore,  as  systemic  venous  blood, 
charged  with  certain  of  the  products  of  digestion,  it  enters  the  liver  to  be 
acted  upon  by  that  gland.  The  first  effect  upon  it  is,  in  a  chemical  point 
of  view,  well  marked.  The  stream  which  sets  off  to  the  general  circula- 
tion through  the  hepatic  veins  may  be  said  to  carry  away  the  whole  of  the 
nitrogenized  material ;  for  the  bile,  which  is  at  this  point  parted  out  and 
sent  back  to  the  intestine  through  the  biliary  ducts,  does  not  contain  more 
than  4  per  cent,  of  nitrogen,  and  this  exclusive  of  the  water  which  im- 
Course  and  Parts  *°  ^  ^ts  liquid  condition.  Arrived  in  the  intestine,  a  rep- 
separation  of  etition  of  the  same  process  of  partition  takes  place,  the  color- 
ing matter,  which  contains  nearly  the  whole  of  this  residual  ni- 
trogen, being  dismissed  with  the  faeces,  and  the  remaining  hydrocarbon 
taken  up  by  the  lacteals  along  with  other  fats. 

The  first  duty  of  the  liver  is  therefore  a  separation  of  the  nitrogenized 
principles  of  the  portal  blood,  which  are  forthwith  carried  into  the  gen- 
eral circulation  through  the  hepatic  veins  and  the  vena  cava.  The  result 
is,  that  there  is  returned  to  the  intestine  a  sulphureted  hydrocarbon,  still 
containing  so  much*  nitrogen  as  to  form  a  very  unstable  product,  prone 
even  to  spontaneous  decomposition.  In  the  intestine  its  nitrogen  is  whol- 
ly removed  from  it,  and  the  combustible  hydrocarbon  is  then  absorbed. 

The  portal  blood,  regarded  under  the  aspect  here  presented,  is  obvi- 
From  what  ousty  composed  of  two  constituents :  1st.  Systemic  venous 
source  is  the  blood ;  2d.  Matters  obtained  from  the  digestive  cavity.  We 

bile  derived?    next  inquire  from  which  Of  these  ^  ft\Q  is  reaHy  derived. 

Besides  the  presumptive  evidence  arising  from  the  consideration  that 
if  the  bile  originated  from  matters  which  had  been  just  absorbed  from 
the  digestive  cavity,  it  would  be  inconceivable  why  it  should  be  returned 
forthwith  thereto,  its  quality  of  extreme  instability  marks  it  out;  as  a  sub- 
stance fast  approaching  to  final  disorganization  and  decomposition.  It 
bears  no  aspect  of  a  histogenetic  or  formative  body,  but,  on  the  contrary, 
it  is  on  the  downward  course.  We  should  scarcely  expect  to  recognize 
it  as  a  primary  product  of  the  digestive  action,  but  should  seek  its  prob- 
able origin  in  some  source  of  decay. 

Whatever  weight  may  attach  to  such  considerations,  we  have,  in  addi- 
tion, direct  evidence  which  places  the  source  of  the  bile  beyond  doubt  by 
referring  it  to  the  systemic  venous  blood,  and  not  to  the  matters  just  ob- 
tained from  the  digestive  cavity. 

During  foetal  life,  the  digestive  organs  are  in  an  inactive  state,  but  the 
liver,  which  is  largely  developed,  discharges  its  secretion  into  the  intes- 
tine. This  secretion,  which  is  known  as  the  meconium,  is  a  true  bile,  as 
the  following  analysis  proves. 


BILE   IS   DERIVED  FROM   VENOUS   BLOOD.  203 

Composition  of  Meconium.     (From  Simon.) 

Cholesterine 160.00 

Extractive  and  bilifellinic  acid 140.00 

Casein  340.00 

Bilifellinic  acid  and  bilin 60.00 

Biliverdin  and  bilifellinic  acid 40.00 

Cells,  mucus,  albumen 260.00 

1000.00 

Dr.  Davy  found  that  the  ash  left  after  the  incineration  of  a  sample  of 
rneconium  is  of  a  reddish  color,  consisting  chiefly  of  peroxide  of  iron  and 
magnesia,  with  a  trace  of  phosphate  of  lime  and  chloride  of  sodium. 

During  foetal  life  the  liver  is  therefore  discharging  the  same  function 
that  it  does  after  aerial  respiration  has  commenced,  that  is  it  does  not 
to  say,  it  secretes  bile  (meconium)  into  the  intestine ;  but  at 
this  period,  since  there  is  no  true  digestion,  the  -bile  can  products. 
come  from  one  source  alone,  and  that  source  is  the  systemic  venous 
blood.  There  therefore  can  remain  no  doubt  that,  in  after  life,  the  same 
effect  takes  place,  and  that  the  bile  is  never  derived  from  materials  which 
have  just  been  brought  from  the  digestive  cavities. 

I  therefore  regard  the  bile  as  an  excretion  of  materials  which  are  de- 
composing and  ready  to  be  removed  from  the  system.  I  in-  It  comeg  from 
cline  to  the  supposition  that  much  of  it  is  derived  from  the  the  venous 
cells  of  the  blood,  the  life  of  which  is  only  temporary,  for  the  blood* 
casein  of  the  meconium  is  nothing  but  the  globulin  of  the  cells,  the  two 
substances  being  chemically  allied,  and  the  predominance  of  iron  in  the 
ash  of  meconium  seems  to  establish  a  connection  with  hasmatrn.  More- 
over, this  opinion  is  supported  by  the  remarkable  stability  of  many  of 
the  nitrogenized  coloring,  matters,  the  analogies  between  hasmatin  and 
chlorophyl,  and  particularly  by  the  fact  that  in  the  herbivora  the  coloring 
matter  of  the  bile  is  undistinguishable  from  chlorophyl,  and  in  most  oth- 
er tribes  closely  allied  thereto. 

In  any  discussion  of  the  action  of  the  liver,  it  is  thus  to  be  constantly 
borne  in  mind  that  the  portal  blood  consists  of  two  distinct  portions,  sys- 
temic venous  blood  and  matters  absorbed  from  the  digestive  apparatus. 
Derived  from  the  first  of  these  portions,  we  trace  the  origin  of  the  bile  to 
the  waste  of  the  tissues,  or  to  the  blood-cells  on  their  downward  career ; 
and  hence  we  arrive  at  the  important  conclusion  that  every  proximate 
constituent  of  the  bile  pre-exists  in  the  systemic  venous  blood. 

Lehmann,  inclining  to  the  view  that  the  formation  of  the  bile  occurs 
in  the  liver  itself,  quotes  the  experiments  of  Miiller  and  Attempts  to  de- 
Kune,  who,  after  tying  the  portal  vein  and  applying  liga-  tect  cholic  acid 
tures  to  all  the  points  of  attachment  of  the  liver  in  frogs,  ex-  mentinthf" 
tirpated  that  organ,  and  collected  the  blood  of  those  which  blood- 
survived  the  operation  for  two  or  three  days,  by  amputating  their  thighs. 


204  CONSTITUTION   OF   BILE. 

It  was  expected  that  in  this  blood,  bile  pigment  and  cholic  acid  would 
be  found  if  the  original  formation  of  those  substances  took  place  exter- 
nally to  the  liver.  Such  did  not  prove  to  be  the  case.  It  may,  however, 
be  justly  inferred  that  no  reliable  conclusion  can  be  drawn  after  opera- 
tions of  such  magnitude  and  severity. 

The  alleged  inability  to  detect  the  constituents  of  the  bile  in  the  blood 
Cause  of  this  of  the  portal  vein  is  probably  due  to  the  defects  of  our  ana- 
Scting'biie  in~  ty^  processes,  for  it  is  very  clear  from  the  circumstance 
the  blood.  that  the  bile  which  is  poured  into  the  intestine  must  be  reab- 
sorbed,  with  the  exception  of  its  coloring  material,  either  by  the  lacteals 
or  the  veins,  or  by  both,  since  it  is  not  found  in  the  excrement.  Through 
whichever  of  these  channels  it  passes,  it  must  therefore  regain  the  gen- 
eral circulation,  for  it  can  not  be  supposed  that  in  the  short  period  of  its 
course  it  could  have  undergone  complete  metamorphosis. 

We  may  therefore  assume  that  the  proximate  ingredients  of  bile  pre- 
exist in  the  blood,  and  this  conclusion  is  enforced  by  the  fact  that,  after 
tying  the  vena  porta,  bile,  though  in  a  diminished  quantity,  is  still  se- 
creted. The  same  also  occurs  in  those  cases  of  malformation  in  which 
that  vessel,  instead  of  ramifying  into  the  liver,  empties  directly  into  the 
vena  cava.  When  there  is  any  failure  or  delay  in  the  removal  of  bile 
from  the  system,  the  effects  are  such  as  might  even  be  predicted,  nervous 
disturbance  ensuing,  and  eventually  all- the  symptoms  of  poisoning.  The 
circumstance  that  this  last  effect  often  takes  place  suddenly,  has  been  by 
some  supposed  to  be  dependent  on  the  necessity  for  the  bile  to  accumu- 
late, to  a  certain  extent,  but  it  is  much  more  likely  that  it  is  determined 
by  the  metamorphosis  of  the  decomposing  bile  having  reached  a  certain 
point,  when  special  poisonous  products  have  spontaneously  arisen  from  it. 

Bile,  from  whatever  animal  it  may  have  been  derived,  contains  a  resin- 
Constitution  of  ous  soda  salt,  a  coloring  material,  cholesterine,  and  mucus, 
bile.  rj^g  ac-(j  Q£  tjie  g0(^a  ga|t  -g  faQ  taurocholic  or  glycocho- 

lic.  The  coloring  matter  in  carnivorous  and  omnivorous  animals  is 
brown,  the  cholepyrrhin  of  Berzelius  ;  but  in  birds,  fishes,  and  amphibia, 
it  is  green,  biliverdin.  Strecker  makes  the  curious  remark  respecting  the 
bile  of  fishes,  that  in  those  which  are  of  salt  water,  potash  salts  predom- 
inate ;  and  in  those  of  fresh  water,  soda  salts.  Among  the  ultimate  ele- 
ments occurring  in  the  bile,  and  being  of  special  interest,  may  be  men- 
Constitution  of  tioned  sulphur,  which  exists  in  taurine,  of  which  the  com- 
taurine.  position  is  C4,  H7,  N,  S2,  O6.  It  may  be  obtained  from  ox- 

gall  ;  it  has  likewise  been  made  artificially  by  Strecker  from  the  isethi- 
onate  of  ammonia.  It  is  distinguished  by  evolving  sulphurous  acid 
when  burnt  in  the  open  air.  It  does  not  exist  in  the  bile  in  an  insu- 
lated condition,  but  probably  as  an  adjunct  to  cholic  acid,  and  has  been 
found  in  that  secretion  of  both  hot  and  cold-blooded  animals.  It  has, 


QUANTITY   OF   BILE.  205 

however,  been  asserted  that  sulphur,  and  therefore  taurocholic  acid,  does 
not  exist  in  the  bile  of  the  hog. 

The  bile  is  secreted  more  slowly  during  a  long  period  of  fasting,  and 
more  rapidly  during  normal  nutrition.  To  a  certain  extent,  production  of 
this  variable  rate  depends  on  the  general  principle  that  a  bile- 
gland  acts  more  energetically  in  proportion  as  the  supply  of  blood  sent 
to  it  is  greater.  If  not  wanted  for  the  present  purpose,  the  product  is 
stored  up,  for  a  time,  in  the  gall-bladder. 

When  the  bile  has  been  long  retained  in  the  gall-bladder,  it  becomes 
concentrated  through  the  removal  of  a  portion  of  its  water :  change  of  bile 
it  also  undergoes  a  change  of  color.  In  animals  whose  he-  after  retention, 
patic  bile  is  yellow  or  brown,  the  cystic  bile  has  a  tendency  to  green,  a 
change  of  color  dependent  on  partial  oxidation,  occasioned  by  the  arte- 
rial blood. 

The  flow  of  bile  takes  place  with  different  degrees  of  rapidity  at  dif- 
ferent diurnal  periods  :  thus  it  reaches  its  maximum  in  from  period  of  max 
thirteen  to  fifteen  hours  after  the  last  full  meal,  and  then  imum  flow  of 
rapidly  diminishes. 

Bidder  and  Schmidt  estimate  the  diurnal  secretion  in  an  adult  at  54 
oz.,  containing  5  per  cent,  of  solid  matter,  an  estimate  which  is  undoubt- 
edly too  high,  so  far  as  an  average  diet  and  state  of  health  are  implied. 
It  is  asserted  that  a  diet  of  flesh  tends  to  produce  more  bile  than  one  of 
a  purely  amylaceous  kind.  Even  the  use  of  a  large  quantity  of  water 
increases  its  amount,  and  this  as  regards  its  solid  constituents.  Reme- 
dial agents  act  in  various  ways.  Calomel  increases  the  fluid,  but  di- 
minishes the  solid  constituents.  Carbonate  of  soda  diminishes  both. 
Again,  there  are  great  variations  in  the  rate  of  its  production:  the  circum- 
stance just  mentioned,  that  its  maximum  flow  is  several  hours  after  the 
maximum  digestion,  is  important  as  regards  the  explanation  of  its  forma- 
tion, showing  significantly  that  it  is  not  directly  produced  from  matters 
recently  absorbed  from  the  intestine,  but  from  the  systemic  venous  blood. 

But  the  liver  has  other  duties  to  discharge  besides  the  separation  of 
bile.  It  gives  origin  to  sugar  and  fat,  as  is  proved  by  the  Other  duties  of 
circumstance  that  the  blood  of  the  hepatic  veins  is  richer  in 
those  ingredients  than  the  blood  of  the  portal.  In  this  re-  ing  bile, 
spect  its  action  seems  more  particularly  to  be  that  it  converts  other  sug- 
ars into  the  particular  form  known  as  liver-sugar,  which  it  can  also  pro- 
duce from  the  transforming  albuminous  bodies  ;  it  forms  fat  from  sugar, 
and  makes  from  certain  other  fats  the  special  one  known  as  liver-fat.  In 
this  duty  of  forming  sugar  and  fat,  it  exhibits  an  inverse  power  of  action ; 
as  the  production  of  the  one  predominates,  that  of  the  other  declines. 

From  the  .point  of  view  which  we  have  now  reached  through  this  de- 
scription, we  are  able  to  see  the  double  duty  which  this  great  gland  dis- 


206  BILE   BEHOVED   FROM   BLOOD   BY   FILTRATION. 

The  liver  does  charges,  and  must  correct,  to  a  certain  extent,  the  popular 
not  form  bile,  theory  of  its  action.  Does  the  liver  really  secrete  bile  ?  Is 
it  the  business  of  the  so-called  bile-secreting  cells  to  withdraw  the  constit- 
uents of  that  liquid  from  the  blood,  and  combine  them  together  into  this 
viscid  yellow  liquid  ?  I  think  not ;  for  it  is  a  matter  of  demonstration  that 
not  only  every  constituent  of  the  bile,  but  the  bile  itself,  pre-exists  in  the 
blood,  and  it  is  just  as  unphilosophical  to  burden  those  cells  with  the 
duty  of  forming  it  as  it  would  be  to  believe  that  a  like  agency  is  needful 
for  the  appearance  of  urea  in  the  kidney.  Moreover,  we  must  constantly 
bear  in  mind  the  extreme  instability  of  this  substance,  how  readily  the 
yellow  bile,  of  carnivorous  animals  becomes  green  by  partial  oxidation, 
and  the  green  bile  of  the  herbivora  yellow  by  deoxidation.  It  spontane- 
ously changes  in  its  downward  career,  and  any  differences  in  quality  or 
character  which  we  might  impute  to  the  action  of  the  cells  upon  it  may 
be  equally  well  attributed  to  its  own  inherent  principle  of  change. 

For  these  reasons,  I  believe  that  the  bile  simply  transudes  from  the 
Manner  of  blood,  and  that  the  cells  of  the  lobules  have  no  special  relation 
removing  it.  to  jt  beyond  this,  that  it  oozes  past  their  interstices,  or,  perhaps, 
by  *physical  imbibition,  finds  access  to  their  interior.  I  see  no  reason 
that  these  cells  should  form  it  when  it  pre-exists  in  the  blood,  nor  does 
the  state  of  the  affluent  and  effluent  blood  offer  any  contradiction  to  this 
conclusion.  In  all  discussions  of  the  functions  of  this  organ  founded 
upon  a  comparison  of  the  portal  and  hepatic  venous  blood,  the  relative 
quantity  of  water  which  they  contain,  and  its  great  and  even  rapid  fluc- 
tuations, should  always  be  borne  in  mind.  As  might  be  expected,  portal 
blood  contains  far  more  water,  and,  even  after  abundant  drinking,  the 
amount  in  the  hepatic  venous  blood  has  by  no  means  increased  to  the 
extent  that  might  have  been  expected.  It  is  for  these  reasons  that  the 
bile  varies  so  greatly  at  different  periods  in  its  specific  gravity  and 
fluidity. 

The  blood  of  the  portal  vein  is,  moreover,  periodically  varying  in  its 
Variation  in  constitution,  according  to  the  state  of  activity  of  the  organs 

tfoVorfoeJor-  from  wllich  i1:  is  tefog  derived-  In  tlie  first  stages  of  diges- 
tai  blood.  tion  the  stomach  is  supplying  it  in  unusual  quantities,  and 
with  the  ingredients  which  its  veins  have  been  absorbing  from  the  result 
of  histogenetic  digestion.  A  little  later,  the  same  thing  occurs  with  the 
intestine.  At  another  period  the  supply  from  the  spleen  varies. 

The  explanation  which  Mr.  Handfield  Jones  has  recently  given  of  the 
Function  of  the  function  of  the  hepatic  cells — that  they  manufacture  liver- 
hepatic  cells,  sugar — deserves  attentive  consideration,  more  particularly  if 
we  likewise  impute  to  them  the  production  of  liver-fat ;  for  this  would  at- 
tach them  rather  to  the  ramifications  of  the  hepatic  veins  as  a  part  of  their 
instrumental  mechanism,  and  assign  them  only  a  very  indirect  relation  to 


PRODUCTION  OF  FAT  AND  SUGAR.  207 

• 

the  bile-ducts.  The  contradictory  statements  whicii  have  been  made  by 
the  most  eminent  anatomists  respecting  the  connection  of  the  bile-ducts 
and  the  bile-cells — some  believing  that  the  bile-ducts  are  covered  inte- 
riorly with  the  cells ;  others,  that  the  ducts  end  on  the  outside  of  the 
lobules ;  others,  that  the  passages  reported  to  have  been  seen  among  the 
cells  are  interstitial  channels  and  not  proper  vessels — make  it  just  as 
probable,  anatomically,  that  the  cells  belong  to  the  hepatic  veins  as  that 
they  belong  to  the  biliary  ducts. 

It  is  true  that  there  may  be  a  mixed  action,  and  that  presence  of  bil- 
iary matter  may  be  necessary  to  the  sugar  and  fat  producing  agency. 
This  interworking  and  mutual  dependency  of  functions  is  not  without  a 
parallel.  Thus  the  lung,  viewed  as  a  secreting  or  excreting  gland,  has 
for  its  object  the  removal  of  carbonic  acid  from  the  system ;  but  it  also 
discharges  another  duty,  which  is  dependent  for  its  accomplishment 
upon  the  physical  or  chemical  qualities  of  the  hsematin  of  venous  blood, 
the  introduction  of  oxygen  by  aerating  or  arterializing.  But  the  excre- 
tion of  carbonic  acid  and  the  introduction  of  oxygen,  though  separate 
physiological  events,  and  to  be  spoken  of  as  distinct  functions  of  the 
lung,  are  yet  nevertheless  interconnected ;  the  one  is  essential  for  the  ac- 
complishment of  the  other,  and  the  one  effect  is  made  the  means  by 
which  the  other  is  brought  about. 

So  it  may  be  in  the  liver:  the  contact  of  bile  with  the  secreting  cells 
may  be  essential  to  their  sugar  or  fat  producing  action. 

The  deposit  of  fat  and  the  production  of  bile  seem  to  be  inversely  as 
each  other.  Bidder  and  Schmidt  found  that  fat  animals  Relation  of  the 
yield  less  bile  than  lean  ones,  and  that  when  they  were  fed 
on  fat  the  quantity  was  smaller  than  in  the  case  of  animals  of  bile, 
fed  on  a  less  fatty  diet.  From  such  facts,  the  inference  has  been  drawn 
that  the  accumulation  of  fat  is  in  consequence  of  a  diminution  of  the  se- 
cretion of  bile,  and  not  that  the  diminution  is  the  consequence  of  the  an- 
imal being  fat.  In  such  discussions  it  should,  however,  be  recollected, 
that  the  fats  do  not  furnish  all  the  substances  required  for  the  produc- 
tion of  bile,  but  only  a  limited  portion  thereof.  Thus  there  are  reasons 
for  the  belief  that  sugar,  lactic  acid,  or  some  other  allied  body  is  essen- 
tial to  that  process,  and  it  is  very  clear  that  so  too  are  the  materials 
furnished  from  the  decay  of  the  cells  of  the  blood. 

With  respect  to  the  production  of  sugar  in  the  liver,  it  may  be  re- 
marked, that  the  quantity  of  that  substance  in  the  solid  res-  production  of 
idue  of  the  serum  of  hepatic  blood  is  from  ten  to  sixteen  sugar  and  fat 
times  greater  than  in  the  same  residue  from  the  portal  blood ;  1] 

id  in  animals  undergoing  starvation,  though  no  sugar  could  be  found  in 

>rtal  blood,  it  occurred  to  such  an  extent  in  the  corresponding  hepatic 

lous  blood,  that  Lehmann  found  that  its  quantity  could  be  determined 


208  INFLUENCE   OF  PNEUMOGASTRIC  NERVE. 

• 

Iby  fermentation.  FrDm  this  there  can  be  no  doubt  that,  in  the  changes 
which  are  occurring  during  the  passage  of  the  blood  through  the  liver, 
there  is  a  production  of  sugar,  and  this  seems  to  be  connected  with  a  dim- 
inution in  the  quantity  of  fat ;  for  if  an  excess  of  fat  and  a  deficiency 
of  sugar  enter  that  organ,  and  their  quantities  are  inversely  changed  at 
their  emergence  from  it,  it  would  appear  that  fat  may  be  decomposed  act- 
ually, as  we  know  is  possible  hypothetically,  into  cholic  acid  and  sugar. 

But  with  respect  to  taurine,  the  adjunct  of  the  cholic  acid,  since  it  is  a 

Taurine  comes  m'trogenized  body,  we  are  obliged  to  seek  for  it  in  some  oth- 

from  blood-       er  source,  and  this,  it  would  appear  from  the  facts  set  forth, 

must  be  the  regressive  metamorphosis  of  the  blood-cells. 

Taurine  has  not  as  yet  been  detected  in  the  portal  blood.     It  can  not  be 

supposed  that  the  sulphuric  acid  of  the  portal  blood  is  used  by  deoxida- 

tion  in  the  preparation  of  free  sulphur  for  the  taurine,  since,  if  any  thing, 

the  quantity  of  that  acid  in  the  hepatic  venous  blood  is  increased.     From 

'whatever  source  it  may  have  been  derived,  the  sulphur  of  taurine  entered 

the  liver  in  an  unoxidized  state. 

When  we  reflect  that  the  bile  is  the  product  of  decay,  that  it  pre-ex- 
ists in  the  blood,  that  on  its  arrival  in  the  intestine  a  part  of  it  is  cast 
out  with  the  fa3cal  matter,  it  seems  very  unlikely  that  an  immense  cell 
apparatus,  constituting  the  largest  gland  in  the  whole  system,  should  be 
Analogies  in  necessary  for  its  removal.  But  when  we  moreover  reflect 
dlTdnglugar0"  that  in  tte  mechanism  of  plants,  from  gum,  or  rather  from 
and  fat.  carbonic  acid  and  water,  under  the  agency  of  cells  in  the 

leaves  or  other  structures,  both  sugar  and  oils  are  formed,  we  recognize 
that  there  is  a  connection  between  those  organisms  and  these  products. 

M.  Bernard's  experiments  seem  to  show  that  the  sugar-forming  func- 
Influence  of  tion  of  the  liver  may  be  morbidly  increased  by  wounding  the 
the  pneumo-  medulla  oblongata  near  the  origin  of  the  pneumogastric  nerve, 

gastric  nerve  °.  _r 

on  the  quanti-  or  by  the  application  of  galvanism  to  the  same  part,  an  arti- 
ty  of  sugar.  £cial  diabetes  ensuing,  and  this  within  a  few  minutes  after 
the  operation,  but  it  usually  ceases  after  two  or  three  days.  It  is  accom- 
panied by  a  great  derangement  of  respiration,  a  lowering  of  the  tempera- 
ture, and  a  venous  condition  of  the  arterial  blood.  It  by  no  means  fol- 
lows, however,  that  the  excess  of  sugar  observed  in  Bernard's  experi- 
ments arises  from  an  increased  action  of  the  liver,  or  an  increased  energy 
of  the  sympathetic  nerve :  it  may  be,  as  Reynoso  asserts,  attributable  to 
the  injury  inflicted  on  the  pneumogastric,  and  diminished  respiration. 
The  administration  of  ether  and  chloroform,  the  conditions  of  old  age  and 
foetal  life,  the  influence  of  many  diseases,  as  chronic  bronchitis,  asthma, 
pleurisy,  all  present  a  tendency  to  the  accumulation  of  sugar  in  the  urine, 
the  sources  in  each  of  these  cases  being  attributable  to  respiratory  dis- 
turbance ;  for  if  any  thing  occurs  to  retard  or  delay  the  destruction  by 


DESTRUCTION   OF    BLOOD-CELLS   IN   THE   LIVER.  209 

oxidation  of  the  sugar,  constantly  formed  by  the  liver,  the  accumulation 
will  make  its  appearance  in  the  urine.  The  appearance  of  saccharine 
matter  in  that  secretion  may  be  equally  well  attributed  to  its  non-de- 
struction in  the  system  generally  as  to  its  over-production  by  the  liver. 

This  gland,  besides  producing  sugar  and  fat,  is  the  seat  in  which  the 
worn-out  blood-cells  are  finally  disintegrated,  and  probably  Destruction  Of 
the  young  ones  pushed  forward  through  a  certain  stage  of  blood-cells  in 
their  development ;  advantage,  moreover,  being  incidentally  t 
taken  of  the  secreted  bile,  which  possesses  properties  useful  though  not 
essential  for  promoting  the  digestion  and  absorption  of  fatty  material, 
perhaps,  also,  of  imparting  a  definite  course  to  the  transmutation  of  the 
semi-digested  material  in  the  intestine,  and  this  both  as  regards  nitro- 
genized?  amylaceous,  and  fatty  bodies.  Of  the  influence  of  the  bile  in 
promoting  the  absorption  of  fat,  the  physical  experiments  which  have 
been  alluded  to  leave  no  doubt;  but  that  these  uses  are  of  a  secondary 
or  non-essential  kind,  and  are  only  taken  advantage  of  in  an  indirectly  eco- 
nomical way,  is  established  beyond  all  possibility  of  a  doubt  by  the  fact 
that  animals  can  live  for  a  long  time,  even  for  months,  without  the  pas- 
sage of  bile  into  the  intestine,  provision  having  been  made  for  its  escape 
externally  through  an  artificial  fistulous  orifice. 

These  conclusions  respecting  the  functions  of  the  liver  are  in  harmony 
with  the  appearances  presented  by  the  blood  leaving  and  entering  it : 
the  predominance  of  colorless  blood-cells,  and  of  young  cells  well  ad- 
vanced toward  perfection  in  the  former,  and  of  wasted,  worn-out  ones  in 
the  latter ;  with  the  fact  that  the  maximum  secretion  of  bile  does  not 
take  place  until  more  than  half  a  day  after  the  ingestion  of  food ;  and 
that  during  foetal  life,  in  which  there  is  no  food,  either  in  the  stomach  or 
intestine,  to  be  digested,  the  liver  is  nevertheless  in  high  activity,  and 
bile  is  secreted. 

In  view  of  all  the  preceding  facts,  we  may  therefore  finally  conclude 
that  there  are  at  least  four  distinct  operations  conducted  in  the  liver;  1. 
The  production  of  sugar  and  fat ;  2.  The  separation  of  the  bile ;  3.  The 
destruction  of  old  blood-cells  ;  4.  The  completion  or  perfection  of  young 
blood-cells,  perhaps  by  receiving  their  iron.  With  respect  to  these  it 
may  be  remarked, 

First.  The  formation  of  sugar  and  fat,  either  from  carbohydrates,  or 
what,  in  this  instance,  is  more  probable,  from  albumenoid  bod-  General  sum- 
ies  brought  by  the  portal  vein,  can  no  longer  be  doubted. 
The  prevalence  of  liver-sugar  and  liver-fat  in  all  that  region  er. 
of  the  venous  circulation  included  between  the  liver  and  the  lungs  must 
be  attributed  to  this  source.  That  the  sugar  undergoes  rapid  metamor- 
phosis in  the  pulmonary  organs  is  plainly  proved  by  the  effects  of  irri- 
tation of  the  pneumogastrics,  which,  interfering  with  the  function  of  rcs- 

O 


210          SUMMARY  OF  THE  ACTION  OF  THE  LIVER. 

piration,  permit  this  substance  to  reach  the  aortic  circulation,  from  which 
it  is  removed  by  the  kidneys,  a  diabetes  arising.  So  far  as  the  prepara- 
tion and  course  of  this  sugar  is  concerned,  the  liver  is  a  ductless  gland, 
and,  with  Mr.  Handfield  Jones,  I  believe  that  the  cells  of  the  liver  are  the 
agents  which  accomplish  this  duty.  The  production  of  fat  appears  to  be 
inversely  as  that  of  sugar.  In  the  crustacean  bile-sac,  Fig.  82,  we  see 
the  gradual  stages  of  its  appearance ;  and  the  production  of  both  bodies 
.is  well  illustrated  in  the  life  of  plants. 

Second.  The  bile  is  separated  from  the  blood  portion  of  the  portal 
blood,  and  not  from  the  products  of  digestion  obtained  from  the  chylo- 
poietic  viscera.  The  elements  of  bile  I  believe  to  pre-exist  in  the  blood, 
and  to  escape  from  the  portal  veinlets  to  the  biliary  ducts  by  mere  filtra- 
tion or  strainage.  The  precise  source  from  which  the  bile  is  derived 
is  probably  the  blood- cells,  and  in  the  changes  which  they  are  under- 
going the  spleen  is  perhaps  concerned.  If  this  be  so,  the  bile-duct  is 
as  much  a  duct  for  the  spleen  as  it  is  for  the  liver  itself.  The  bile  may 
almost  be  looked  upon  as  a  hydrocarbon,  containing  a  very  changeable 
and  therefore  noxious  coloring  material,  which,  when  the  secretion  reach- 
es the  intestine,  is  parted  from  it  and  dismissed  with  the  fteces,  the  prop- 
er hydrocarbon  being  taken  up  by  the  absorbing  arrangement  for  hydro- 
carbons, the  lacteals,  and  so  sent  through  the  thoracic  duct.  Perhaps, 
also,  by  reason  of  its  special  adaptedness  for  that  purpose,  it  aids  in  the 
absorption  of  other  fats. 

At  this  point  it  may  be  remarked  that  the  view  here  presented  of  the 
sugar-forming  and  bile-straining  functions  of  the  liver  appears  to  be 
greatly  strengthened  by  the  anatomical  construction  of  that  organ. 
There  is  no  obvious  communication  between  the  portal  and  hepatic  vein- 
lets  save  through  cells,  but  the  portal  veins  and  the  bile-ducts  run  in 
their  ramifications  side  by  side. 

Third.  Whatever  part  of  the  disintegration  of  old  blood-cells  takes 
place  in  the  spleen,  their  final  destruction  is  doubtless  accomplished  in 
the  liver,  this  being  the  immediate  source  from  which  the  bile  itself  is 
derived.  Though  these  metamorphoses  are,  to  a  greater  or  less  extent, 
occurring  throughout  the  circulation,  it  is  in  these  two  great  glands  that 
an  opportunity  is  afforded  for  the  destruction  to  reach  it's  completion,  and 
the  resulting  product  of  waste  to  be  removed ;  nor  is  there  any  thing  in 
this  view  at  all  contradictory  to  the  opinion  I  have  enforced,  that  all  the 
constituents  of  the  bile  may  be  found  in  the  general  circulation. 

Fourth.  The  liver  also  aids  in  the  preparation  or  maturation  of  young 
blood-cells  in  an  indirect  way.  There  are  certain  of  the  mineral  constit- 
uents of  the  disintegrated  cells  too  valuable  to  be  cast  away,  since  they 
can  subserve  the  duty  of  entering  into  the  composition  of  young  cells 
passing  toward  perfection.  As  such  a  substance  may  be  mentioned  iron. 


THE   DUCTLESS   GLANDS.  211 

This  view  of  the  action  of  the  liver  appears  also  to  "be  sustained  by  the 
large  number  of  star-like  and  corrugated  blood-cells  occurring  in  the 
pgrtal  blood  of  fasting  animals,  and  which  are  replaced  by  such  as  appear 
to  be  young  and  perfect  in  the  blood  of  the  hepatic  veins.  It  is  not, 
however,  to  be  supposed  that  all  the  iron  is  economized  in  this  manner ; 
a  considerable  portion  of  it  accompanies  the  pigment  as  an  essential  in- 
gredient, and  is  finally  discharged  through  the  intestine. 

OF  THE  DUCTLESS  GLAOT)S. 

The  salivary  and  sudoriparous  glands  discharge  their  secretion  directly 
through  ducts.  The  liver  and  kidneys  have  upon  their  ducts  The  ductless 
an  additional  mechanism,  the  gall  bladder  in  the  one  case,  and  glands. 
the  urinary  in  the  other,  which  serve  as  receptacles  for  storing  up  the 
product  of  action  in  a  temporary  manner,  and  so  converting  the  continu- 
ous effect  of  the  gland  into  a  periodical  result.  In  each  of  these  instances 
we  may  arrive  at  conclusions  of  a  certain  degree  of  exactness  respecting 
the  functions  and  use  of  the  gland  from  a  study  of  the  secretion  it  yields  ; 
but  there  are  in  the  system  other  glandular  organs  which  differ  essen- 
tially from  all  the  preceding  in  not  being  furnished  with  ducts.  These 
are  the  spleen,  the  thymus  and  thyroid  glands,  and  the  supra-renal  cap- 
sules. 

Much  diversity  of  opinion  prevails  respecting  the  true  nature  and  ac- 
tion of  these  bodies.  From  their  structure  bearing  a  resent  Their  supposed 
blance  to  that  of  the  preceding,  with  the  exception  of  the  ab-  functions, 
sence  of  a  duct,  many  have  thought  that,  like  them,  they  are  really  secret- 
ing organs.  Others  have  supposed  that  they  have  a  relation  to  the  nu- 
trition of  the  system,  in  giving  origin  to  the  development  of  cells,  or  that 
they  are  connected  with  the  organization  of  the  blood  itself;  and  that 
such  is  their  duty  is  perhaps  rendered  probable  by  the  circumstance  that 
some  of  them,  as  the  thymus  and  thyroid,  exhibit  their  utmost  develop-, 
ment  when  the  body  is  rapidly  growing,  and  diminish  when  maturity  is 
reached.  That  they  enjoy  a  community  of  action,  or  that  their  function 
can  be  vicariously  discharged  by  other  organs,  has  been  clearly  estab- 
lished by  the  result  of  operations  in  which  one  or  other  of  them  has  been 
extirpated. 

With  respect  to  the  spleen,  the  views  of  Professor  Kolliker  are  sup- 
ported by  many  facts.  He  supposes  that  one  of  the  chief  func-  Function  of 
tions  of  that  gland  is  the  dissolution  of  the  disorganizing  blood-  the  sPleen- 
cells  preparatory  to  the  action  of  the  liver,  in  which  ha3matin  is  to  be 
converted  into  the  coloring  matter  of  the  bile.  In  the  discussion  entered 
into  respecting  the  origin  of  the  bile,  we  have  come  to  the  conclusion 
that  it  is  derived  from  the  systemic  venous  blood,  and  in  the  supposition 
here  presented  respecting  the  function  of  the  spleen  there  is  nothing  con- 


212 


THE   SPLEEN. 


tradictory,  for  it  is  to  be  remembered  that  the  blood  of  the  spleen  is  a 
constituent  of  the  portal  circulation.  It  also  appears  to  be  a  general 
Opinion  that  the  spleen  likewise  maintains  a  mechanical  relation  to  the 
portal  mechanism  by  serving  as  a  receptacle  for  any  excess  of  blood, 
and  thus  relieving  the  vessels  of  pressure,  or  by  acting  in  like  manner 
when  there  is  any  obstruction  to  the  passage  of  blood  through  the  liver. 

As  our  knowledge  of  the  action  of  the  ordinary  glands  becomes  more 
Analogy  of  the  accurate,  the  function  of  the  ductless  glands  loses  much  of 
S^ttMdncfe-  its  Peculiarit7-  As  we  have  already  stated,  in  a  certain 
less.  sense  the  liver  itself  may  be  said  to  be  a  ductless  gland,  for 

it  appears  to  be  one  of  the  constant  duties  of  that  organ  to  prepare  sugar 
from  materials  in  which  it  did  not  pre-exist.  And  this  sugar  does  not 
escape  through  the  hepatic  ducts  in  company  with  the  bile,  but  is  taken 
directly  into  the  system  through  the  hepatic  veins.  But  this  principle 
of  action  is  identically  what  occurs  in  the  case  of  every  ductless  gland, 
and  hence  it  may  be  inferred  that  the  changes  which  these  impress  on  the 
blood  are  necessary  for  the  development  and  nutrition  of  the  system.  If 
the  doctrine  of  Kolliker,  be  correct,  the  spleen  is  only  an  appendix  to  the 
liver,  and  the  same  duct  answers  as  a  common  outlet  for  both. 

The  views  here  alluded  to  are  enforced  by  the  examinations  which 
Nature  of  have  been  made  of  the  blood  of  the  splenic  vein.  The  fol- 
spienic  blood.  lowing  table  exhibits  the  contrast  between  it,  that  of  the  ex- 
ternal jugular,  and  that  of  the  mammary  artery. 

Constitution  of  Splenic  Blood.     (From  Scherer.") 


Mammary  Artery. 

Ext.  Jugular. 

Splenic  Vein. 

Water 

750.60 

778.90 

746  30 

Albumen  

89.50 

79.40 

124.40 

Corpuscles  and  Fibrin.... 
Loss  

159.90 

141.70 

128.90 
.40 

1000.00 

1000.00 

1000,00 

,.  From  which  it  appears  that  the  blood,  after  circulating  through  the 
spleen,  has  lost  a-  large  portion  of  its  cells,  the  relative  quantity  of  its 
albumen  is  greatly  increased,  and,  moreover,  from  being  the  basic  albu- 
minate  of  soda,  the  form  under  which  it  ordinarily  occurs  in  the  blood, 
it  has  become  the  neutral  albuminate,  as  is  proved  by  a  turbid  appear- 
ance on  the  addition  of  water,  and  this  state  it  seems  to  retain  during 
the  portal  circulation,  for  the  blood  of  the  hepatic  veins  exhibits  the  same 
peculiarity. 


OF   EXCRETION.  213 


CHAPTER  XII. 

OF  EXCRETION. 

THE  URINE,  MILK,  AND  CUTANEOUS  EXCRETIONS. 

Secretion  and  Excretion. 

Of  the  Kidney:  its  Structure  and  Functions. — The  Malpighian  Circulation. —  The  Urine:  its  In- 
gredients, their  Variations  and  Sources. — Abnormal  Substances  in  it. —  The  Water  and  Salts 
exude  by  Filtration. — The  Cells  remove  unoxidized  Bodies. — Manner  of  Removal  of  the  Liquid 
from  the  Malpighian  Sac. 

Of  the  Mammary  Gland:  its  Structure. —  Colostrum  and  Milk. — Ingredients  of  Milk  and  their 
Variations. — Influence  of  Diet. — Inquiry  into  the  Origin  of  the  Ingredients  of  the  Milk,  its  Fat, 
Casein,  Salts,  Sugar. — Manner  of  Action  of  the  Gland  by  Strainage. 

Of  the  Skin. — Structure  of  its  Epiderma  and  Derma. — Sudoriparous  and  Sebaceous  Glands. — 
Nails. — Hair. — Ingredients  of  Perspiration. — Exhalation:  its  Amount. —  Causes  of  the  Vari- 
able Action  of  the  Skin. — Its  Double  Action. — Absorption  by  the  Skin. — General  Summary  of 
the  Cutaneous  Functions.  + 

THE  function  of  secretion  is  very  commonly  treated  of  by  physiolo- 
gists under  two  divisions,  secretion  and  excretion.  The  Distinct;on  be 
former  refers  to  the  separation  from  the  blood  of  those  fluids  tween  secretion 
which  are  required  for  the  uses  of  the  body,  and  which  are 
therefore  still  retained ;  the  latter,  to  those  which  are  effete,  and  to  be 
cast  out  as  excrementitious  matter.  Of  secretions,  the  saliva  or  the  pan- 
creatic juice  may  be  taken  as  examples  ;  of  excretions,  the  urine.  4 

But  this  subdivision  is  only  one  of  convenience,  and  has  no  natural 
foundation.  The  so-called  secretions  are,  in  many  instances,  far  from 
being  more  highly  elaborated  bodies ;  in  reality,  they  are  often  on  their 
descending  career.  And  among  excretions,  if  milk  be  enumerated,  as  it 
ought  to  be,  since  it  is  a  dismissed  product  of  the  system  preparing  it, 
we  have,  instead  of  an  excrementitious,  a  pre-eminently  nutritive  body. 

Nevertheless,  since  this  manner  of  considering  the  subject  offers  con- 
siderable conveniences,  I  have  resorted  to  it  for  the  preceding  and  pres- 
ent chapters.  In  this  I  shall  accordingly  treat  of  the  urine,  the  milk, 
and  the  products  removed  by  the  skin. 

OF  THE  KIDNEYS. 

The  products  of  waste  arising  from  oxidation  in  the  functional  activity 
of  the  system,  and  which  are  of  a  non-gaseous  kind,  the  use-  „, 

J  '  .  Physical  func- 

less  materials,  saline  or  otherwise,  which  have  been  absorb-  tion  ofthekid- 
ed  in  the  digestive  tract,  and  carried  into  the  circulation,  ne7' 
must  be  removed.      Gaseous  substances  and  vapors  may  pass  away 
through  the  lungs,  but  solid  material  must  be  excreted  in  a  state  of  so- 


214  STRUCTURE  OF  THE  KIDNEY. 

lution  in  water.  To  accomplish  tins  object,  a  special  mechanism,  the 
kidney,  is  introduced. 

From  this  manner  of  considering  the  functional  duty  of  the  kidney,  it 
is  very  clear  that  a  special  relation  must  exist  between  this  excreting  or- 
gan and  the  respiratory  mechanism,  for  in  the  case  of  animals  which 
breathe  by  gills,  or  in  those  which,  though  subsequently  atmospheric 
breathers,  receive  their  supply  of  aerated  blood  before  birth  by  a  placenta, 
the  conditions  under  which  aeration  takes  place  are  such  as  permit  the 
removal  of  solid  material  by  the  respiratory  mechanism.  The  urinary 
excreting  apparatus  of  an  animal  breathing  air  is  therefore  necessarily 
burdened  with  an  exclusive  duty,  which  is  shared  by  the  gills  and  the 
skin  in  a  water-breather. 

In  fishes,  the  renal  apparatus  is  constructed  under  the  condition  here 
The  kidnev  in  indicated,  and  though  in  many  it  appears  to  be  greatly  de- 
birds,  fishes,  veloped,  extending  as  a  tubular  arrangement  from  the  skull 

cts,  etc.  through  the  abdominal  cavity,  it  is  to  be  regarded  as  analo- 
gous to  theWollfian  bodies  rather  than  to  the  true  kidney.  In  reptiles 
the  proper  kidneys  appear ;  in  birds  they  are  well  developed,  but  their 
secretion  is,  for  the  most  part,  a  semi-solid  substance,  chiefly  urate  of 
ammonia.  The  tubular  form  is  presented  in  both  insects  and  arachni- 
dans,  discharging  its  secretion  into  a  cloaca. 

In  man  the  kidneys  may  be  described  as  a  pair  of  dark-red  ovoid  bod- 
The  kidneys  in  ies?  placed  one  on  each  side  of  the  vertebral  column,  in  the 
man-  lumbar  region,  the  right  kidney  being  a  little  lower  than  the 

left.  In  the  adult  the  kidney  is  four  or  five  inches  in  length,  and  is  en- 
veloped in  a  mass  of  fat.  Blood  is  brought  from  the  aorta  to  supply  the 
organ  by  the  renal  or  emulgent  artery,  and  is  carried  back  by  the  emul- 
gent  vein  into  the  inferior  vena  cava.  During  its  passage  through  the 
kidney  there  is  removed  from  the  Wood  a  liquid  secretion,  the  urine, 
which*,  flowing  down  a  long  channel,  the  ureter,  is  emptied  into  the  blad- 
der, from  which  it  may  be  periodically  removed. 

The  supra-renal  capsules  are  bodies  of  a  yellow-red  color  placed  above 
Supra-renal  the  kidneys.  They  are  much  larger  in  the  foetus  than  in  the 
capsules.  adult,  and  doubtless  have  a  reference  to  the  peculiar  conditions 
of  respiration  obtaining  at  that  time,  for,  as  we  have  just  observed,  the 
renal  and  respiratory  mechanisms  are  necessarily  interconnected. 

The  substance  of  the  kidney  is  described  as  consisting  of  two  por- 
Minute  strnc-  ^^ons»  tne  cortical  and  the  medullary  or  tubular,  as  seen  in 
ture  of  the  kid-  Fig.  88,  in  which  1  is  the  supra-renal  capsule ;  2,  the  vascu- 
lar portion  of  the  kidney;  3,  3,  tubular  portion  grouped  into 
cones ;  4,  4,  papillae  projecting  into  calices ;  5,  5,  5,  the  three  infundi- 
bula ;  6,  the  pelvis  ;  7,  the  ureter.  (Wilson.)  From  which  it  appears 
that  the  cortical  substance  is  the  external  portion,  and  the  tubular  is 


THE  MALPIGHIAN   CORPUSCLES. 


215 


Section 


grouped  into  cones,  the  base  of  each  cone  being 
outward,  and  the  point  toward  the  pelvis  of  the 
kidney.  The  cortical  substance,  however,  envel- 
ops the  cones  nearly  to  their  points.  It  is  of  a 
red  color,  and  is  the  seat  of  the  secreting  action. 
The  urine,  as  it  arises,  passes  along  the  fine  con- 
vergent vessels,  the  uriniferous  tubes,  and  these, 
coalescing  as  they  approach  the  points  of  the  cones, 
give  origin  to  what  are  termed  the  ducts  of  Bellini. 
From  these  the  secretion  passes  into  the  calices, 
thence  into  the  pelvis,  and  so  along  the  ureter  into 
the  bladder.  In  the  cortical  substance  there  are 
large  numbers  of  dark  points,  the  Malpighian  bod- 
kidney.  ies.  Their  diameter  is  about  -j-Lj-  of  an  inch. 
Mr.  Bowman  has  demonstrated  that  the  minute  structure  of  the  cortical 
portion  is  as  follows  :  The  uriniferous  tubes,  as  they  approach  it,  under- 
go bifurcation  in  such  a  way  that  the  branches  continually  arising  have, 
for  the  most  part,  a  diameter  of  about  -^-$  of  an  inch.  As  they  enter  it 
they  are  contorted,  and  at  their  ends  present  small  capsules  or  flask- 
shaped  sacs.  Each  of  the  capsules  is  entered  by  a  twig  of  Str*uctureofthe 
the  renal  artery,  which  at  once  divides  into  loop-like  branch-  Malpighian 
es  constituting  a  tuft,  and  which  delivers  the  blood  to  a  corPus 
vein  originating  in  the  interior  of  each  tuft.  These  structures  are  known 
as  the  Malpighian  corpuscles.  The  vein  and  artery  pass  out  of  the  cor- 
puscles usually  at  the  same  point ;  the  vein,  however,  instead  of  deliv- 
ering its  blood  at  once  to  the  renal  vein,  forms  a  plexus  on  the  sides  of 
a  uriniferous  tube,  in  this  simulating  the  mechanism  of  the  portal  vein, 
which  begins  in  a  capillary  system  and  ends  in  one.  It  is  supposed  that 
the  exudation  of  the  water  of  the  urine  takes  place  in  the  Malpighian 
body,  and  the  secretion  of  the  solid  portions  from  the  cells  which  cover 
the  uriniferous  tubes. 

The  chief  feature  of  this  structure  is,  therefore,  that  in  a  sac  formed 
upon  a  uriniferous  tube,  a  tuft  of  capillaries,  the  walls  of  which  are  of  ex- 
treme tenuity,  permits  water  to  escape  from  the  blood  supplied  by  the 
emulgent  artery.  The  blood,  thus  concentrated  by  loss  of  its  water, 
passes  into  the  veinlets  which  originate  in  the  interior  of  the  tuft ;  these, 
converging  into  a  little  trunk,  less  in  diameter  than  the  twig  Circulation  of 
of  the  emulgent  artery,  escape  along  with  that  vessel  from  thebioodinthe 
the  capsule  ;  but,  instead  of  discharging  its  contents  into  the  kidne^- 
renal  vein,  it  ramifies  in  a  plexus  on  the  walls  of  a  uriniferous  tube,  thus 
affording  a  miniature  representation  of  the  portal  vein,  beginning  in  a 
capillary  system  and  ending  in  one.  From  the  plexus  the  commencing 
capillaries  of  the  renal  veins  arise. 


216 


THE   MALPIGHIAN   CORPUSCLES. 


90. 


Some  anatomists  suppose  that  the  Malpighian  capsule  is  not,  in  reality, 
a  flask-like  expansion  of  the  uriniferous  tube, 
but  that  the  tube,  dilating,  folds  over  the  blood 
capillaries,  and  so  receives  them.  However 
that  may  be,  they  form  a  loose  ball  in  its  in- 
terior, fastened  to  it  only  by  the  arterial  twigs 
and  its  corresponding  and  juxtaposed  vein. 

The  foregoing  description  is  illustrated  by 
the  annexed  figures,  Fig.  89  being  half  dia- 
grammatic, from  Kolliker.  1,  a  Malpighian 
capsule,  A,  with  the  tubulus  uriniferus,  B,  C, 
springing  from  it ;  a,  membrane  of  Malpighian 
body,  continuous  at  b  with  the  membrana  pro- 
pria  of  convoluted  tubule;  c,  epithelium  of 
Malpighian  corpuscle;  d,  that  of  tubule;  e, 
detached  epithelium ;  f,  vas  afferens ;  g,  vas 
efferens ;  A,  glomerulus  Malpighianus  :  2,  three 
naif  diagram  of  human  Malpighian  epithelial  cells  from  convoluted  tubule,  magni- 

corpuscle,  magnified  300  diameters.    fied  g5Q  diameters— OD6  with  oil  drops. 

Fig.  90,  Glomerulus,  or  tuft  of  blood-vessels  from  the  innermost  part 
of  the  cortex  of  the  kidney  of  the  horse:  #, 
arteria  interlobularis ;  a/,  vas  afferens ;  m  m, 
glomerulus ;  ef,  vas  efferens ;  b,  divisions  of 
arteriola  recta  in  the  medullary  substance. 

Fig.  91  shows  the  ciliated  epithelium  of  the 
uriniferous  tube  in  the  frog:  a,  cavity  of  the 
uriniferous  tube ;  5,  its  epithelium  ;  b',  ciliated 
portion  thereof;  b",  de- 
tached ciliated  epithelial 
cell ;  c,  basement  mem- 
brane of  the  tube ;  cf, 
that  of  the  capsule ;  m, 
capillaries  of  the  tuft ; 
t,  adjacent  uriniferous 
tube. 

Mr.  Bowman's  expla- 
nation of  the  Malpighi- 
an circulation  is  repre- 
sented in  Fig.  92.  a, 
branch  of  renal  artery ; 
of,  afferent  vessels ;  m, 
m,  Malpighian  tufts ;  ef, 
eft  efferent  vessels ;  p, 


Fig.  91. 


Glomerulus  from  the  horse,  magni- 


Cilia  on  uriniferous  tube  of  frog. 


THE   MALPIGHIAN   CORPUSCLES. 


217 


Fig.  92. 


Diagram  of  Malpjghian  circu-  T  .  .  . 

lation.  es.     Dr.  Isaacs  s  in- 

vestigations are  entirely  confirmatory  of 
Mr.  Bowman's  views,  so  far  as  structure 
is  concerned.  Fig.  93  is  a  view  obtained 
by  agitating  scrapings  of  the  kidney  of  a 

~     04 


their  plexus  upon  the  uriniferous  tube  ;  st,  straight 
tube  ;  ct,  convoluted  tube. 

I  am  indebted  to  Dr.  Isaacs  for  the  following  in- 
structive figures  and  descriptions  from  his  paper  read 
before  the  Academy  of  Medicine.  His  method  of 
examination  of  the  Fig.  93. 

minute  mechanism 
of  the  kidney,  by 
rendering  small  por- 
tions of  it  transpa- 
rent, greatly  facili- 
tates these  research- 


tuft  with  uriniferous  tube, 

nified  75  diameters. 


Ruptured  Malpighian  coil  of  the  deer,  magnified  80  diameters. 


Fig.  95 


Nucleated  cells  c  i  coil,  magnified  80  diameters. 


sheep  (which  had  pre- 
viously been  injected 
with  chrome  yellow 
and  sulphuric  ether)  in 
a  test-tube  with  water. 
The  portion  on  the  left 
shows  the  tuft  alone, 
that  on  the  right  its 
reception  in  the  urinif- 
erous capsule. 

Fig.  94  shows  the 
artery,  filled  with  in- 
jection, and  the  Mal- 
pighian coil  or  tuft  rup- 
tured in  the  capsule. 
The  injected  material 
lies  in  broken  portions. 
Fragments  of  the  in- 


218  THE    UEINE. 

jected  vessels  of  the  coil  are  seen  passing  down  the  tube.  From  the 
kidney  of  the  deer. 

A  difference  of  opinion  prevails  among  anatomists  as  to  the  existence 
of  nucleated  cells  upon  the  Malpighian  tuft  or  coil  in  the  case  of  the  higher 
animals.  This  question  is  finally  settled  by  Dr.  Isaacs  in  the  following 
manner.  An  ethereal  or  watery-colored  solution  is  injected  into  the  ure- 
ter, so  as  to  distend  the  tubes,  burst,  and  throw  off  the  capsule.  The 
cells  can  then  be  seen  upon  the  naked  tuft  or  coil.  Fig.  95  shows  the 
Malpighian  body  and  uriniferous  tube  of  the  kidney  of  the  black  bear. 
The  artery  had  been  first  partially  filled  with  injection,  which  had  broken 
the  coil  in  pieces.  The  injection  from  the  ureter  ruptured  the  capsule, 
which  is  seen  in  shreds.  Nucleated  cells  are  seen  on  the  naked  coil  or  tuft. 
In  the  upper  part  of  the  figure,  to  the  left,  is  a  broken  tuft,  on  the  right  of 
which  the  ruptured  capsule  is  perceived,  and  nucleated  cells  upon  the 
uncovered  tuft.  In  the  upper  part  of  the  figure,  to  the  right,  are  the 
fragments  of  a  Malpighian  tuft,  with  nucleated  cells  adhering  to  it.  The 
capsule  had  been  torn  off  with  a  fine  needle.  All  the  above  drawings 
were  made  under  the  microscope. 

The  urine  of  man  is  a  clear,  amber-yellow  liquid,  the  average  specific 
The  urine  its  g^^ty  °f  which  may  be  taken  at  1.020,  giving  an  acid  re- 
properties  and  action  when  first  voided,  but  gradually  becoming  alkaline 
and  turbid.  Its  composition  varies  greatly  with  preceding 
states  of  the  system,  and  the  nature  and  quantity  of  the  food.  It 
amounts,  in  the  course  of  a  day,  to  from  20  to  50  ounces ;  this,  however, 
depending  on  the  quantity  of  water  that  has  been  taken,  and  on  the  ac- 
tivity of  the  skin.  Its  solid  ingredients  vary  from  20  to  70  parts  in  1000 
of  the  urine,  the  leading  substances  being  urea,  uric  acid,  lactic  acid,  ves- 
ical  mucus,  epithelial  debris,  extractive,  and  salts. 

The  urine  of  carnivorous  differs  from  that  of  herbivorous  animals,  the 
latter  being  turbid,  and  having  an  alkaline  reaction ;  that  of  the  former 
transparent,  pale  yellow,  and  acid. 

From  Winter's  experiments,  it  appears  that  for  every  thousand  parts 
of  his  weight  a  man  discharges  25.9  parts  of  urine  per  diem,  the  max- 
imum being  46.8,  the  minimum  14.0.  A  child,  reduced  to  the  same 
standard,  discharges  47.4  parts ;  but  a  cat,  fed  on  a  flesh  diet,  91.036. 
The  quantity  of  water  thus  removed  depends,  to  a  very  great  extent,  on 
the  existing  conditions  of  the  system  ;  sometimes  it  is  far  less  than  would 
answer  to  the  amount  that  has  been  taken ;  sometimes,  on  the  contrary, 
more.  The  solid  material  likewise  exhibits  very  great  fluctuations. 

Viewed  as  a  group,  the  constituents  of  the  urine  are  evidently  the  ox- 
Ori  in  of  the  idized  residues  of  the  system,  which,  unable,  from  their  not 
other  urine  possessing  the  vaporous  or  gaseous  form,  to  escape  through 
constituents.  tjie  lungSj  ^^  from  ti}e^  soiu]bility  in  water,  readily  removed 


COMPOSITION  OF  THE   UKINE.  219 

by  the  kidneys.  The  urea  and  uric  acid  are  derived  from  muscular  de- 
cay;  perhaps,  of -the  two,  the  uric  acid  first  arises,  and  is  subsequently 
converted  into  urea ;  this  is  not,  however,  its  exclusive  source,  since  the 
quantity  of  urea  increases  by  the  use  of  highly  nitrogenized  food.  The 
mucus  and  epithelial  debris  are  derived  from  the  mucous  membrane  lin- 
ing the  interior  of  the  urinary  apparatus.  Of  the  salts,  there  are  two  of 
unusual  interest,  the  sulphates  and  phosphates,  each  having,  like  the 
urea,  a  double  origin,  the  food  and  tissue  decay.  Leaving  out  of  consid- 
eration that  part  which  has  been  supplied  by  the  food,  we  recognize  in 
the  sulphates  the  final  disposal  of  that  sulphur  which  was  once  secreted 
by  the  liver,  and  subsequently  reabsorbed.  In  the  phosphates  we  recog- 
nize the  oxidation  of  the  free  phosphorus  of  the  nervous  Constitution  of 
vesicles  during  their  period  of  activity.  That  portion  of  the  urine- 
solid  constituents  of  the  urine  which  is  due  to  decay  or  retrograde  met- 
amorphosis is  shown  when  an  animal  is  exclusively  fed  on  sugar. 

Composition  of  Urine.     (From  Berzelius.} 

Water 933.00 

Urea 30.10 

Uric  acid 1.00 

Lactic  acid,  lactate  of  ammonia,  and  extractive 1 7. 14 

Mucus 00.32 

Sulphate  of  potash 3.71 

Sulphate  of  soda , 3.16 

Phosphate  of  soda 2.94 

Bi-phosphate  of  ammonia 1.65 

Chloride  of  sodium 4,45 

Muriate  of  ammonia 1.50 

Phosphates  of  lime  and  magnesia 1.00 

Silica 0.03 

1000.00 

The  composition  of  urine  is  not  only  disturbed  by  variations  in  the 
amount  of  its  normal  ingredients,  but  likewise,  in  morbid  states,  by  the 
appearance  of  unusual  ones.  Among  these  may  be  more  particularly 
mentioned  sugar,  albumen,  blood,  bile,  pus,  fat.  The  presence  of  such 
abnormal  ingredients  is  determined  by  chemical  tests  or  microscopic  ob- 
servations. 

Since  the  urinary  apparatus  is  the  sewer  of  the  system,  tables,  like  the 
preceding,  which  purport  to  set  forth  the  composition  of  its  yariability  Of 
excretion,  can  only  be  received  as  general  illustrations.     In  its  constitu- 
the  urine  must  occur  whatever  materials  have  been  gener- 
ated in  the  complicated  disintegration  of  the  economy,  and  whatever  use- 
less substances  have  found  their  way  in  through  the  absorbents  by  rea- 
son of  their  solubility  in  water. 

Eespecting  the  substances  thus  occurring,  either  normally  or  unusu- 
ally, in  the  urine,  the  following  are  observations  of  interest : 

The  quantity  of  urea  excreted  depends  more  upon  the  nature  of  the 


220  OEIGIN   AND   VARIATIONS   OF   UEEA. 

food  than  upon  any  other  condition.     It  reaches  its  maxi- 

Variahons  in  -,11  ,    -,.  -,  . 

the  quantity  mum  under  an  absolute  animal  diet,  and  its  minimum  under 
a  non-nitrogenized  one.  It  still  appears  during  fasting,  and 
about  to  the  same  extent  as  during  a  non-nitrogenized  diet.  Its  sources, 
therefore,  are  partly  the  waste  of  the  tissues  and  partly  the  food. 

By  several  observers,  urea  has  been  detected  in  the  blood  under  ordi- 
nary circumstances.  After  extirpation  of  the  kidneys  it  has  been  re- 
peatedly recognized  in  that  of  the  lower  animals.  It  is  removed  with 
such  rapidity  by  the  kidneys  that  its  quantity  is  probably  never  per- 
mitted to  exceed  a  fiftieth  of  one  per  cent,  of  the  circulating  blood.  Its 
origin  has  generally  been  attributed  to  the  waste  of  muscular  tissue, 
though  it  has  not  yet  been  detected  in  muscle  juice ;  but  then  rt  should 
be  remembered  that  creatine  and  inosic  acid  may  produce  it  during  their 
descending  metamorphosis.  Under  this  view,  the  seat  of  its  production 
would  be  the  blood  itself,  a  conclusion  which  is  enforced  by  the  circum- 
stance that  caffeine  also  increases  its  amount. 

In  his  inaugural  dissertation,  entitled,  "  Is  muscular  Motion  the  Cause 
Origin  of  the  of  the  Production  of  Urea  ?"  Dr.  John  C.  Draper,  by  experi- 
urea.  ments  on  the  urine  of  persons  in  different  conditions  of  motion 

and  rest,  and  by  an  examination  of  the  diurnal  and  nocturnal  variations 
in  the  amount  of  urea  voided,  compared  with  an  invariable  standard, 
gives  reasons  for  concluding  that  the  differences  in  the  amount  of  urea 
excreted  are  almost  entirely  attributable  to  the  influence  of  the  food,  an 
individual  in  such  a  state  of  comparative  rest  as  is  observed  during  treat- 
ment for  a  fractured  leg  not  excreting  by  any  means  so  much  less  urea 
as  might  have  been  anticipated  when  compared  with  another  individual 
who  walked  thirteen  miles  at  the  rate  of  four  and  a  half  miles  an  hour. 

But,  on  examining  the  influence  of  food,  it  appears  to  be  well  marked. 
The  greatest  amount  of  urea  is  excreted  within  a  few  hours  after  dinner. 
Another  maximum  also  occurs  just  after  breakfast ;  but  during  the  eight 
night  hours  far  less  is  excreted  than  during  the  same  period  in  the  aft- 
ernoon. 

The  ingestion  of  food  thus  exercising  so  rapid  and  marked  an  influ- 
ence on  the  quantity  of  urea,  he  refers  to  it  as  the  cause  of  the  increased 
excretion  of  that  substance  during  the  course  of  the  day  rather  than  to 
the  increased  motion  of  exercise  then  indulged  in;  and  in  view  of  this 
conclusion,  it  becomes  probable  that  the  nitrogen  of  the  wasting  muscu- 
lar tissues  escapes,  not  under  the  form  of  urea  through  the  kidneys,  but 
through  the  skin,  or  perhaps  even  as  free  nitrogen  from  the  lungs. 

Of  the  variations  of  the  sulphates,  it  may  be  observed  that  the  aver- 
Variations  of  age  diurnal  excretion  of  sulphuric  acid  per  thousand  parts  of 
the  sulphates.  man  being  0.050  of  a  part,  an  increase  is  observed  during  di- 
gestion, a  diminution  occurring  during  the  night,  the  minimum  being 


EXTKACTIVE  AND   SALTS.  221 

reached  in  the  forenoon.  Exercise  to  a  moderate  degree  does  not  seem 
to  influence  it,  though  that  of  a  more  violent  kind,  and  also  mental  ex- 
citement, do.  Fasting  for  one  day  does  not  diminish  it.  Copious 
drafts  of  water  increase  it,  but  it  subsequently  declines.  The  admin- 
istration of  sulphur,  and  of  the  sulphates  of  potash,  soda,  and  magnesia, 
also  increases  it,  the  latter  salts  being  removed  from  the  system  through 
the  kidneys. 

The  quantity  of  extractive  matter  excreted  by  children  is  much  more 
than  that  excreted  by  adults,  when  estimated,  as  all  such  Quantit  ofex 
observations  ought  to  be,  by  reduction  to  a  common  stand-  tractive  in 
ard.     Thus  Scherer  found  that  for  every  thousand  parts  of  T 
weight  a  child  excreted  0.346  of  a  part  of  extractive  per  diem,  but  an 
adult,  for  each  thousand  parts  of  weight,  excreted  0.156  of  a  part,  which 
is  less  than  half  as  much.   . 

The  quantity  of  chlorine  in  the  urine,  as  chlorides  of  sodium  and  po- 
tassium, undergoes  many  variations.  Hegar  shows  that  it  yariations  in 
is  at  a  maximum  in  the  afternoon,  at  a  minimum  in  the  the  chloride  of 
night,  and  rising  toward  morning.  Its  quantity  is  increased  Sl 
after  taking  water,  and  then  diminishes.  Muscular  exercise  also  in- 
creases it.  It  is  interesting  to  remark  that,  in  inflammatory  conditions 
accompanied  by  copious  exudations,  the  chlorides  in  the  urine  are  so 
much  diminished  that  that  secretion  in  its  fresh  state  will  yield  no  pre- 
cipitate with  nitrate  of  silver.  In  80  cases  of  pneumonia  observed  by 
Kedtenbacher,  the  acidified  urine  did  not  become  turbid  with  nitrate  of 
silver,  but  as  the  inflammatory  action  subsided  the  chlorides  reappeared. 

Of  medicaments  and  other  unusual  substances  introduced  into  the  or- 
ganism, those  which  are  soluble  in  water,  and  have  little  Egca  e  of  unu 
affinity  for  the  constituent  matters  of  the  body,  are  removed  sual  salts  in 
in  the  urine.  In  this  list  are  found  a  great  number  of  salts  t] 
which  escape  in  this  manner  without  undergoing  any  change ;  such,  for 
example,  as  carbonate  of  potash,  nitrate  of  potash,  bromide  of  sodium. 
Other  substances  undergo  change  previously  to  their  elimination,  as,  for 
instance,  the  alkaline  sulphides,  which  become  oxidized,  and  are  then 
finally  removed  as  alkaline  sulphates.  Dr.  Bence  Jones  has  satisfactori- 
ly shown  that,  when  ammonia  is  taken,  it  is  removed  as  nitric  acid  in  the 
urine.  Under  the  administration  of  the  neutral  alkaline  salts  of  vegeta- 
ble acicls,  alkaline  carbonates  in  excess  appear,  owing  to  the  oxidation 
of  their  acid  in  the  blood.  That  this  is  the  true  seat  of  the  oxidation, 
and  that  it  takes  place  with  great  rapidity,  is  demonstrated  by  the  in- 
jection of  such  salts  into  the  jugular  vein,  which  very  soon  are  found  as 
carbonates  in  the  urine. 

When  oxalate  of  lime  is  introduced  into  the  stomach,  it  does  not  make 
its  appearance  in  the  urine,  perhaps  because  of  its  insolubility  present- 


222  HIPPUEIC   ACID,  LACTATES,   PROTEIN   BODIES. 

ing  a  difficulty  to  its  absorption.  In  the  case  of  some  animals  it  occurs 
Production  of  naturally  in  the  excrement.  When,  in  man,  it  is  found  in  the 
dSturbe^re^1  urme»  *ts  occurrence  may  be  often  traced  to  a  disturbance 
piration.  of  the  respiratory  function,  or  to  abnormal  metamorphosis 
occurring  in  the  blood.  Under  such  circumstances  it  presents  itself  in 
convalescence  from  typhus.  That  it  can  arise  from  such  metamorphosis 
is  proved  by  the  circumstance  that  it  is  found  in  the  urine  after  the  in- 
jection of  urates  into  the  veins.  When  the  kidneys  act  vicariously  for 
the  lungs,  there  thus  appears  to  be  a  tendency  to  the  removal  of  carbon 
under  the  form  of  oxalic  instead  of  carbonic  acid. 

Hippuric  acid  may  arise  in  the  organism  from  the  metamorphosis  of 
Occurrence  of  benzoic  and  cinnamic  acids,  the  administration  of  these  sub- 
hippuric  acid,  stances  being  followed  by  its  excretion  in  the  urine.  If  any 
thing  was  necessary  to  prove  that  the  seat  of  its  origin  is  the  blood,  its 
discovery  therein,  in  the  case  of  the  ox,  by  Verdeil  and  Dollfass  would 
be  sufficient.  Its  general  occurrence  in  the  urine  of  graminivorous  ani- 
mals, and  its  absence  in  that  of  the  carnivora,  indicate  that  its  normal 
production  is  connected  with  the  nature  of  the  food.  However,  among 
some  of  the  lower  animals  it  is  still  excreted  while  they  are  in  a  state  of 
starvation,  and  it  has  been  recognized  in  the  urine  of  diabetic  patients 
under  a  strict  animal  diet. 

After  the  injection  of  alkaline  lactates  into  the  jugular,  the  urine  be- 
Disappearance  comes  alkaline  in  the  course  of  a  quarter  of  an  hour.  If 
tates^from  the  tnev  nave  ^een  taken  into  the  stomach,  in  about  double  that 
blood.  time.  The  passage  of  other  salts  is  sometimes  even  more 

rapid ;  thus  the  ferrocyanide  of  potassium  has  been  detected  in  the  urine 
in  less  than  two  minutes. 

The  excess  of  protein  bodies  absorbed  from  the  digestive  canal,  and 
Excess  of  ro-  unnecessary  for  the  repair  of  the  system,  is  removed  as  urea 
tein  bodies  re-  and  uric  acid ;  and,  in  like  manner,  the  sulphur  and  phos- 
phorus introduced  by  those  bodies  are,  after  oxidation,  dis- 
charged as  sulphates  and  phosphates.     Under  the  use  of  a  strictly  ani- 
mal diet,  the  urine  resembles  that  of  carnivorous  animals  in  color,  acid 
reaction,  and  freedom  from  lactic  and  hippuric  acids. 
Disappearance       ^e  Phosphate  of  lime  often  almost  totally  disappears 
of  phosphate  of  during  pregnancy,  and  fractures  unite  at  that  period  with 
difficulty.  -. 

Many  circumstances  regulate  the  length  of  time  that  extraneous  sub- 
Period  that  ex-  stances  will  remain  in  the  system  ;  thus  it  sometimes  occurs 
traneous  sub-  that,  after  the  administration  of  alkaline  salts  of  organic  acids, 
main  in  the  the  alkalinity  of  the  urine  will  disappear  in  the  course  of 
system.  j^f  a  ^av?  whjie  on  Other  occEsions  it  will  continue  for  sev- 

eral days.     The  period  also  varies  very  much  with  different  individuals. 


REMOVAL  OF   URINE   SALTS.  223 

When  the  substance  administered  is  of  such  a  chemical  nature  that  it 
can  unite  with  any  tissue,  it  may  remain  in  the  system  for  a  very  long 
time. 

The  anatomical  construction  of  the  Malpighian  bodies  has  led  physi- 
ologists to  infer  that  there  are  two  distinct  stages  in  the  se-  Manner  of  se- 
cretion of  urine.  These  have  already  been  pointed  out  in  jfiJlto  ij 
the  remark  that  the  Malpighian  bodies  separate  water  from  filtration, 
the  blood,  but  that  the  solid  ingredients  are  secreted  from  that  delicate 
plexus  of  vessels  which  covers  the  walls  of  the  urinary  tubes.  Before 
accepting  this  opinion,  we  may,  however,  observe,  that  the  chief  solid  con- 
stituents of  the  urine,  as  urea,  uric  acid,  sulphates,  and  phosphates,  pre- 
exist in  the  blood,  and  are  all  soluble  in  water.  It  is  not  to  be  supposed 
that  the  water  which  oozes  through  the  delicate  walls  of  the  Malpighian 
tufts  should  leave  such  substances  behind  it.  That  the  loss  of  water 
actually  takes  place  in  the  tuft  circulation  appears  to  be  proved  by  the 
fact  that  the  vessel  emerging  from  the  tuft  is  less  than  the  one  entering 
it ;  the  volume  of  blood  is  less  by  the  amount  of  abstracted  water. 

We  must,  moreover,  take  care  that  we  are  not  deceived  by  a  name. 
The  vessel  emerging  from  the  tufts  may  be  conveniently  ThQ  arterial 
enough  called  a  vein,  but  is  there  any  proof  that  such  is  its  quality  retain- 
physiological  attitude?  '  There  is  no  reason  to  believe  that  ed  in  the  tufts' 
the  blood  has  lost  its  arterial  character  while  it  has  been  in  the  tuft.  At 
the  most,  it  can  only  have  lost  the  elements  of  urine.  It  is  not  until  it 
is  distributed  in  the  plexus  on  the  walls  of  the  uriniferous  tubes  that  it 
really  gains  the  venous  character,  and  then  through  nourishing  those  ves- 
sels, and  particularly  the  cells  of  their  interior. 

These  considerations  therefore  lead  me  to  the  suggestion  that  the  inor- 
ganic bodies,  as  urea,  uric  acid,  sulphates,  and  phosphates,  which  may  all 
be  regarded  as  products  of  final  oxidation,  pass  out  with  the  water  in 
which  they  are  dissolved  while  the  blood  is  yet  circulating  in  the  Mal- 
pighian tuft.  The  loss  of  velocity  in  the  current  by  the  arterial  twig 
breaking  up  into  so  many  vessels  must,  as  Mr.  Bowman  states,  greatly 
favor  this  transudation,  as  does  also  the  pressure  that  must  arise,  from  the 
blood  having  to  pass  through  a  narrow  channel  of  exit,  and  still  more 
through  another  capillary  system  just  beyond.  It  was  arterial  blood  that 
entered  the  tuft,  and  it  is  arterial  blood  that  emerges,  to  be  then  directed 
upon  the  walls  of  the  uriniferous  tubes. 

And  now  the  question  may  arise,  What  is  the  object  of  this  second  cap- 
illary circulation  ?  Though  the  statement  is  often  made  that  The  cells  re- 
the.  constituents  of  the  urine  are  the  results  of  oxidation,  it  ^Jdw^" 
is  very  far  from  being  strictly  true.  The  analysis  of  urine  stances, 
shows  that  a  very  large  proportion  of  them,  classed  as  extractive,  are  real- 
ly combustible  bodies,  and  not  far  advanced  in  their  retrograde  meta- 


224  THE   MAMMARY   GLANDS. 

morphosis.  They  retain  still,  as  it  were,  the  traces  of  organization ; 
they  belong  rather  to  the  hydrocarbon  family  than  to  the  nitrogenized. 
It  may  be  that,  for  the  removal  of  these,  cell  action  is  necessary. 

Whatever  importance  may  be  attached  to  such  a  suggestion,  it  is  very 
Modeofremov-  clear  that,  notwithstanding  the  extreme  thinness  of  the  walls 
from\hVS  of  the  tuft  vessels»  the  relaxation  in  the  speed  of  the  blood 
pighian  sac.  current  through  them,  and  the  pressure  brought  to  bear  upon 
them,  that  water  could  not  be  separated  by  oozing  through  them  unless 
there  was  an  additional  provision.  The  sac  into  which  the  exudation  is 
to  take  place  is  already  full,  and  it  may  be  questioned  whether  ciliary  mo- 
tion in  the  uriniferous  tubes  would  exert  a  sufficient  exhaustion  to  relieve 
the  interior  of  the  capsule  from  pressure ;  but  the  introduction  of  a  liquid 
of  a  different  nature  into  the  uriniferous  tube  may  call  at  once  into  oper- 
ation the  principle  described  at  page  131  as  acting  in  the  capillary  circu- 
lation of  the  blood,  and  thus  the  contents  of  the  Malpighian  sac  are  drawn 
forward  into  the  uriniferous  tube,  just  in  the  same  manner  that  water  is 
drawn  from  the  inside  of  a  bladder  through  the  pores  thereof  by  alcohol 
on  the  outside. 

THE  MAMMARY  GLANDS. 

The  mammary  glands  are  situated  on  various  portions  of  the  abdom- 
„  inal  and  thoracic  surfaces  of  animals  of  the  class  mammalia. 

Description  of 

the  mammary  In  the  higher  members  of  this  class  they  present  the  appear- 
ance of  racemose  glands,  rudimentary  in  the  males,  but  well 
developed  in  the  adult  females,  especially  after  parturition.  They  separ- 
ate from  the  blood  the  white  secretion,  milk. 

In  the  ornithorynchus  the  mammary  gland  consists  of  an  obtuse  cone 
of  coecal  follicles,  ending  upon  an  areolar  surface.  There  is  no  nipple. 
The  milk  is  expelled,  both  in  these  and  the  marsupials,  by  direct  mus- 
cular pressure.  In  cetaceans  the  nipple  is  included  in  a  cleft  of  the  in- 
its  compara-  tegument,  but  in  the  higher  mammalia  it  projects,  so  that,  be- 
tive  anatomy.  'ng  receive<j  in^o  the  mouth  of  the  young,  and  suction  being 
made,  the  pressure  of  the  air  takes  effect  upon  the  surface  of  the  gland 
and  expels  the  milk. 

In  different  cases  the  number  of  mammas  differs.  In  the  human  spe- 
cies there  are  but  two,  placed  upon  the  thoracic  surface,  and  from  their 
position  favoring  the  care  and  nursing  of  the  child.  Among  other  ani- 
mals the  number  seems  to  have  a  relation  to  the  number  of  young  brought 
forth  at  a  birth,  there  usually  being  a  pair  for  each  one.  Many  excep- 
tions to  this  rule,  however,  occur. 

The  mammary  gland  corresponds  in  anatomical  structure  to  the  paro- 

Its  stru      P   t^  anc*  Pancreas-     I*  consists  of  15  or  20  lobes,  each  from  J 

to  1  inch  in  width ;  these  are  composed  of  lobules,  and  these, 

again,  of  coecal  vesicles.     The  excretory  ducts  are  lined  with  tesselated 


STRUCTUEE  OF  MAMMARY   GLAND. 


225 


Fig.  96. 


epithelium.  The  ducts  converge  toward  tKe  nipple,  opening  upon  it  by 
10  or  15  apertures,  and  in  their  course  dilating  into  ampullae,  of  small 
capacity  in  women,  but  in  the  cow  capable  of  holding  a  quart. 

As  regards  its  development,  the  mammary 
gland  originates  in  the  fourth  or  fifth  jts  develop- 
month  as  a  papillary  projection  of  the  ment- 
mucous  layer  of  the  epidermis,  as  shown  in  Fig. 
96,  in  which  1  is  the  rudimentary  gland  in  the 
male  embryo  of  five  months,  a  being  the  horny, 
b,  mucous  layer  of  the  epidermis ;  c,  process  of 
the  latter,  the  rudiment  of  the  gland ;  d,  fibrous 
membrane  round  it.  At  2  is  the  lacteal  gland 
of  a  female  embryo  of  seven  months,  £een  from 
above :  a,  central  substance  of  the  gland ;  b,  <?, 
budding  outgrowths,  the  rudiments  of  the  gland 
lobes.  (Kolliker.) 

Fig.  97,  vertical  section  of  the  human  mam- 
a,  its  pectoral  surface ;  b,  b,  skin  on  surface  of  the  gland ; 
c,  skin  of  nipple ;  d,  lobules  and  lobes  of  gland ;  e,  lac- 
tiferous tubes  passing  from  the  lobules  to  the  nipple. 

As  pregnancy  advances,  the  cells  of  the  gland  begin 
to  contain  fat,  in  a  manner  not  unlike  that  which  is  re- 
marked in  the  cells  of  the  sebaceous  follicles  of  the  skin. 
When  the  gland  becomes  active  after  parturition,  it  is 
stated  that  the  first-formed  milk-cells  break  up  in  the 
lactiferous  ducts  into  milk  globules,  their  membrane  and 
nucleus  disappearing.  The  milk  globules  are  minute 


Development  of  the  mammary 
gland. 


mary  gland 

Fig.  97. 


section  of  the  human 

mammary  gland. 


particles,  varying  in  their  diameter  from  the 


to  the  iSQQQ  of  an  inch.     They  con- 
sist of  oily  material  inclosed  in  an  envelope,  as  is  shown  by  the  fact  that, 
though  they  will  resist  for  a  short  time  the  action  of  sulphuric  ether, 
Fig.  98.  they  are  finally  dissolved  by  that  substance.     Be- 

sides these  milk  globules,  there  are  other  exceed- 
ingly minute  fat  particles  present.  The  milk 
which  is  first  secreted  after  delivery  contains  cor- 
puscles of  considerable  size,  and  of  a  granulated 
appearance,  as  seen  in  the  photograph,  Fig.  98. 
They  are  called  colostrum  corpuscles. 

r™  111-        ,1  i  ^i         f         Colostrum. 

They  are  soluble  in  ether,  and  therefore 
Miik  with  coiostrai  corpuscles.   contain  fat.     There  is  reason  to  suppose  that  all 
the  fat  globules  of  the  milk  are  inclosed  in  cyst-like  pellicles  of  casein. 

In  the  chapter  on  food  (Chapter  II.),  a  general  description  of  the  char- 
acter and  constitution  of  milk  has  been  given,  together  with  its  physio- 

P 


226 


COLOSTRUM   AND   MILK. 


Properties  of  logical  relations  in  nutrition.  It  may  now  be  added  that  fresh 
milk.  milk  presents  an  alkaline  reaction,  which  continues  longer  in 

the  milk  of  women  than  in  that  of  cows.  Left  to  itself,  and  the  more 
quickly  the  warmer  the  air,  milk  turns  sour  through  the  production  of 
lactic  acid,  the  casein  undergoing  coagulation.  That  the  oil  globules  just 
spoken  of  are  coated  with  a  film  of  a  coagulated  protein  body  appears 
from  the  circumstance  that  it  may  be  dissolved  by  acetic  acid,  and  the  in- 
cluded butter  is  then  set  free. 

One  of  the  simplest  methods  for  the  analysis  of  milk  consists  in  coag- 
Anaiysis  of  ulating  it  at  a  temperature  of  212°  with  pulverized  gypsum ; 
milk-  the  mass,  being  then  evaporated  to  dryness,  is  pulverized,  the 
butter  being  extracted  by  ether,  and  the  sugar  and  soluble  salts  by  hot 
alcohol.  *  The  amount  of  the  soluble  salts  thus  obtained  may  be  determ- 
ined by  incineration ;  and  since  their  amount  is  to  that  of  the  insoluble 
salts  as  5  to  7,  an  approximate  determination  of  the  latter  may  be  made, 
and  thereby  the  weight  of  the  sugar  and  casein  corrected.  This  is  the 
method  of  Haidlen. 

It  would  appear,  from  examinations  that  have  been  made  of  the  secre- 
T>  i  *•  f  tion  of  the  mammary  gland  previous  to  parturition,  that  it 
lostrum  and  contains  albumen  in  the  place  of  casein,  the  casein  gradually 
appearing  as  the  period  of  parturition  approaches,  but  not 
reaching  its  maximum  until  a  few  days  after  that  event.  Colostral  milk 
differs  essentially  from  the  subsequent  ordinary  secretion,  as  the  follow- 
ing table  shows : 

Constitution  of  Colostrum  and  Milk.     (From  Simon.') 


Colostrum. 

Milk. 

Water  

828  00 

887  60 

Fat......  

50.00 

25  30 

Casein.  

40  00 

34  30 

70.00 

4820 

Ash  ;  .  . 

3  10 

2  30 

Loss  

8.90 

2.30 

1000.00 

1000.00 

The  specimens  here  presented  were  obtained  from  the  same  individual ; 
and  from  the  table  it  appears  that  the  colostrum  contains  a  much  larger 
proportion  of  solid  material  than  the  milk.  The  quantity  of  fat  is  near- 
ly double  ;  the  quantity  of  sugar  is  likewise  much  greater,  but  the  rela- 
tive quantity  of  casein  is  less,  this  being  in  accordance  with  the  state- 
ment that  the  production  of  that  substance  approaches  gradually  to  a 
maximum  which  is  not  attained  till  a  few  days  after  parturition. 

The  composition  of  milk  varies  with  many  circumstances.  Thus, 
Variability  in  among  cows,  it  is  well  known  that  there  are  certain  breeds 
its  composition.  which  yi^a  a  m$k  {n  wnich  butter  predominates  ;  in  others, 
a  milk  in  which  there  is  an  excess  of  casein.  It  is  in  reference  to  this 
that  such  are,  among  agricultural  people,  often  described  as  good  butter 


VARIATIONS   IN  MILK. 


227 


cows,  or  good  cheese  cows,  as  the  case  may  be.  Such  variations  are 
likewise  often  popularly  referred  to  peculiarities  in  the  color  of  these  ani- 
mals ;  and,  indeed,  there  is  a  general  impression  of  the  same  kind  as  re- 
spects the  milk  of  women,  that  that  of  fair  women  is  inferior  to  that  of 
brunettes.  L'Heritier,  who  has  examined  into  this  matter,  selected  two 
females  of  the  same  age,  22  years,  and  caused  them  to  adopt  the  same 
diet  and  the  same  mode  of  life.  The  one  was  a  blonde,  the  other  a  bru- 
nette. The  following  table  exhibits  the  most  marked  of  his  results  • 

Milk  of  Women  of  different  Temperaments.     (From  UHeritierS) 


The  Blonde. 

The  Brunette. 

"Water       

892.00 

853  30 

Butter                       

35.50 

54  80 

10.00 

16.20 

Sugar  of  xnilk      

58.50 

71.20 

Salts           '               

4.00 

4.50 

1000.00 

1000.00 

The  average  of  the  various  analyses  he  made  shows  the  same  general  re- 
sult, though  not  so  strikingly,  the  number  being  for  the  solid  constitu- 
ents, in  the  case  of  the  blonde,  120,  and  for  that  of  the  brunette,  134. 

As  would  be  expected,  the  constitution  of  the  milk  varies  greatly  with 
the  diet.  Simon  found  that  in  the  case  of  a  very  poor  woman,  influence  of 
who  had  been  almost  deprived  of  the  necessaries  of  life,  the  diet  on  milk- 
quantity  of  solid  material  was  only  8.6  per  cent.  On  giving  her  a  nutri- 
tious meat  diet  it  rose  to  11.9  per  cent.  Being  again  reduced,  by  cir- 
cumstances, to  the  utmost  destitution,  the  solid  residue  sank  to  9.8  per 
cent. ;  and  on  once  more  being  supplied  with  a  nutritious  meat  diet,  the 
percentage  rose  to  12.6.  These  results  illustrate  in  a  striking  manner, 
as  will  be  presently  seen,  the  function  of  the  mammary  gland.  Simon 
also  found,  in  this  particular  case,  that  the  relative  quantities  of  casein 
and  sugar  do  not  greatly  vary  with  these  extreme  dietary  variations,  but 
that  the  absolute  quantity  of  butter  does.  On  the  two  occa-  Qri  in  of  the 
sions  of  starvation,  it  was  as  low  as  8  parts  in  1000  of  milk,  casein  and  of 
and  on  the  two  of  full  nutritious  diet,  it  rose  to  34  and  37  thebutter- 
respectively.  From  this  it  seems  to  follow  that  while  the  amount  of 
butter  in  milk  is  determined  by  the  quantity  and  quality  of  the  food,  the 
amounts  of  casein  and  sugar  are,  to  a  considerable  degree,  independent 
thereof,  and  hence  I  believe  their  origin  is  to  be  attributed  to  changes 
taking  place  in  the  system,  and  that  these  substances  are  more  immedi- 
ately furnished  from  metamorphoses  of  its  structures. 

The  casein  and  the  sugar  are  reciprocally  related  to  each  other,  the 
quantity  of  casein  steadily  increasing  from  the  time  of  par-  Relative  uan 
turition  until  a  fixed  proportion  is  attained.     At  parturition  tity  of  casein 
the  quantity  of  sugar  is  at  its  maximum,  a  gradual  decline  a     sugar' 
then  occurring  until  its  proportion  likewise  becomes  nearly  constant. 


228  ACTION  OF  THE  MAMMARY  GLAND. 

Saline  substances  administered  by  the  stomach  or  rectum  do  not  al- 
Extraneous  ways  appear  in  the  milk ;  thus  the  ferrocyanide  of  potassi- 
saits  in  milk.  unlj  which  may  be  quickly  detected  in  the  urine,  can  not  be 
found  in  the  milk.  It  is  curious,  that  when  iodide  of  potassium  has  been 
administered  to  the  mother,  in  doses,  for  example,  of  three  grains  thrice 
a  day,  it  can  be  readily  detected  in  the  urine  of  the  infant  by  the  usual 
test  of  starch  and  nitric  acid. 

The  diurnal  quantity  of  milk  yielded  by  the  human  female  has  been 
Diurnal  quan-  estimated  at  from  32  to  64  ounces.  This  estimate  is  made 
tity  of  milk,  ^y  determining  the  weight  of  the  infant  before  and  after  suck- 
ling. Although  a  certain  proportion  is  present  in  the  gland,  the  secre- 
tion appears  to  take  place  for  the  most  part  with  great  rapidity.  On  the 
application  of  the  infant  the  blood  flows  suddenly,  and  the  milk  pours 
into  the  ducts,  constituting  what  is  termed  the  draft. 

We  now  enter  on  a  consideration  of  the  function  of  the  mammary 

Mode  of  action  g^an<^»  w^n  a  v^ew  °^  determining  whether  it  acts  in  virtue 

of  the  mamma-  of  its  special  construction,  whether  it  fabricates  in  itself,  by 

the  agency  of  cells,  the  proximate  constituents  of  milk,  or 

whether  it  merely  strains  them  from  the  blood  in  which  they  pre-exist. 

Due  weight  should  here  be  given  to  the  fact  that,  unlike  the  excretions 
of  the  lungs,  the  kidneys,  or  even  the  liver,  the  milk  contains  a  very  large 
percentage  of  histogenetic  or  formative  bodies.  Its  casein  can  not  be 
considered  as  in  the  career  of  retrograde  transformation,  since  in  the  body 
of  the  infant  it  is  presently  changed  into  albumen.  Such  a  fact  might 
even  lead  us  to  suspect  that  we  should  detect  some  essential  structural 
and  functional  differences  between  the  mammas  and  other  glands. 

The  influence  of  special  structure  is,  however,  disposed  of  by  the  nu- 
livfluence  of  merous  well-authenticated  cases  now  on  record,  in  which  por- 
speciai  struc-  tions  of  the  skin,  or  the  stomach,  the  navel,  intestines,  the  ax- 
illa, and  glands  in  the  groin  have  assumed  a  vicarious  action, 
and  secreted  milk ;  and  though  it  has  been  said  of  the  latter  instance  that 
it  may  be  nothing  more  than  an  obscure  manifestation  of  an  attempt  in 
the  human  species  at  a  repetition  of  the  mammary  gland  in  a  region  near 
which  it  is  normally  present  in  the  lower  mammals,  such  a  remark  has 
no  application  in  the  other  cases.  We  may  therefore  infer  that  the  proxi- 
mate constituents  of  the  milk  are  not  manufactured  by  reason  of  any 
special  structure  of  the  gland  which  secretes  them,  since  other  structures 
can  assume  a  vicarious  action. 

This  therefore  narrows  our  inquiry  down  to  the  point,  Does  the  mam- 
mary gland  merely  filter  off  from  the  blood  substances  already  existing 
in  it,  or,  those  substances  not  so  pre-existing,  are  they  made  in  this  or- 
gan by  cells  ? 

Of  the  proximate  elements  of  milk,  many,  such  as  the  entire  group 


SOURCE   OP  THE  BUTTER  OF  MILK.  229 

of  its  salts,  are  acknowledged  on  all  hands  to  pre-exist  in  the  The  galtg  of 
blood ;  and  these,  constituting  about  -^  of  its  solid  ingredi-  milk  exist  in 
ents,  must  be  admitted  to  pass  into  the  secretion  by  strainage 
only.  Of  the  other  solid  ingredients,  the  fat,  which  constitutes  about  one 
fourth,  also  exists  in  the  blood,  being  derived  by  lacteal  absorption  from 
the  food. 

Do  milk-giving  animals,  then,  find  in  their  ordinary  dief  a  sufficient 
quantity  of  oleaginous  material  to  supply  the  drain  establish-  The  hydrocar. 
ed  through  the  mammary  gland,  and  the  calorifacient  de-  bons  pre-exist 
mand,  supposing  none  to  be  made  in  the  system  ?  The  re- 
searches of  Dumas  have  definitely  settled  this  question.  Of  these  the 
following  is  an  abridgment : 

Fat  in  Articles  of  Forage. 

Indian  corn 8.75  per  cent. 

Kice 1.00 

Oats 3.30 

Eye  1.75 

Wheat 2.10 

Dry  hay 2.00 

Clover  in  flower 4.00 

Wheat  straw 3.20 

Oat  straw 5.10 

Beet  root 0.05 

Potatoes 0.08     "      " 

A  cow  in  good  condition,  eating  100  pounds  of  dry  hay,  will  furnish  21 
quarts  of  milk,  from  which  there  can  be  obtained  1J  pounds  Quantity  of  fat 
of  butter.  If  this  butter  was  obtained  exclusively  from  the  in  forase- 
food,  and  none  made  in  the  system,  we  ought  to  find  in  the  100  pounds 
of  dry  hay  1J  pounds  of  fatty  matter;  but  sulphuric  ether  can  remove 
from  such  hay  2  pounds,  and  in  several  specimens  of  clover  cut  in  flow- 
er, M.  Boussingault  found  the  proportion  as  high  as  4  per  cent.  We 
may  therefore  affirm,  relying  on  the  universal  experience  of  farmers,  that 
the  hay  eaten  by  a  milch  cow  contains  more  fat  matter  than  the  milk 
which  she  yields.  Thus  far,  therefore,  we  are  not  authorized  to  regard 
the  animal  as  capable  of  producing  the  butter  found  in  its  milk,  but,  on 
the  contrary,  we  may  be  led  to  suppose  that  the  whole  of  it  is  taken 
from  the  food. 

In  a  physiological  point  of  view,  a  single  experiment  of  this  kind  is 
insufficient.  Errors  may  arise  in  comparing  together  hay  taken  by 
chance,  and  the  produce  of  milk  taken  by  chance.  It  would  doubtless 
be  far  better  to  establish  a  direct  experiment,  giving  the  proportion  of 
butter,  determined  by  analysis,  relatively  to  the  proportion  of  fat  matter 
consumed  by  a  cow.  This  experiment  has  been  made  on  such  a  scale 
and  with  so  much  care  as  to  be  very  convincing.  It  lasted  for  a  year, 
and  was  conducted  on  7  milch  cows,  the  milk,  drawn  twice  a  day,  being 


230  SOUECE   OF   THE   BUTTER   OF   MILK. 

carefully  measured.  The  7  cows  furnished  17,576  quarts  of  milk;  its 
weight  was  36,382  pounds.  Being  analyzed  from  time  to  time,  it  was 
found  to  yield  3.7  per  cent,  of  butter,  completely  deprived  of  water. 
From  this  it  follows  that  these  7  cows  furnished  during  the  year  1346 
pounds  of  butter. 

During  this  time  they  ate  30  pounds  of  hay,  clover,  and  grass  each 
day;  that  is  to  say,  the  7  cows  consumed  during  the  year  77,650  Ibs. 

Now  if  in  100  pounds  of  hay  there  are  1.8  of  fat,  the  77,650  pounds 
represent  1378  ;  recollecting,  however,  the  use  of  clover,  which  is  richer 
in  fat,  the  amount  should  rise  to  more  than  2000  pounds.  But  the  but- 
ter obtained  was  only  1346  pounds. 

From  this  experiment,  therefore,  we  gather,  that  a  cow  which  is  giving 
milk  finds  much  more  fat  in  the  fodder  she  eats  than  is  subsequently 
yielded  in  her  butter.  We  may  therefore  conclude  that  such  an  animal 
extracts  from  her  food  most  of  the  fat  it  contains,  and  that  she  either 
stores  it  up  in  her  adipose  cells,  uses  it  for  the  production  of  heat,  or  con- 
verts it  into  butter. 

In  the  argument,  as  thus  presented  by  M.  Dumas,  the  question  is  con- 
sidered in  its  quantitative  aspect,  no  allowance  being  made,  however,  for 
the  amount  of  oily  material  accompanying  the  fasces,  and  no  estimate  of- 
fered of  the  proportion  destroyed  for  the  sake  of  producing  heat.  It 
might  be  that  the  entire  amount  of  fat  escapes  in  the  former  of  these 
ways,  and  that,  though  a  sufficiency  occurs  in  the  food,  it  is  not  absorbed 
therefrom  into  the  system. 

There  are  many  facts  which  show  that  the  identical  fat  occurring  in 
The  identical  the  food  is  actually  delivered  by  the  mammary  gland  with 
[sfomid^i/the  raany  °f  its  quantities  unchanged.  Thus,  if  by  chance  cows 
milk.  should  eat  the  tender  shoots  of  pine-trees,  or  wild  onions,  or 

other  strong-smelling  herbs,  the  milk  is  at  once  contaminated  with  the 
special  flavor  of  their  oils.  The  same,  too,  takes  place  when  turnips  are 
introduced  in  their  diet.  If  half  the  allowance  of  hay  for  a  cow  is  re- 
placed by  an  equivalent  quantity  of  linseed-cake,  rich  in  oil,  the  cow 
maintains  herself  in  good  condition,  but  the  milk  produces  a  butter  more 
than  usually  soft,  and  tainted  with  a  peculiar  flavor  derived  from  the  lin- 
seed oil. 

To  the  preceding  facts  it  is  unnecessary  to  add  any  observations  in  re- 
lation to  the  carnivorous  mammals,  which  obviously  find  in  their  prey 
large  quantities  of  'fat.  In  the  chapter  on  calorifacient  digestion,  and  in 
that  on  the  functions  of  the  liver,  the  evidence  was  presented  both  as 
regards  the  reception  of  oily  material  from  the  food,  and  likewise  its  fabri- 
Sufficient  cation  in  the  system.  From  these  sources  conjointly  it  may 
of  fat  therefore  be  plainly  seen  that  fats  of  various  kinds  must  al- 


ways exist  in  the  blood.     A  simple  arithmetical  computation, 


CASEIN  FEE-EXISTS  IN   BLOOD.  231 

founded  on  the  data  furnished  by  the  tables  of  the  constitution  of  blood  and 
of  milk  respectively,  will  show  that  there  is  at  any  moment  a  sufficient 
supply  of  fatty  matters  in  the  blood  to  furnish  two  thirds  of  the  diurnal 
amount  of  milk.  It  does  not  seem,  therefore,  philosophical,  under  these 
circumstances,  to  impute  to  the  mammary  gland  a  power  of  forming  but- 
ter. It  doubtless  obtains  that  substance  directly  from  the  blood ;  and  it 
may  be  that  those  bodies  which  are  conceived  of  as  cells,  and  which  are 
supposed  to  arise  in  the  lobules  of  the  gland  in  successive  broods,  which 
run  a  rapid  living  career,  coming  into  existence,  reaching  maturity,  dying 
and  deliquescing  with  incredible  rapidity,  are,  in  reality,  nothing  more 
than  oil  globules  which  have  coated  themselves  over  with  a  cyst  of  coag- 
ulated casein,  as  in  Ascherson's  experiment,  or  just  as  they  become  coat- 
ed with  a  similar  film  immediately  on  passing  from  the  intestine  into  the 
lacteal  vessels  ;  and  this,  accordingly,  is  the  opinion  I  entertain  of  their 
nature. 

Next  of  the  casein.  There  has  been  much  controversy  among  chem- 
ists respecting  the  existence  of  casein  as  a  normal  ingredi-  Reasons  for  in- 
cut in  the  blood.  Theoretically  there  does  not  appear  any  j£SbSl?> 
solid  reason  for  denying  that  it  may  be  one  of  those  constit-  blood, 
uents,  considering  the  analogy  of  constitution  which  it  shows  with  albu- 
men. The  evidence  is  much  more  distinct  and  positive  in  the  case  of 
puerperal  blood,  and  is  greatly  strengthened  by  the  recognized  tendency 
to  the  occurrence  of  kiestine  in  the  urine  during  gestation.  This  sub- 
stance, to  which  much  attention  has  of  late  been  devoted,  makes  its  ap- 
pearance in  such  urine  as  a  pellicle  or  membrane,  which  gradu- 
ally increases  in  thickness.  It  is  not  commonly  seen  before  30 
hours  after  the  urine  is  passed,  nor  later  than  the  eighth  day.  Though 
sometimes  appearing  at  an  earlier  period  of  gestation,  it  is  more  frequent 
in  the  seventh,  eighth,  or  ninth  months.  The  fact  is  not  without  signifi- 
cance for  our  present  purpose,  that  it  may  reappear  in  the  urine  after  par- 
turition if  any  thing  occurs  to  check  the  secretion  of  milk.  Moreover, 
Prout  noticed  it  in  the  urine  of  a  delicate  child  which  was  fed  chiefly  on 
milk.  An  examination  of  it  shows  that  kiestine  is  composed  of  casein,  a 
butyric  fat,  and  the  phosphate  of  magnesia.  Such  a  constitution  betrays 
at  once  its  relation  to  the  secretion  of  the  mammary  gland. 

Lehmann,  who  inclines  to  the  belief  that  kiestine  is  nothing  else  but 
the  formation  of  crystals  of  triple  phosphate  and  fungoid  and  confervoid 
growths,  which  take  place  when  the  urine  becomes  alkaline,  admits  that, 
unless  it  has  been  the  basic  albuminate  of  soda  which  has  been  mistaken 
for  it,  casein  does  occasionally  occur  in  the  urine.  From  the  acknowl- 
edged fact  that  the  acid  interstitial  juice  of  muscle  fibre  contains  casein, 
there  can  not  be  any  doubt,  I  think,  that  that  substance  must  pre-exist 
in  the  blood. 


232  SOUECE  OP  THE  CASEIN  OF  MILK. 

The  occurrence  of  casein  under  the  form  of  kiestine  in  the  urine,  in 
quantity  increasing  as  gestation  advances,  indicates  therefore  that  the 
system  is  assuming  a  propensity  for  the  generation  of  this  substance  from 
its  albumenoid  compounds  ;  and  since,  in  cases  of  starvation,  the  percent- 
age of  casein  in  the  milk  does  not  seem  to  be  materially  affected,  we  are 
to  attribute  its  immediate  source  to  the  system  rather  than  to  the  food. 
In  this  respect  it  differs  from  the  oily  constituent,  butter,  the  percentage 
amount  of  which  is  instantly  affected  by  variations  in  the  nature  and 
quantity  of  the  food.  It  would  seem,  indeed,  that,  from  the  same  plastic 
ingredient,  albumen,  the  soft  tissues  of  both  mother  and  infant  are  fabri- 
cated, with  this  difference,  that  in  the  latter  case  the  temporary  condition 
of  casein  is  intermediately  assumed.  We  have  already  remarked  on  the 
identity  of  constitution  of  albumen,  casein,  and  fibrin,  so  far  as  their  car- 
bon, hydrogen,  nitrogen,  and  oxygen  are  concerned ;  and,  indeed,  these 
compounds  differ  far  less  in  their  physical  characters  from  one  another 
than  albumen  in  its  coagulated  and  uncoagulated  state ;  yet  that  differ- 
ence in  physical  quality  may  be  readily  brought  about  by  so  trifling  an 
agency  as  rise  of  temperature  through  only  a  few  degrees,  and  is  proba- 
bly dependent  upon  the  different  allotropic  forms  which  the  carbon  con- 
stituent is  prone  to  assume.  Giving  due  weight  to  these  various  consid- 
erations, we  shall  find  reason  to  conclude  that  this  constituent  of  the 
milk,  the  casein,  is  directly  derived  from  the  system,  which  can  manufac- 
ture it  at  a  rate  of  about  30  grains  per  hour,  this  being  about  one  half 
the  quantity  of  fibrin  generated  in  the  same  period  of  time  for  the  sup- 
port of  the  muscular  tissues.  Chemically,  the  transition  from  albumen 
to  casein  is  not  to  be  regarded  either  as  an  ascending  or  declining  meta- 
morphosis, but  only  as  the  temporary  assumption  of  a  state  of  passage 
onward  to  the  condition  of  fibrin. 

With  respect  to  the  constitution  of  casein  there  is  considerable  doubt. 
Complex  na-  The  substance  commonly  passing  under  this  title  seems  to 
ture  of  casein.  consist  Of  at  least  two  different  bodies ;  at  all  events,  it  may 
be  separated  into  two  parts,  one  containing  sulphur,  and  the  other  not ; 
moreover,  if  to  milk,  which  has  been  perfectly  freed  from  butter,  there  be 
added  dilute  hydrochloric  acid,  the  ordinary  precipitate  is  yielded,  but 
there  still  remains  in  solution  an  analogous  body,  which  does  not  precipi- 
tate until  the  mixture  is  boiled.  In  milk,  though  much  of  the  casein  is 
held  in  solution,  much  also  exists  in  the  coagulated  state,  forming  the 
wall  of  the  milk  globules.  Its  existence  under  this  membranous  form 
may  be  demonstrated  by  the  action  of  acetic  acid  on  milk  globules  un- 
der the  microscope,  and  also  by  shaking  new  milk  with  ether,  which  pro- 
duces very  little  change ;  whereas,  if  the  milk  were  only  an  emulsion,  the 
ether  should  take  up  the  fat  and  hold  it  in  solution.  Now,  on  the  addi- 
tion of  potash  or  its  carbonate  to  milk  before  the  action  of  ether,  those 


THE  ACTION   OF  THE  MAMMARY  GLAND.  233 

substances  dissolve  the  membrane,  and  then  the  ether  takes  up  the  fat 
and  forms  a  dimly-clear  solution.  We  may  therefore  conclude  that  the 
substance  we  designate  as  casein  consists  of  two  ingredients,  the  protein 
compound,  which  exists  in  a  state  of  solution  in  milk,  and  also  that 
which  forms  the  membrane  of  the  fat  corpuscles. 

Many  of  the  remarks  just  made  respecting  the  origin  of  casein  are  ap- 
plicable to  the  saccharine  constituent  of  the  milk,  the  origin  origin  of  the 
of  which  is  not  to  be  attributed  so  much  to  the  food  directly  sugar  of  milk. 
as  to  the  system ;  for,  in  starvation,  the  sugar,  like  the  casein,  still  con- 
tinues to  form  to  nearly  the  normal  amount.  I  think  it  is  probable  that 
its  production  is  due  to  the  liver,  and  is,  in  reality,  nothing  more  than  an 
indication  of  the  continued  action  of  that  gland,  one  of  the  prime  func- 
tions of  which  is  the  generation  of  saccharine  compounds. 

From  the  data  now  before  us  respecting  the  origin  of  the  different  con- 
stituents of  the  milk,  the  casein,  the  butter,  the  sugar,  and  T'he  mammary 
the  salts,  we  are  able  to  come  to  a  definite  conclusion  re-  gland  acts  by 
garding  the  physiological  action  of  the  mammary  gland.  I 
have  entered  on  this  long  disquisition  from  the  important  bearing  which 
the  decision  we  arrive  at  has  upon  the  whole  theory  of  secretion ;  for  if 
there  be  a  gland  in  the  body  in  which  we  should  expect  to  find  proofs 
of  formative  power,  through  the  agency  of  cell  life  or  otherwise,  in  giving 
rise  to  products  that  did  not  pre-exist  in  the  blood,  it  is  certainly  the 
mammary.  But  now,  as  it  appears  that  all  the  constituents  which  its 
secretion  contains  are  found  in  the  blood,  we  can  scarcely  suppose  that 
the  gland  itself  does  more  than  merely  strain  them  out ;  of  course,  in  com- 
mon with  all  such  structures,  it  possesses  what  might  aptly  be  termed 
an  elective  filtrating  power ;  thus  it  permits  the  exudation  of  the  iodide 
of  potassium  from  the  blood,  but  refuses  a  passage  to  the  ferrocyanide. 
And,  finally,  the  conclusion  to  which,  we  thus  come  recalls  the  remark 
heretofore  made,  that  the  more  thoroughly  we  study  the  secretions  deliv- 
ered by  the  various  glands,  and  the  more  perfectly  we  identify  the  sources 
from  which  their  constituent  ingredients  have  been  derived,  the  more  we 
should  be  disposed  to  impute  glandular  action  to  the  physical  process  of 
elective  filtration,  and  the  less  to  the  agency  of  cell  life. 

OF  THE  SKIN. 

The  skin  is  composed  of  two  layers,  the  epidermis  or  cuticle,  and  the 
derma  or  cutis.  It  contains  tw9  systems  of  glands,  one  for  the  removal 
of  water,  and  another  for  that  of  oily  substances.  It  also  presents  sub- 
sidiary parts  or  appendages,  such  as  the  nails  and  hair. 

The  epidermis,  which  is  the  exterior  portion  of  the  skin,  originates  from 
the  cutis.  It  has  a  different  thickness  in  different  parts;  The  epidermis : 
the  contrast,  in  this  respect,  being  very  well  shown  upon  the  its  structure. 


234  THE   KETE   MUCOSUM  AND   THE   TRUE   SKIN. 

soles  of  the  feet  and  the  eyelids.  In  this  respect  its  use  is  mechanical. 
It  serves  as  a  protective  covering  to  the  parts  it  envelops,  being  thick 
where  pressure  and  hard  usage  have  to  be  provided  for,  and  thinner  where 
there  is  a  necessity  for  motion.  It  consists  of  an  aggregation  of  nucle- 
ated particles  adhering  together,  the  deepest  being  granules,  the  inter- 
mediate more  perfect  cells,  which  gradually  become  flattened  scales  as 
they  are  examined  nearer  the  surface.  They  undergo  constant  exuvia- 
tion, and  are  as  constantly  replaced  from  beneath,  the  superficial  ones 
becoming  dry  and  horny,  thus  furnishing  a  resisting  tegument,  the  oper- 
ation of  which  is  very  well  displayed  by  the  action  of  vesicating  agents : 
a  watery  discharge  from  the  vessels  of  the  cutis  soaks  through  the  lower 
substance  of  the  cuticle,  and  raises  the  dry  layers  above.  The  chemical 
composition  of  these  dry  scales  is  the  same  as  that  of  nail,  hair,  horn, 
and  is  C48,  H39,  N7,  O18. 

At  one  time  it  was  supposed  that  the  rete  mucosum,  or  layer  of  Mal- 
pighi,  which  is  the  lowest  portion  of  the  cuticle,  and  there- 

liete  mucosum   *  o  .... 

and  its  color-  fore  resting  on  the  cutis,  is  a  distinct  structure.  It  is,  how- 
ing  matter.  everj  merely  the  most  recently-formed  portion  of  the  cuticle. 
The  netted  appearance  it  presents  originates  in  the  eminences  of  the  pap- 
illary structure  below.  Many  of  its  constituent  particles  contain  col- 
oring matter,  especially  in  the  dark  races.  The  pigment  seems  to  be 
produced  by  the  agency  of  the  sunlight  and  continued  high  temperature, 
though  it  disappears  gradually  as  the  cells  containing  it  approach  the 
surface.  It  yields  a  very  large  percentage  of  carbon. 

Beneath  the  epidermis  is  the  derma  or  true  skin.  It  is  composed  of 
The  derma  •  ^rous  tissue,  which  also  serves  to  connect  it  with  the  parts 
its  construe-  beneath,  blood-vessels,  lymphatics,  and  nerves.  In  its  areolar 
lon'  tissue  both  the  white  and  yellow  fibrous  elements  are  found, 

the  proportion  of  each  varying  according  to  the  mechanical  function  the 
part  has  to  discharge,  the  yellow  predominating  where  elasticity  is  re- 
quired, and  the  white  where  a  resistance  to  pressure.  The  derma  also 
contains  organic  muscular  fibres,  to  which  its  property  of  corrugation,  as 
in  cutis  anserina,  is  due.  On  different  parts  it  is  of  different  thickness, 
being  thinnest  where  motion  has  to  be  provided  for.  A  deposit  of  fatty 
material,  lodged  beneath,  gives  it  a  yielding  support.  Its  outer  surface 
presents  a  papillary  structure,  which  is  the  instrument  of  touch.  This  is 
more  perfectly  developed  on  the  inner  surface  of  the  palm  of  the  hand  and 
fingers.  The  furrowed  aspect  of  the  cutis  arises  from  this.  A  farther 
consideration  of  the  mechanism  and  functions  of  the  papillge  is  deferred  to 
the  description  of  the  sense  of  touch. 

The  photographic  engraving,  Fig.  99,  represents  a  thin  section  of  the 
epidermis  of  the  foot  of  the  dog. 

The  general  method  of  arrangement  of  the  constituent  portions  of  the 


THE   CUTICLE. 


235 


Fig.  99. 


Fig.  100. 


Perpendicular  section  of  skin  of 

ear,  magnified  10  diameters. 
Epidermis  of  dog,  magnified  20  diameters. 

skin  may  be  gathered  from  the  perpendicular  section  of  that  of  the  ex- 
ternal auditory  meatus  in  Fig.  100.  <z,  the  derma ;  £,  rete  mucosum  ; 
£,  horny  layer  of  epiderma ;  d,  coil  of  ceruminous  glands  ;  6,  their  excre- 
tory ducts ;  y,  their  apertures ;  <?,  hair-sacs ;  A,  sebaceous  glands ;  2, 
masses  of  fat.  (Kolliker.) 

Fig.  101  shows  the  under  surface  of  the  cuticle  detached  by  macera- 
tion from  the  palm,  exhibiting  double  rows  of  depressions,  in  which  the 
papillae  have  been  lodged,  with  the  hard  epithelium  lining  the  sudoripa- 
rous ducts  in  their  course  through  the  cutis.  Some  of  them  are  con- 
torted at  the  end,  where  they  have  entered  the  sweat  gland.  (Todd  and 
Fig.  101.  Bowman.) 

Fig.  102,  papilla?  of  the 
palm,  the  cuticle  being  de- 
tached. (Todd  and  Bow- 
man.) 

Fig.  102. 


Under  surface  of  the  cuticle. 


Papillse  of  palm,  magnified  35 
diameters. 

Fig.  103,  surface  of  the 
skin  of  the  palm,  showing  the 
ridges,  furrows,  cross  grooves, 
and  orifices  of  the  sweat - 
ducts.  The  scaly  texture  of 
the  cuticle  is  indicated  by  the 
irregular  lines  on  the  surface. 
(Todd  and  Bowman.) 


236 


THE   NAILS   AND   HAIE. 


Fig.  103. 


The  nails. 


The  NAILS  constitute  one  of  the  appendages 

of  the  epiderma.     They  are  horny 

coverings  protecting  the  extremities 
of  the  fingers  and  the  toes.  They  originate 
in  a  fold  of  the  cutis,  and  become  free  at  their 
outer  extremity.  The  nail  grows  from  its 
roots,  increasing  in  length,  and  simultaneously 
in  thickness.  Its  rate  of  growth  depends  upon 
the  general  rate  of  nutrition.  During  periods 
of  sickness  or  abstinence,  its  growth  in  both 
directions  is  retarded,  as  is  indicated  by  a  mark 
or  impression  on  its  surface,  and  so  the  nail 
becomes  a  register  of  the  condition  of  nutrition 
during  the  period  of  its  own  existence.  The 

thumb  nail  is  Said  tO  OCCUpy  about  20  Weeks    Skin  of  palm,  magnified  20  diameters. 

in  its  growth  from  the  root  to  the  extremity ;  that  of  the  great  toe  about 
two  years — an  estimate  which  is  probably  too  long. 

THE  HAIE. — Each  hair  originates  in  a  flask-shaped  follicle,  formed  by 
a  depression  of  the  cutis,  and  lined  by  a  continuation  of  the  cu- 
ticle, and,  like  it,  presenting  scales  on  its  superficies  and  round 
cells  beneath.     The  bottom  of  the  follicle  is  the  place  of  origin.     The 
hair  consists  of  two  portions,  the  outer  or  cortical,  and  the  inner  or  me- 
dullary, the  proportions  of  which  differ  very  much  in  different  cases. 
The  surface  of  the  hair  presents  a  layer  of  imbricated  scales,  within  which, 
at  the  lower  part,  are  minute  cells,  but  farther  from  the  root  the  cells  be- 
come larger  and  begin  to  contain  pigment,  the  coloring  matter  being  dis- 
tributed unequally,  sometimes  producing  a  tubular  appearance  in  the  axis. 
The  hair  grows  by  constant  prolongation  from 
the  follicle,  its  color  being  due  to  a  peculiar  col- 
ored oil ;  and  in  the  black  varieties,  iron  predom- 
inates.    The  diameter  of  the  hairs  varies  from 
rh>  to  TsVo  of  an  inch. 

In  Fig.  104,  the  structure  of  the  root  of  a  hair 
and  part  of  its  shaft  is  displayed.  Bulb  of  a 
small  black  hair  from  the  scrotum,  seen  in  sec- 
tion :  # ,  basement  membrane  of  the  follicle ;  &, 
layer  of  epidermic  cells  resting  upon  it,  and  be- 
coming more  scaly  as  they  approach  c,  a  layer  of 
imbricated  cells  forming  the  outer  lamina  or  cor- 
tex of  the  hair :  they  are  more  flattened  and  com- 
pressed the  higher  they  are  traced  on  the  bulb. 
Within  the  cortex  is  the  proper  substance  of  the 
Human  hair  in  section.  hair,  consisting,  at  the  base,  where  it  rests  on 


Fig.  104. 


OF  THE   SUDORIPAROUS  GLANDS. 


237 


Transverse  section  of  human  hair,  magnified 
200  diameters. 


the  basement  membrane,  of  small  angular  cells,  scarcely  larger  than  their 
Fig.  106.  nuclei.     At  d  these  cells  are  more  bulky, 

and  the  bulb  consequently  thicker :  there 
is  also  pigment  developed  in  them ;  above 
d  they  assume  a  decidedly  fibrous  char- 
acter, and  become  condensed ;  0,  a  mass  of 
cells  in  the  axis  of  the  hair,  much  loaded 
with  pigment.  (Todd  and  Bowman.) 

Fig.  105  is  an  engraving  of  a  photo- 
graph of  a  transverse  section  of  human 
hair  from  the  head.  The  outer  line 
shows  the  cortex ;  in  some  the  pigment- 
ary axis  is  seen ;  in  most,  however,  it  is 
absent. 

The  SUDORIPAROUS  GLANDS  originate  in  depressions  of  the  cutis  or 
tissues  beneath,  occurring  in  some  parts,  as  in  the  axilla,  The  SU(ioripa- 
more  numerously  than  in  others.  They  consist  of  a  tube  rous  glands. 
wound  on  itself,  and  sometimes  dividing  in  convoluted*  branches.  The 
knot  thus  arising  is  contained  in  a  cell,  the  wall  of  which  is  copiously 
supplied  with  blood-vessels :  the  duct  passes  through  the  superjacent  tis- 
sues. The  tube  is  formed  of  a  cylinder  of  basement  mem- 
brane lined  with  epithelium.  The  basement  membrane 
may  be  considered  to  be  derived  from  the  outer  surface  of 
the  papillae,  and  the  epithelium  is  an  external  projection  of 
the  cuticle.  The  duct,  on  its  passage  outward,  loses  its 
basement  membrane  as  it  escapes  between  the  papilla; 
and  it  has  a  spiral  or  helical  aspect,  an  arrangement  prob- 
ably intended  to  keep  the  calibre  open.  It  is  estimated 
that  the  number  of  sudoriparous  glands  is  about  seven  mill- 
ions, and  the  total  length  of  their  tubing  about  28  miles. 

Fig.  106  is  a  sudoriparous  gland  from  the  palm  of  the 
hand :  <z,  a,  knot  of  tubes  with  two  excretory  ducts,  b,  b, 
uniting  into  a  helical  canal,  which  perforates  the  epidermis 
at  £,  and  opens  on  its  surface  at  d  :  the  gland  is  imbedded 
in  fat  vesicles  at  e,  e,  e,  e.  (Wagner.) 

The  SEBACEOUS  GLANDS  are  distributed  in  different 
ed2o  giand,  abundance  in  various  parts,  their  office  being  The  sebaceous 

to  lubricate  the  hair,  to  keep  the  skin  in  a  flex-  slands- 
ible  condition,  and  avoid  the  inconveniences  of  friction.  Their  ducts 
open  either  into  the  hair  follicles  or  upon  the  cuticular  surface ;  the  gland 
consisting  of  basement  membrane  lined  with  epithelium,  the  cells  of 
which,  as  they  reach  maturity,  become  filled  with  a  sebaceous  or  oily  ma- 
terial. The  ear  glands  of  this  class  secrete  a  waxy  matter. 


238  OF  THE   SEBACEOUS  GLANDS. 

Such  being  the  construction  of  the  skin,  we  have  next  to  speak  of  its 
action.  It  discharges  a  double  function :  1st,  as  an  excreting,  and,  2d, 
as  an  absorbing  organ.  In  this  respect  it  has  an  analogy  with  the  mu- 
cous membrane,  which,  indeed,  is  a  reflection  or  continuation  of  it. 

Of  the  excreting  action  of  the  skin.  The  skin  permits  water,  saline 
Different  kinds  an^  fatty  substances,  to  escape  from  it  in  quantities  which 
of  perspiration,  differ  on  different  portions  of  its  surface,  the  nature  of  the  se- 
cretions varying  to  meet  local  requirements.  In  the  examination  which 
we  are  now  entering  upon,  we  shall  speak  of  these  substances  and  their 
proportions  in  a  general  way,  overlooking,  for  the  time,  the  particular  va- 
riations. Yet  that  such  variations  exist  is  clear  on  the  most  superficial 
observation.  The  sweat  of  the  feet  differs  from  that  of  the  general  sur- 
face, as,  again,  does  that  of  the  arm-pits. 

It  has  been  usual  to  distinguish  the  watery  transudation  into  two  por- 
Quantityof  tions,  that  which  escapes  from  the  perspiratory  ducts,  and 
water  through  that  passing  through  the  surface  of  the  cuticle.  It  has  even 

the  cuticle  and   ,          r     . ,  J?  -        ,*  i       j    i  .•  e 

from  the  ducts  been  said  that  the  true  glandular  secretion  passing  from  the 
compared.  ducts  is  not  more  than  one  sixth  of  the  total  cutaneous  ex- 
udation ;  but  this,  I  believe,  is  altogether  erroneous.  When  we  recall 
the  impermeable  nature  of  the  horny  and  dried  scales  which  constitute  the 
outer  portion  of  the  cuticle,  and  that  these  are  constantly  coated  over  with 
an  oily  varnish  issuing  from  the  sebaceous  glands,  we  may  infer  that  the 
cutaneous  surface  between  the  mouths  of  the  perspiratory  ducts  is  con- 
structed rather  for  the  hinderance  of  evaporation  than  for  its  promotion ; 
and  though  the  oily  matter  with  which  the  skin  is  thus  imbued  is  justly 
regarded  as  having  for  one  of  its  functions  the  prevention  of  injury  from 
the  admission  of  external  moisture,  it  must  be  equally  effectual  in  stop- 
ping the  escape  of  water  from  within.  The  tardy  manner  in  which  wa- 
ter thus  escapes  is  illustrated  by  the  operation  of  blisters. 

Under  the  form  of  steam,  water  continually  escapes  from  the  skin.  It 
also,  on  certain  occasions,  issues  in  the  liquid  state  as  drops 
and  perspira-  of  sweat.  To  its  escape  under  the  form  of  steam  the  desig- 
nation of  exhalation  or  insensible  perspiration  is  given ;  but  if 
under  the  form  of  sweat,  that  of  sensible  perspiration.  • 

OF  EXHALATION. — On  condensing  the  vapors  which  arise  from  the 
skin,  they  are  found  to  consist  of  water  containing  a  little  acetate  of  am- 
monia. With  the  water  likewise  escapes  carbonic  acid  gas.  With  a 
view  of  ascertaining  the  weight  of  the  matters  thus  lost,  Seguin  inclosed 
Experiments  m'mself  in  an  air-tight  bag,  the  mouth  of  which  was  gummed 
to  ascertain  the  upon  his  face  in  such  a  way  as  to  permit  the  access  of  air  to 
tCT°escapin g™"  tn®  respiratory  organs.  He  then  determined  the  weight  of 
through  the  his  body  and  the  bag  together.  After  several  hours,  on  re- 
weighing,  he  ascertained  the  amount  of  loss  by  pulmonary 


OP  PERSPIRATION.  239 

exhalation.  Then,  taking  off  the  air-tight  bag,  he  was  weighed  again, 
and  after  another  interval  once  more.  The  difference  between  the  two 
last  weighings  is  the  amount  of  the  pulmonary  and  cutaneous  exhalation 
together,  and  from  these  data,  by  a  simple  arithmetical  calculation,  the 
value  of  each  may  be  determined.  By  these  experiments  it  appeared 
that  the  loss  by  pulmonary  and  cutaneous  exhalation  together  is,  on  an 
average,  eighteen  grains  per  minute,  of  which  seven  issue  from  the  lungs 
and  eleven  from  the  skin.  The  variable  action  of  the  skin  is,  however, 
well  illustrated  by  the  extreme  numbers  observed,  the  minimum  being 
eleven  grains,  and  the  maximum  thirty-two.  From  the  experiments  of 
Valentin,  the  average  of  loss  through  the  skin  is  two  pounds  and  nearly 
half  an  ounce  a  day.  Seguin's  experiments  would  make  it  two  pounds 
and  three  quarters.  It  has  been  shown  in  Chapter  X.  that  Causesofthe 
the  action  of  the  skin  is  partly  meteorological :  the  amount  variable  action 
of  water  passing  through  it  depends  on  the  dew-point,  the  ° 
atmospheric  temperature,  the  conductibility  and  perviousness  of  the  cloth- 
ing. Whatever  physical  circumstances  promote  surface  evaporation  cor- 
respondingly promote  the  action  of  the  skin.  Moreover,  this  membrane 
acts  vicariously  with  the  kidneys,  and  this  not  only  as  regards  the  water, 
but  also  as  regards  the  solid  matter,  a  large  amount  of  which  is  thrown 
off  in  the  course  of  the  day. 

In  all  computations  of  the  quantity  of  water  eliminated  by  the  skin, 
it  should  not  be  overlooked  that  any  inclosing  barrier  or  bag  must  neces- 
sarily occasion  a  complete  alteration  in  the  conditions  under  which  the 
action  is  occurring.  On  the  whole,  it  is  perhaps  most  probable  that  the 
ratio  of  the  matters  expired  through  the  skin  and  those  expired  by  the 
lungs  is  as  9  to  5. 

Besides  the  water  secreted  by  the  sudoriparous  glands,  carbonic  acid 
and  nitrogen  escape.  Their  relative  proportion  is  variable,  Transpiration 
and  seems  to  depend,  among  other  things,  upon  the  nature  of  of  gases. 
•  the  food,  the  carbonic  acid  increasing  under  a  vegetable,  and  the  nitrogen 
under  an  animal  diet.  From  the  experiments  of  Dr.  J.  C.  Draper,  above 
referred  to,  it  appears  that  the  absolute  amount  of  these  gases  is  influ- 
enced by  exercise. 

OF  PERSPIRATION. — When  the  atmospheric  temperature  is  high,  and 
more  particularly  if  muscular  exertion  be  resorted  to,  the  ingredients  of 
quantity  of  water  issuing  from  the  perspiratory  ducts  is  so  perspiration, 
great  that  it  can  not  be  evaporated.  It  then  exudes  as  drops  of  sweat, 
which  become  mingled  with  the  oily  secretion  prepared  by  the  sebaceous 
glands.  From  this  commingling  it  is  scarcely  possible  to  obtain  the 
sweat,  in  an  uncontaminated  condition,  suitable  for  analysis,  or  even  to 
exclude  the  detritus  of  the  cuticle  itself.  In  a  thousand  parts  of  sweat 
there  are  from  five  to  twelve  and  a  half  parts  of  solid  material.  Thenard, 


240  EXCRETION   OP   FAT   BY   THE   SKIN. 

by  resorting  to  the  expedient  of  wearing  for  some  days  a  flannel  shirt 
which  had  been  thoroughly  washed  in  distilled  water,  ascertained,  after 
it  had  again  been  washed  in  distilled  water,  that  it  had  become  imbued 
with  the  chloride  of  sodium,  acetic  acid,  phosphate  of  soda,  phosphate  of 
lime,  oxide  of  iron,  and  an  animal  substance.  Berzelius  found  in  the 
sweat  of  the  forehead  chloride  of  sodium,  lactic  acid,  and  muriate  of  am- 
monia. Besides  these,  other  chemists  have  found  butyric  acid,  the  car- 
bonates and  sulphates  of  potash  and  soda,  and  the  carbonate  of  lime. 
That  sweat  contains  sulphur  is  proved  by  keeping  a  portion  of  it :  when 
putrefaction  ensues,  the  sulphide  of  ammonium  is  disengaged. 

Fourcroy  first  detected  urea  in  perspiration,  an  observation  subse- 
quently confirmed  by  Landerer  and  others.  That  the  skin  can,  under 
certain  circumstances,  excrete  urea,  is  proved  by  the  interesting  fact  that 
this  substance  sometimes  occurs  as  a  bluish  powdery  material  on  the 
bodies  of  those  who  have  died  from  cholera. 

In  the  perspiration  formic  acid  also  exists,  and  in  certain  conditions 
Occurrence  of  °^  disease,  as>  f°r  instance,  intermittent,  it  occurs  in  consid- 
formic  acid  in  erable  quantity.  Its  origin  may  be  from  lactic  acid,  which 
perspiration.  passes  through  this  combination  in  gradually  proceeding  to 
its.final  destruction  into  carbonic  acid  and  water.  It  has  been  asserted 
that  the  increased  acidity  of  rheumatic  sweats  is  due  to  a  concentration 
from  evaporation. 

The  sudoriparous  glands  secrete  a  portion  of  fat,  as  is  demonstrated  by 
Experiment  of  the  experiment  of  Krause,  who  removed  from  the  palm  of  the 
Krause.  hand,  on  which  there  are  no  sebaceous  glands,  loose  epithe- 

lial scales  and  fat  by  means  of  ether  and  friction,  and  then  placed  upon  a 
square  inch  of  it  several  thicknesses  of  filtering  .paper,  which  was  kept 
in  contact  for  one  night,  and  properly  protected  externally.  The  paper 
yielded  to  the  action  of  ether  a  fatty  substance,  which  contained  marga- 
rine and  oil,  in  quantity  sufficient  to  make  tissue  paper  translucent. 

But,  besides  the  saline  substances  thus  dissolved  in  water,  the  skin, 
Secretion  of  fat  through  the  action  of  its  sebaceous  glands,  secretes  oleagin- 
and  oil  from  ous  material.  The  nature  of  this  fatty  substance  differs  on 
different  regions,  or  according  to  the  purposes  to  which  it  is 
to  be  applied.  Where  the  ducts  of  the  sebaceous  glands  open  into  the 
hair  follicles,  the  fat  is  of  a  liquid  or  oily  nature.  Sometimes  stearine 
and  margarine,  sometimes  cholesterine  is  set  free.  Before  birth,  this  last 
substance  is  the  chief  constituent  of  the  vernix  caseosa,  coating  the  sur- 
face of  the  skin.  In  this  manner,  sometimes  the  saponifiable  and  some- 
times the  non-saponifiable  fats  or  lipoids  are  used. 

In  the  midst  of  these  complex  actions  a  very  important  principle  may 
Double  action  be  discerned.  I  have  spoken  of  the  double  action  of  the  kid- 
of  the  skin.  nev?  itg  mechanism  for  removing  saline  solutions,  and  also 


ABSORPTION   BY   THE  SKIN.  241 

that  for  combustible  material.  I  have  now  to  present  the  skin  under  the 
same  aspect.  It  is  not  a  mere  analogy  that  exists  between  the  action  of 
these  organs  ;  the  occurrence  of  urea  and  of  the  salt  substances,  the  names 
of  which  have  been  specified  in  both  secretions,  is  a  fact  of  the  utmost  sig- 
nificance. I  believe  that  the  sudoriparous  glands  are  the  counterparts 
of  the  Malpighian  bodies,  and  the  sebaceous  glands,  in  their  function,  are 
the  counterparts  of  the  uriniferous  tubes.  Indeed,  this  double  action  is 
also  distinguished  in  the  case  of  the  mucous  membranes,  which  possess 
one  instrumental  arrangement  for  the  transit  of  saline  solutions,  and  an- 
other for  that  of  fats.  And  since  the  skin,  the  mucous  membrane,  and 
the  great  glands  connected  with  it,  are  all  to  be  regarded  as  developments 
of  one  original  tissue,  we  should  expect  to  discover,  even  in  their  concen- 
tration or  specialization  of  function,  the  traces  of  their  original  and  com- 
mon property.  Development  takes  place  from  the  general  to  the  special ; 
and  hence,  in  parts  which  have  arisen  from  the  same  primordial  structure, 
though  they  may  be  charged  with  the  accomplishment  of  functions  which, 
in  appearance,  differ  essentially,  there  may  be,  both  in  their  action  and 
in  their  construction,  the  traces  of  their  original  identity.  It  is  in  this 
manner  that  the  kidneys,  and  skin,  and  mucous  membrane,  possess  the 
property  of  acting  vicariously  for  one  another.  The  kidney  can  dis- 
charge water  for  the  skin,  or  the  skin  urea  for  the  kidney.  The  com- 
bustible matter,  known  as  extractive  in  the  urine,  can  be  set  free  under 
diminished  renal  action  by  the  sebaceous  glands,  and  the  saline  solutions, 
eliminated  by  the  convoluted  tubing  of  the  tufts  of  Malpighi,  can  be  set 
free  by  the  convoluted  tubing  of  the  sudoriparous  glands.  In  connection 
with  the  views  I  am  here  impressing,  I  would  recall  the  structural  and 
functional  analogy  there  is  between  the  transuding  mechanism  of  the 
kidney  and  the  transuding  mechanism  of  the  skin.  Both  are  arrange- 
ments of  thin  convoluted  tubes,  and  the  same  may  be  remarked  as  re- 
gards the  elimination  of  combustible  material,  which  is  probably  accom- 
plished by  cell  action  in  the  uriniferous  tubes,  and  again  by  cell  action 
in  the  sebaceous  glands. 

Besides  exercising  the  functions  of  exhalation  and  perspiration,  nu- 
merous facts  demonstrate  that  the  skin  exerts  an  absorbent  Absorption  by 
action.  The  endermic  application  of  remedial  agents  estab-  of  g 
lishes  this  in  a  satisfactory  manner.  That  water  can  find  liquids, 
access  in  this  way  is  shown  by  the  assuaging  of  the  thirst  which  may 
occur  on  taking  a  bath ;  nor  is  the  amount  insignificant,  since  it  may 
give  rise  to  a  considerable  increase  of  weight.  Thus  lizards,  which  have 
been  kept  in  a  dry  atmosphere,  and  thereby  suffered  a  diminution,  recov- 
er their  original  weight  after  immersion  in  water ;  nor  is  it  necessary 
that  the  whole  .skin  should  be  brought  into  contact  with  that  liquid ; 
the  same  result  is  obtained  if  merely  the  tail  and  hinder  parts  are  im- 

Q 


242  FUNCTIONS    OF  THE   SKIN. 

mersed.  Gaseous  substances  also  find  entrance  through  the  skin.  If 
the  hand  be  put  into  a  bell-jar  containing  oxygen,  nitrogen,  or  carbonic 
acid  at  the  pneumatic  trough,  absorption  of  those  gases  ensues.  Proba- 
bly it  is  a  standard  function  of  the  skin  to  permit  a  partial  arterialization 
of  the  blood,  atmospheric  oxygen  being  exchanged  for  carbonic  acid 
through  it,  an  action  the  residual  trace  of  the  community  of  function  be- 
tween the  skin  and  mucous  membrane.  In  the  case  of  some  animals 
this  cutaneous  respiration  is  well  marked. 

Kecapitulating  now  the  more  important  actions  of  the  skin,  the  folio w- 
Summarv  of  ™&  statement  raa7  ^e  ma(^e :  ^  regulates,  to  a  certain  extent, 
the  functions  the  amount  of  water  in  the  system,  disposing  of  it,  as  the  case 
of  the  skm.  m^  -^  e^her  ag  sensible  or  insensible  transpiration.  The 
water  doubtless  maintains  its  liquid  condition  until  it  presents  itself  at 
the  mouths  of  the  sudoriparous  ducts,  moistening  the  general  surface  of 
the  skin,  and  then  being  evaporated ;  or,  if  the  supply  be  greater  than 
can  be  thus  removed,  it  accumulates  as  drops  of  sweat.  There  appears 
to  be  no  substantial  reason  for  believing  that  any  portion  of  water  trans- 
udes directly  through  the  structure  of  the  cuticle,  since  the  scales'  which 
compose  it  are  of  an  impervious  and  almost  horny  nature,  and  their  in- 
terspaces are  fortified  against  any  such  leakage  by  the  oily  exudations 
of  the  sebaceous  glands.  With  the  water  thus  presenting  on  the  surface 
are  many  compounds  which  are  also  constituents  of  the  urinary  secre- 
tion. Among  these,  urea  may  be  particularly  pointed  out,  thus  indicating 
a  similarity  of  instrumental  action  between  this  organ  and  the  kidneys, 
and  this  is  farther  substantiated  by  both  containing  provisions  for  the 
elimination  and  escape  of  the  hydrocarbons ;  but  besides  these  direct 
functions  there  are  other  very  important  collateral  agencies  which  the 
skin  exerts,  and  particularly  as  a  regulator  of  temperature.  In  this  re- 
spect the  action  is,  to  a  certain  extent,  meteorological.  But  this  has  been 
previously  treated  of  so  much  in  detail  that  it  is  unnecessary  to  resume 
the  consideration  of  it  now. 


DECAY  AND   NUTRITION.  243 


CHAPTER  XIII. 

OF  DECAY  AND  NUTRITION. 

Of  Decay :  Loss  of  Weight  in  Starvation. — Interstitial  Death. — Effect  of  Allotropism. 

Of  Nutrition :  Nutrition  for  Repair  and  Nutrition  for  Remodeling,  illustrated  in  the  cases  of  Fat 
and  Bone  respectively. 

Of  Fat:  Its  Peculiarities,  modes  of  Occurrence,  and  Origin. — Inquiry  whether  Animals  ever  form 
Fat. — Artificial  Production  of  it. — Animals  both  collect  it  and  make  it. — Accumulation  of  it 
expends  Nitrogenized  Tissue.  —  Conditions  of  the  Fattening  of  Animals.  —  Summary  of  the 
Sources,  Deposit,  and  manner  of  Removal  of  Fat. — Its  partial  Oxidations. — Summary  of  its 
Uses. — Nitrogenized  Nutrition. 

Of  Bone:  The  Skeleton.  —  Structure  and  Chemical  Composition  of  Bone.  —  Sources  of  its  Con- 
stituents.— The  Process  of  Ossification. — Experiments  on  the  Growth  of  Bone. — Influence  of 
Physical  Agents  on  Development  and  Nutrition. 

OF  DECAY. 

THE  animal  mechanism,  as  a  condition  of  its  activity,  is  constantly 
giving  rise  to  wasted  products,  its  parts  in  succession  passing  Retro  rade 
through  retrograde  metamorphosis  or  decay.     From  the  elab-  metamorpho- 
orate  organization  which  they  have  maintained,  they  go  by 
degrees  through  a  descending  course,  which  brings  them  nearer  and 
nearer  to  the  inorganic  state.     Thus  the  fats,  falling  from  one  step  to  an- 
other, finally  emerge  from  the  system  as  -carbonic  acid  and  water,  and 
thus  the  complex  atom  of  protein  degenerates  into  those  substances  and 
ammonia. 

To  this  steady  wasting  away  we  offer  no  resistance.  Having  no  in* 
terior  principle  of  conservation,  the  organism  delivers  itself  LOSS  of  weight 
up  unresistingly,  and,  if  its  necessary  supplies  be  withheld,  in  starvati°n. 
very  soon  succumbs.  The  experiments  of  Chossat  show  that,  taking  the 
mean  of  forty-eight  cases>  including  rabbits,  Guinea-pigs,  turtle-doves, 
pigeons,  hens,  and  crows,  the  body  loses  39.7  per  cent,  of  its  weight  be- 
fore death  by  starvation  ensues ;  that  mammals,  during  the  process  of 
inanition,  lose  daily  4.0  per  cent,  of  their  weight ;  and  birds,  as  indeed 
might  be  expected  from  their  higher  rate  of  respiration,  4.4  per  cent.  It 
follows,  therefore,  that  such  animals,  under  these  circumstances,  lose  one 
twenty-fourth  part  of  their  weight  per  diem  by  destruction  of  tissue,  a 
result  which  corresponds  with  that  of  Schmidt's  experiments,  which  lead 
to  the  inference  that  the  daily  amount  of  properly-selected  food  which  an 
animal  requires  must  amount  at  least  to  one  twenty-third  of  its  bodily 
weight. 

That  the  functional  activity  of  a  part  implies  destruction  is  very  well 


244  INTERSTITIAL   DEATH. 

illustrated  by  the  gradual  waste  of  the  muscles  under  use  ;  that  nervous 
Necessity  of  activity  is  also  dependent  on  oxidation  is  indicated  by  the 
repair.  appearance  of  alkaline  phosphates  in  the  urine.  Generally, 
the  more  active  the  function,  the  shorter  the  life  of  a  part ;  but  even  the 
hair,  the  teeth,  the  cuticle,  the  activity  of  which  is  very  low,  are  no  ex- 
ceptions, for  they,  too,  have  a  limit  of  duration,  and  provisions  for  repair 
or  renewal.  Thus,  as  the  surface  of  the  cuticle  abrades,  it  is  restored  by 
the  development  of  new  cells  below,  and  their  gradual  drying  up  into 
scales ;  and  as  regards  the  teeth,  the  second  set  arise,  as  it  may  be  said, 
from  germs  which  have  been  left  by  the  first,  so  that  when  the  crown  of 
the  deciduous  tooth  dies,  and  its  fang  and  vascular  arrangement  are  ab- 
sorbed, the  new  tooth  is  ready  to  take  its  place. 

Since  it  is  not  merely  superficial  parts,  as  the  hair,  the  teeth,  or  the 
Interstitial  cuticle,  but  also  the  deep-seated  or  interior  ones,  that  undergo 
death.  these  changes,  the  appropriate  designation  of  interstitial  death 
has  been  introduced.  The  removal  of  the  effete  material  is  accomplish- 
ed by  the  aid  of  the  blood,  which  occasions  partial  or  perfect  oxidation, 
with  a  corresponding  liberation  of  heat,  and  then,  dissolving  the  products 
that  have  arisen,  carries  them  away.  We  have  heretofore  discussed  the 
question  how  it  is  that  this  oxidizing  action  of  the  arterial  blood  is  lim- 
ited to  the  dying  parts,  and  how  those  which  are  yet  capable  of  taking  a 
share  in  organization  are  protected.  It  appears  to  me  that  we  are  obliged 
Deca  de  end  *°  admit,  ^n  the  niechanism  of  living  beings,  those  peculiar 
ent  on  aiiotrop-  conditions  which  both  simple  and  compound  bodies  may  as- 
sume, and  which  are  known  as  allotropic  states  in  chemistry. 
The  indifference  to  oxidation  which  carbon,  under  the  form  of  diamond, 
presents,  contrasts  strikingly  with  the  extreme  combustibility  of  lamp- 
black. The  ready  oxidibility  of  phosphorus,  which  causes  the  shining 
from  which  it  has  derived  its  name,  is  no  longer  recognized  in  that  other 
phosphorus  which  has  been  acted  on  by  the  more  refrangible  rays  of  the 
sun.  And  these  are  qualities  which  elementary  atoms  carry  with  them 
when  they  go  into  union  with  other  bodies,  as  is  well  displayed  by  the 
two  distinct  forms  of  phosphureted  hydrogen  gas,  bodies  having  the 
same  composition,  but  the  one  spontaneously  combustible  and  the  other 
not.  Some  reasons  have  also  been  offered  for  imputing  to  the  nervous 
system  a  control  over  these  allotropic  changes,  and  under  this  point  of 
view  we  must  regard  it  as  having,  for  one  of  its  prime  duties,  the  regu- 
lation of  decay.  These  conclusions  receive  weight  from  the  considera- 
tion that  in  plants,  in  the  economy  of  which  no  interstitial  deaths  are 
taking  place,  no  nervous  system  is  found. 


USE,  SOURCE,  AND   DEPOSIT   OF   FAT.  245 

OF  NUTRITION. 

Interstitial  death  and  retrograde  metamorphosis  imply  removal ;  but, 
besides  the  removals  of  wasted  material,  on  account  of  its  in-  Nutrition  for 
ability  to  be  any  longer  subservient  to  the  uses  of  the  econ-  J^mon  ^^u' 
omy,  there  are  also  subordinate  removals,  which  are  con-  modeling. 
nected  with  the  necessary  remodeling  of  parts.  Thus,  during  the  growth 
of  the  skeleton,  bone  earth  is  transferred  from  one  point  to  another,  the 
osseous  cavities  enlarged  or  altered,  and  the  substance  taken  from  them 
is  carried  to  other  points  where  it  is  needed.  Under  such  circumstances, 
the  disappearing  part  is  not,  in  reality,  giving  rise  to  useless  products. 
The  substance  thus  taken  from  the  position  it  occupied  is  as  valuable  as 
it  ever  was,  and  accordingly  it  is  employed  over  again. 

The  restoration  of  material  in  the  place  of  that  which  is  being  con- 
sumed for  use,  and  even  the  preservation  of  excesses  which  may  be  of 
value  at  a  future  time,  is  very  well  illustrated  by  the  deposit  of  fat  in  the 
adipose  tissue.  Transference  from  point  to  point  of  material  which  has 
undergone  no  deterioration  may  be  studied  in  the  history  of  the  growth 
and  development  of  bone.  To  these  cases  in  succession  I  propose  to 
direct  attention. 

First.  Of  the  use,  sources,  and  manner  of  deposit  of  the  fat. 

The  use  of  fat  in  the  animal  economy  doubtless  depends  on  its  heat- 
making  power ;  for,  though  there  are  many  different  varieties  Physiological 
of  this  substance,  solid  and  liquid,  they  are  all  characterized  relations  of  fat. 
by  an  analogy  of  composition,  all  containing  a  great  excess  of  unoxidized 
hydrogen.  It  is,  indeed,  on  this  peculiarity  that  their  employment  in 
domestic  economy  depends.  They  are  all  highly  combustible,  and  evolve 
so  much  heat  as  to  be  very  available  for  the  production  of  flame. 

For  the  better  understanding  of  the  functions  discharged  by  fatty  sub- 
stances, we  may  perhaps  profitably  offer  the  following  statement  of  their 
chemical  relations. 

When  a  fat  or  oil  is  acted  upon  by  an  alkali,  in  contact  with  water  at 
its  boiling-point,  decomposition  ensues,  a  fatty  acid  and  gly-  Chemical 
cerine  being  disengaged,  and  the  acid,  uniting  with  the  alkali,  cuiiarities  of 
gives  origin  to  a  soap.     During  this  action  no  oxygen  is  ab-    at' 
sorbed,  but,  since  the  compounds  arising  present  an  increase  of  weight,  it 
is  evident  that  there  has  been  an  assimilation  of  water.     In  view  of  these 
facts,  it  is  therefore  inferred  that  the  oils  and  fats  are  composed  of  a  fatty 
acid  united  with  the  oxide  of  a  radical,  to  which  the  designation  of  lipyl 
has  been  given,  and  which,  when  it  is  displaced,  combining  with  water, 
gives  origin  to  glycerine. 

Glycerine,  which  is  a  substance  of  considerable  physiological  import- 
ance, is  a  pale  yellow  liquid,  of  a  sweetish  taste,  and  attracting  moisture 


246 


PROPERTIES   OF  FAT. 


from  the  air.  If  fermented  in  a  large  quantity  of  water  with  yeast,  it  is 
converted  into  metacetonic  acid.  It  occurs  in  the  yolk  of  the  egg,  and 
also  in  the  fats  of  the  brain.  By  gradual  oxidation  it  can  give  rise  to 
lactic  acid. 

The  physical  properties  of  the  fats  depend,  for  the  most  part,  on  the 
nature  of  their  acids.  The  fats  derived  from  animals  are  of  various  de- 
grees of  consistency  ;  they  are  colorless  or  white,  lighter  than  water,  bad 
conductors  of  heat.  They  are  insoluble  in  water,  and  burn,  in  the  pres- 
ence of  air,  into  carbonic  acid  and  water,  with  the  evolution  of  much  heat. 
By  the  action  of  certain  nitrogenized  ferments  they  may  be  separated  into 
their  acid  and  glycerine,  and  by  the  action  of  pancreatic  juice,  as  ex- 
plained previously,  may  be  brought  into  the  condition  of  an  emulsion. 
The  more  important  of  the  animal  fats  are  stearine,  margarine,  and  oleine. 
Places  of  occur-  They  are  inclosed  in  cells  accumulated  in  various  parts  of 
rence  of  fat.  the  system,  such  as  in  the  orbit  of  the  eye,  around  the  heart, 
and  among  the  muscles  of  the  face,  under  the  cutis,  and  within  the  bones. 
In  morbid  states  they  sometimes  abound  in  the  kidneys,  liver,  and  spleen. 
They  are  also  discovered  in  some  of  the  animal  fluids  :  thus  they  commu- 
nicate to  the  chyle  its  characteristic  property,  and  therefore  likewise  oc- 
cur in  the  blood.  In  their  relative  amount  they  vary  at  different  periods 
of  life,  being  in  a  larger  proportion  in  childhood,  and  again  after  the  mid- 
dle period.  Their  quantity  likewise  changes  with  physical  changes,  di- 
minishing, for  instance,  after  continued  muscular  exertion,  and  also  by 
long  exposure  to  cold. 

Though  the  amount  of  fat  in  the  blood  varies  with  the  nature  of  the 
Quantity  of  fat  f°od>  it  can  not,  however,  be  increased,  in  a  state  of  health, 
in  the  blood,  beyond  a  certain  point,  owing  to  the  inability  of  the  absorb- 
ents to  receive  more  than  a  definite  quantity.  The  serum  of  arterial  con- 
tains less  fat  than  the  serum  of  venous  blood;  the  blood  of  women  more 
than  that  of  men. 

The  manner  of  occurrence  of  fat  in 

organized  structures  is  twofold  :  oft- 

en it  occurs  in  the  free  state,  but  also 

is  very  commonly  inclosed  in  the  in- 

terior of  cells,  as  shown  in  Fig.  107, 

which  is  a  fat-cell,  a  being  the  adi- 

pose  membrane,  and  b  the  nucleus. 
Fig.  108,  adipose  and  areolar  tissue:   a,  #,  fat- 
cells  ;  &,  &,  fibres  of  areolar  tissue. 

Respecting  the  origin  of  the  fat  substances  in 
Fats  arise  from  plants  there  can  be  no  question.     They 

are  derived  from  the  decomposition  of    AdiP°se  and  areolar  tissue' 


pig.  ios. 


Fat-ceii. 


turning  thereto,  carbonic  acid  and  water  by  those  organisms  under  the  in- 


ARTIFICIAL  FORMATION   OF  FAT.  247 

fluence  of  the  rays  of  the  sun.  It  is  interesting  to  remark  that  to  these 
same  binary  bodies  do  the  fats  return  after  accomplishing  the  successive 
stages  of  their  metamorphosis  in  the  economy  of  animals.  From  car- 
bonic acid  and  water  they  come ;  to  carbonic  acid  and  water  they  return. 

But  the  origin  of  the  fatty  substances  of  animals  is  by  no  means  so 
clear.    One  of  the  questions  which  have  been  debated  in  chem-  ~ 
ical  physiology  is,  Do  animals  collect  from  their  food  all  the  collect  or  fab- 
fat  they  require,  or  have  they  the  power  of  making  it  for  them-  ricate  at- 
selves  ?     In  the  preceding  chapter,  under  the  description  of  the  origin  of 
the  butter  of  milk,  we  have,  in  part,  anticipated  the  facts  which  might 
here  be  presented.     Referring,  therefore,  to  what  has  there  been  said,  it 
will  be  sufficient  now  to  admit  the  general  conclusion  that  fats  and  oils 
very  abundantly  occur  in  plants. 

But  instances  are  not  wanting  which  show  that  from  other  sources 
than  the  vegetable  kingdom,  and  by  processes  very  different  to  those  ex- 
ecuted by  plants,  fats  may  be  made  from  substances  in  which  they  did 
not  pre-exist.  We  select  some  of  these  which  have  been  offered  by  chem- 
ists who  have  asserted  the  power  of  the  animal  system  for  such  a  form- 
ation of  fat. 

1st.  When  an  animal  body  is  buried  under  certain  circumstances,  it 
does  not  undergo  putrefaction,  but  changes  into  a  fatty  or  soapy  gu  oged  Jn 
substance,  adipocire.  Attention  was  first  directed  to  this  fact  stances  of  its 
on  the  occasion  of  exhuming  many  bodies  from  the  cemetery  formatlon- 
of  Innocents  in  Paris.  Those  which  lay  a  certain  depth  beneath  the 
ground  were  found  to  have  undergone  the  change  in  question ;  but  that 
it  does  not  altogether  depend  on  the  condition  of  the  earth  of  the  grave, 
as  respects  moisture  or  other  such  physical  state,  I  have  myself  had  the 
opportunity  of  verifying  in  the  case  of  a  subject  which  had  been  buried 
for  nineteen  years,  and  which  was  disinterred  in  a  condition  of  perfect 
preservation,  so  far  as  exterior  appearance  went,  but  which  had  been 
wholly  converted  into  adipocire.  Yet,  from  the  same  burying-ground, 
many  other  bodies  were  disinterred,  but  none  had  undergone  a  like  change. 

2d.  When  nitric  acid  is  made  to  act  on  fibrin  apparently  deprived  of 
its  fat,  an  oily  substance  is  disengaged. 

3d.  During  the  action  of  nitric  acid  on  starch,  in  the  preparation  of 
oxalic  acid,  a  like  effect  takes  place,  oily  matter  being  set  free. 

4th.  As  has  been  described  in  a  preceding  chapter,  butyric  acid  may  be 
prepared  from  sugar,  through  the  influence  of  casein,  in  the  presence  of 
carbonate  of  lime. 

Though  the  conversion  of  albumenoid  bodies  into  fat  has  not  thus  far 
been  distinctly  accomplished  in  an  artificial  way,  no  doubt  Production  of 
can  exist  that  it  is  possible.     Indeed,  the  experiments  of  fat  from  aibu- 
Quain  and  Virchow  respecting  the  origin  of  adipocire  have  menoid  bodies- 


248  FORMATION   OF   FAT   BY   ANIMALS. 

led  them  to  regard  it  as,  at  all  events  to  some  extent,  arising  from  the 
albuminous  constituents  of  the  muscles  being  decomposed  into  fatty  acids 
and  ammoniacal  salts.  Wagner,  Donders,  Burdach,  and  others,  have  fur- 
nished many  interesting  experiments  on  the  apparent  transmutation  of 
various  bodies,  such  as  pieces  of  coagulated  albumen,  crystalline  lenses, 
etc.,  in  the  abdominal  cavities  of  birds.  These  extraneous  objects  after  a 
time  become  enveloped  in,  and  in  some  cases  permeated  by,  fatty  mate- 
rial. But  that  this  does  not  arise  from  metamorphosis  of  the  protein 
body  introduced  was  well  proved  by  the  last  observer,  who  employed 
pieces  of  wood  and  the  pith  of  elder  with  the  same  result. 

Whatever,  therefore,  may  be  the  conclusion  arrived  at  on  the  cases 
The  carnivora  kere  m*r°duced — whether,  during  a  special  metamorphosis, 
find  fat  in  their  muscular  tissue  can  pass  into  adipocire ;  whether  from  fibrin 
or  starch,  by  the  action  of  nitric  acid,  fats  may  be  made,  or 
whether  these  substances  pre-existed  in  the  material  from  which  they  ap- 
pear to  arise,  and  are  only  disengaged  or  set  free — there  can  be  no  question 
as  regards  one  great  group  of  animals,  the  carnivora,  that  they  find  in  their 
food  a  sufficiency  of  these  hydrocarbons  to  meet  all  their  wants.  It  is 
as  respects  the  other  group,  the  herbivora,  that  this  question  of  the  arti- 
ficial formation  of  fats  from  substances  in  which  they  did  not  pre-exist. 
Do  the  herbiv  an(^  particularly  fr°m  albumenoid  bodies,  becomes  interest- 
ora  ever  make  ing.  Do  the  herbivora  find  in  their  food  all  the  fat  they  re- 
quire, or  are  they  obliged  to  fabricate  a  part  ? 

The  question  whether  there  exists  in  the  animal  mechanism  a  capabil- 
Formation  of  ity  of  forming  fat  from  material  in  which  it  did  not  pre-exist 
fat  by  bees.  may  -foG  considered  as  finally  settled  in  the  affirmative,  after 
much  discussion,  by  the  repetition  of  Gundelach's  experiment  by  Dumas 
and  Milne  Edwards.  This  experiment  consisted  in  the  feeding  of  bees 
with  honey  nearly  free  from  wax,  and  determining  the  quantity  of  fat  in 
their  bodies  at  the  beginning  and  end  of  the  experiment,  and  also  the 
quantity  of  wax  in  the  comb  that  they  made.  The  following  table  gives 
the  result : 

Gramme. 

Fat  found  in  the  body  of  each  bee  at  the  beginning 0.0018 

Wax  each  bee  consumed  with  the  honey,  not  exceeding 0.0003 

Whole  amount  of  fat  derived  from  food 0.0022 

Wax  secreted  by  each  bee 0.0064 

Fat  and  wax  in  the  body  of  each  bee  at  end  of  experiment 0.0042 

From  which  it  appears  that  a  very  large  quantity  of  fat  and  wax  had 
been  produced. 

Admitting  thus  that  the  animal  system  possesses  the  power  of  form- 
The  system  *n&  ^at»  ^  *s  Pr°bable  that,  under  all  circumstances,  it  carries 
continually  forward  that  function,  though  it  may  be  at  different  rates  on 
generates  fat.  c|ifferent  occasions<  guch  a  production  of  fat  probably  com- 


PLANTS   FURNISH   FAT.  249 

mences  in  the  intestinal  tube,  the  material  from  which  it  originates  being 
both  nitrogenized  and  non-nitrogenized.  Thus,  when  ducks  have  been 
fed  on  albumen  containing  but  little  fat,  the  digested  material  in  the  in- 
testine yields  a  larger  proportion  of  fat  than  when  they  have  been  fed  on 
clay,  or  even  on  starch.  If  the  glands  of  the  intestine  secreted  fat  from 
the  blood,  it  would  be  detected  after  feeding  the  birds  with  clay,  and 
hence  we  may  conclude  that  the  source  of  the  increase  observed  is  from 
the  albumen. 

But,  in  addition  to  the  part  they  thus  make,  a  large  portion  of  the  fat 
of  animals  is  undoubtedly  obtained  from  the  food.  This  is  obviously  the 
case  with  carnivora,  and  the  same  may,  indeed,  be  said  of  the  herbivora. 
Very  many  of  the  oleaginous  bodies  have  a  close  chemical  relationship 
to  one  another,  so  that  they  may  be  regarded  as  affording  a  series,  the 
terms  or  members  of  "which  arise  from  successive  partial  oxidations ; 
and  since  the  fats  are  soluble  in  one  another,  they  freely  mix  together, 
and  therefore  many  of  them  may  be  found  co-existing  in  the  adipose  tis- 
sues, some  of  them  less  and  some  of  them  more  advanced  in  their  prog- 
ress of  oxidation.  Whether  they  have  been  derived  from  piants  furnish 
the  food  or  by  indirect  processes  made  in  the  system,  it  is  fatorthemate- 

.     ,      ,    .  ,          -,    .        " .  rials  from 

equally  true  in  both  instances  that  their  primary  source  was  which  it  is 
in  the  vegetable  kingdom.     In  the  former  case  they  occur-  made' 
red  in  the  plant-structure  as  hydrocarbons,  in  the  latter  as  amylaceous 
or  nitrogenized  bodies.     Under  the  influence  of  the  sunlight  the  vegeta- 
ble tissues  obtain  them  by  decomposing  carbonic  acid  and  water,  and  to 
those  two  substances  they  return  after  they  have  undergone  destruction 
in  the  animal  organs,  thus  presenting  a  significant  instance  of  the  alter- 
nate passage  of  atoms  from  the  inorganic  to  the  organic  state,  and  back 
again. 

The  primary  source  of  all  fat  substances  is  therefore  in  plants,  which 
obtain  them  from  the  decomposition  of  the  inorganic  constituents  of  the 
air.  The  excess  of  hydrogen  which  characterizes  this  group  of  bodies  in 
most  instances  is  undoubtedly  derived  from  the  decomposition  of  water, 
and  this  explains  the  fact,  frequently  noticed,  that  the  development  of 
such  hydrocarbons  in  plants  is  often  accompanied  by  the  simultaneous 
appearance  of  acids,  for  the  hydrogen  being  appropriated  by  the  former 
class,  the  residual  oxygen  gives  origin  to  acids  or  is  set  free. 

The  quantity  of  fatty  matter  formed  in  the  ordinary  articles  of  food 
used  by  domestic  animals  seems  to  be  amply  sufficient  to  Quantity  of  fat 
meet  all  their  wants.  If  a  calculation  be  made  of  the  amount 
of  such  materials  consumed  by  cattle  during  the  process  of  mais. 
fattening,  it  will  be  ascertained  that  the  quantity  used  not  only  contains 
sufficient  to  account  for  the  increase  of  weight,  but  also  furnishes  an  am- 
ple supply  for  the  portion  which  is  destroyed  by  respiration.  The  fats 


250  CONDITIONS   OF   FATTENING. 

thus  contained  in  plants  are  often  absorbed  with  but  little  alteration. 
The  fattening  of  cattle  with  linseed-cake  gives  rise  to  an  accumulation 
in  their  adipose  tissues  of  an  oily  material  of  unusual  fluidity,  and  it  is 
a  matter  of  common  observation,  as  previously  mentioned,  that  when 
strong-smelling  oils  have  been  accidentally  used,  their  flavor  will  be  im- 
parted to  the  secretion  of  the  mammary  gland. 

The  quantity  of  fat  in  articles  of  food  is  commonly  estimated  by  the 
solvent  action  of  sulphuric  ether.  It  should,  however,  be  understood 
that  we  can  not  with  correctness  regard  all  the  matters  extracted  by  that 
menstruum  from  plants  as  fat. 

Thus,  either  by  forming  or  by  collecting  from  the  food,  a  supply  of  fat 
The  accumula-  is  obtained,  and  this  is  absorbed  by  the  lacteal  system  in  the 
Uro-16"  manner  already  described.  But  where  fat  is  administered 
tissue,  in  excess,  so  that  large  quantities  of  it  are  retained  in  the 
system,  a  proportionate  cell  formation  arises  for  the  purpose  of  affording 
it  a  receptacle.  The  walls  of  such  cells  are  composed  of  nitrogenized 
material,  and  herein  is  displayed  the  connection  between  the  two  groups 
of  bodies,  the  albumenoid  substance  and  the  fats.  There  is  reason  to 
suppose  that  when,  from  the  food,  a  sufficient  quantity  of  nitrogenized 
material  for  this  purpose  can  not  be  obtained,  resort  is  actually  had  to 
the  muscular  fibre  of  the  system  itself,  but  when  this  also  fails  the  fat 
accumulates  in  the  blood. 

In  the  artificial  fattening  of  animals,  the  indications  to  be  complied 
General  condi-  with  are  very  obvious  :  They  are,  1st.  To  furnish  an  abund- 
fattrni^golan-  ant  ^PP1/  of  oleaginous  material  in  the  food;  2d.  To  pre- 
imais.  vent,  as  far  as  possible,  waste  by  oxidation. 

The  first  indication  is  satisfied  by  the  purposed  employment  of  oleag- 
inous articles,  as,  for  instance,  linseed-cake,  or  by  the  selection,  among 
ordinary  food  substances,  of  those  which,  like  Indian  corn,  abound  in  oil. 
It  is  to  be  remarked  that  the  increase  of  weight  of  an  animal  may  take 
place  in  two  ways :  1st.  By  adding  fat  to  the  deposit  in  the  adipose  tis- 
sues ;  or,  2d.  By  development  of  the  muscles.  It  might  perhaps  be  ad- 
missible to  speak  of  the  former  as  adipose  fattening,  the  latter  as  albu- 
menized.  According  as  it  has  been  subjected  to  one  or  other  of  these 
processes,  an  animal  will  be  very  differently  prepared  for  undergoing  se- 
vere exercise.  A  horse  fed  with  Indian  corn  can  not,  under  those  cir- 
cumstances, maintain  himself  as  well  as  if  he  had  been  fed  on  oats.  In 
the  former  case  his  adipose  tissues  have  been  developed,  in  the  latter  his 
muscular. 

The  second  indication  is  met  by  resorting  to  every  expedient  which 
can  restrain  the  action  of  the  respired  oxygen.  A  state  of  perfect  quies- 
cence is  therefore  to  be  observed.  Muscular  movement  of  every  kind  in- 
creases the  activity  of  respiration.  On  the  contrary,  rest  diminishes  it. 


SOURCES,  DEPOSIT,  AND  REMOVAL  OF  FAT.          251 

If,  in  addition  to  this  state  of  quiet  or  rest,  sleep  likewise  be  indulged  in, 
the  object  is  still  more  perfectly  attained ;  and  if  a  high  temperature  be 
resorted  to,  since  this  checks  the  oxidation  needful  for  maintaining  the 
system  at  its  due  temperature,  this  also  diminishes  the  waste  of  the  fat. 

Under  such  circumstances,  where  every  thing  is  done  to  give  a  supply 
of  fat,  and  every  thing  to  prevent  -its  consumption,  it  may  be  caused  to 
accumulate  in  the  tissues  to  an  extraordinary  amount.  But  The  liver  affect 
this  very  soon  interferes  with  the  action  of  the  liver,  one  of  ed  in  that  oper- 
the  functions  of  which  we  have  seen  is  the  preparation  of  fat.  atlon' 
And  it  may  also  be  remarked  that  many  of  the  diseases  of  that  organ, 
especially  those  occurring  in  hot  climates,  meet  their  explanation  on  the 
principles  we  are  here  inculcating,  the  state  of  rest  produced  by  lassitude, 
the  warm  and  therefore  expanded  air  that  is  breathed,  and  the  improper 
resort  to  oleaginous  articles  of  food. 

In  view  of  the  preceding  facts,  it  may  therefore  be  concluded  that  the 
interior  source  from  which  the  adipose  tissues  are  supplied  Summar  of 
is  the  fat  contained  in  the  plasma  of  the  blood,  into  which  it  the  sources, 
has  been  poured  through  the  thoracic  duct,  or  otherwise  ob-  ^^and^an- 
tained  from  the  digestion  of  food  in  the  small  intestine ;  and  ner  of  removal 
since  the  blood-cells  contain  a  higher  percentage  of  oily  ma- 
terial than  the  plasma  (2.2  per  cent,  may  be  extracted  from  them  by  ether, 
either  as  a  phosphorized  fat  or  glycero-phosphoric  acid),  they  constitute 
reservoirs  of  supply  to  meet  the  exigencies  of  the  system,  there  being  a 
necessary  relation  between  the  quantity  they  can  thus  retain  in  store 
and  the  quantity  contemporaneously  existing  in  the  plasma,  a  diminution 
of  which  at  once  establishes  a  drain  upon  the  cells.  Thus  charged  with 
these  hydrocarbons,  the  plasma  passes  wherever  there  are  adipose  cell- 
germs,  furnishing  to  them  the  special  nutriment  they  require  for  their 
development  'into  fat-cells,  the  wall  and  nucleus  of  which  are  derived  from 
the  blood,  or,  as  we  have  mentioned,  in  certain  cases  actually  from  the 
muscular  tissues.  The  amount  of  fat  which  can  thus  be  held  in  reserve 
depends  in  part  on  the  number  of  germs,  in  part  on  the  supply  of  fat 
from  the  digestive  organs,  and  in  part  on  the  supply  of  appropriate  ma- 
terial for  the  walls  and  nuclei. 

When  the  fat  thus  stored  up  is  wanted,  the  cell  wall  in  many  cases 
deliquesces  or  wastes  away,  surrendering  its  contents  back  to  the  plasma, 
but  probably  much  more  frequently  a  transudation  of  the  hydrocarbon 
takes  place  through  it,  analogous  to  what  has  been  described  as  occur- 
ring in  the  blood-cells  themselves.  This  demand  upon  the  adipose  tis- 
sues may  originate  for  many  reasons,  since  there  may  be  a  necessity  for 
fat  in  the  accomplishment  of  the  various  histogenetic  operations  going 
forward,  or  for  those  of  retrograde  metamorphosis,  or  for  the  maintenance 
of  a  normal  state  of  the  blood  as  respects  its  oleaginous  ingredient,  or  for 


252  USES   OF   FAT. 

the  production  of  heat  by  immediate  and  final  oxidation  into  carbonic 
acid  and  water. 

It  is  not  to  be  supposed,  however,  that  this  final  oxidation  into  car- 
Fats  undergo  bonic  acid  and  water  always  takes  place  at  once  or  abrupt- 
^nslVthe a"  ly*  Every  thing  shows  that  fats  pass  through  successive 
system.  gradations  of  retrograde  metamorphosis,  perhaps  gradually 

losing  by  oxidation  two  atoms  of  carbon  and  hydrogen ;  and,  indeed, 
there  is  reason  to  believe  that,  on  special  occasions,  the  opposite  changes 
happen.  Thus  stearic  acid  may  arise  from  margaric  acid  by  deoxidation. 
It  does  not  occur  to  any  considerable  extent  in  vegetable  food,  having 
thus  far  been  only  found  in  cacao  butter. 

In  a  summary  of  the  uses  of  fatty  substances  may  be  mentioned  the 
Summary  of  production  of  a  high  temperature  by  oxidation ;  their  agency 
the  uses  of  fat.  jn  metamorphosis,  as  displayed  by  the  assistance  they  lend 
in  gastric  digestion;  the  function  they  seem  to  discharge  in  cell  life, 
which  would  appear  to  be  important  if  it  be  true  that  the  nuclei  of  some 
cells  are  composed  of  fat ;  their  relation  in  the  formation  of  bile,  and  their 
probable  connection  with  the  production  of  haematin.  Among,  their  phys- 
ical uses  may  be  mentioned  the  equable  manner  in  which  they  propagate 
pressures  in  all  directions  when  they  are  in  the  liquid  state,  as  is  often 
the  case ;  the  manner  in  which  they  fill  up  vacuities,  and  communicate  a 
roundness  and  solidity  to  the  system ;  their  low  conducting  power  as 
respects  heat,  which  enables  them  to  economize  the  warmth  of  the  body ; 
their  diminishing  of  friction  among  moving  parts,  as  in  the  case  of  the 
muscles ;  and  that  they  discharge  some  highly  important  function  as 
respects  the  nervous  system  is  proved  by  the  manner  in  which  they 
uniformly  occur  in  tubular  nervous  tissue.  In  the  general  metamorph- 
oses of  the  system  they  seem  to  take  an  important  part.  This  may 
be  inferred  from  the  fact  of  their  presence  wherever  cells  •  or  fibres  are 
forming. 

From  what  has  been  said  respecting  the  connection  of  the  fats  with 
the  metamorphoses  of  the  system,  it  is  obviously  incorrect  to  regard  them 
as  constituting  a  purely  respiratory  element. 

Conclusions  similar  to  those  which  have  been  stated  respecting  the 
Nutrition  of  vegeta^e  source  of  the  fats  might  also  be  arrived  at  as  re- 
the  nitrogen-  gards  the  source  of  the  nitrogenized  constituents  of  the  sys- 
tem. These  likewise  are  found  in  plants ;  and  thus,  therefore, 
though  the  carnivorous  animal  may  be  said  to  be  nourished  by  the  car- 
cass on  which  it  feeds,  it  is  nevertheless  strictly  true  that  its  nutrient 
material  is  all  from  the  vegetable  world. 

The  repair  of  muscles,  of  nerves,  of  the  skin,  or  other  such  highly  or- 
ganized parts,  is  dependent  on  the  agency  of  cells.  Since  these  are  un- 
distinguishable,  or  to  all  appearance  perfectly  alike,  it  becomes  a  matter 


STEUCTUEE   OF   BONE.  253 

of  curious  inquiry  how  they  should  be  able  to  occupy  exactly  the  places 
and  discharge  with  precision  the  functions  of  those  which  they  are  re- 
placing? or,  in  the  case  of  growth  and  development,  why  they  should 
combine  so  as  to  take  on  a  determinate,  and,  as  it  were,  predestined  form  ? 
How  is  it  that  such  a  variety  of  structures  spring  up  from  the  same  orig- 
inal cell  ?  How  is  it  that  the  two  halves  of  the  body  have  such  a  sym- 
metrical conformation  in  a  majority  of  instances,  the  one  being  the  exact 
counterpart  of  the  other,  peculiarities  which  are  often  continued  even 
after  the  supervening  of  morbid  conditions,  as  shown  in  such  cases  as 
are  known  by  the  term  of  symmetrical  diseases,  in  which  a  structural 
change  affecting  one  side  of  the  body  affects  also  the  corresponding  part 
of  the  other  side  ?  It  appears  to  me  that  these  and  other  such  instances 
of  nutrition,  growth^  and  development  can  only  be  explained  by  admit- 
ting, as  a  great  and  fundamental  principle  in  physiology,  that  the  primor- 
dial germ  being  in  all  instances  alike,  its  mode  of  development  will  de- 
pend on  the  physical  agents  and  conditions  to  which  it  is  exposed :  a 
principle  which,  though  it  may  seem  of  little  moment  at  the  first  view, 
carries  with  it  consequences  of  the  utmost  importance  at  last. 

Second.  Of  the  structure  and  development  of  bone. 

The  skeleton  in  man  is  composed  of  246  bones,  which  are  usually  di- 
vided into  three  groups,  the  Ions:,  flat,  and  irregular.  Their 

.       &      ,  ,  &  The  skeleton. 

uses  are  purely  mechanical,  such  as  to  give  support  to  the 

soft  parts  ;  to  serve  as  levers  on  which  the  muscles,  by  their  contractions, 

may  act. 

In  structure  bone  offers  an  imperfect  division  into  the  compact  and 
spongy.  '  The  compact  is,  however,  a  porous  mass  full  of  cells  structure  of 
and  passages.  Through  it  there  pass,  more  particularly  in  bone< 
the  longitudinal  direction,  canals  for  containing  blood-vessels  and  nerves : 
they  are  called  haversian  canals.  These,  which  are  well  seen  in  a  thin, 
transverse  section  of  bone  as  irregular  circular  openings,  are  surrounded 
with  lamellae,  and  in  the  basis  substance  occur  hollow  spaces,  the  lacuna?, 
which,  presenting  a  dark  aspect,  were  formerly  mistaken  for  solid  corpus- 
cles ;  they  are,  however,  cavities  from  which  proceed  minute  channels  or 
canaliculi.  In  form  the  lacunas  are  irregularly  oval ;  the  canaliculi  of 
those  nearest  to  the  haversian  canal  communicate  directly  with  its  cav- 
ity, and  there  is  so  complete  an  inosculation  between  adjacent  lacunas, 
by  means  of  these  delicate  tubes,  that  the  whole  so-called  compact  struc- 
ture of  the  bone  may  be  said  to  present  a  connected  system  of  lacunas 
and  canaliculi. 

The  diameter  of  these  delicate  channels  of  intercommunication  is  much 
too  small  to  permit  the  passage  of  blood-cells,  yet  through  them  the 
plasma  readily  finds  its  way  and  thus  carries  forward  the  nutrition  of 
the  entire  bone. 


254  COMPOSITION   OF   BONE. 

Fig.  109  is  a  photograph  of  a  transverse  section  of  part  of  human  fe- 
mur, showing  the  haversian  canals  surrounded  by  their  concentric  lamel- 
la, lacuna,  and  canaliculi.  The  complete  perviousness  of  the  structure 
is  demonstrated. 

Fig.  109.  Fig.  110. 


Transverse  section  of  bone,  magnified  50  diameters.  Lacunae  and  canaliculi  from  frontal  bone. 

Fig.  110,  lacunae  and  canaliculi  of  human  frontal  bone. 

In  chemical  constitution,  bone  may  be  considered  to  be  composed  of 
Chemical  com-  two  Porti°ns>  organic  and  mineral :  the  former  is  gluten,  and 
position  of  in  the  latter  phosphate  of  lime  greatly  predominates,  as  the 
)ne>  following  analysis  by  Berzelius  shows  : 

Analysis  of  Bone.     (Berzelius.) 

Cartilage  (or  gluten) 32.17 

Blood-vessels 1.13 

Phosphate  of  lime .51.04 

Carbonate  of  lime 11.30 

Fluoride  of  calcium 2.00 

Phosphate  of  magnesia 1.16 

Soda,  chloride  of  sodium ...*..... ,. 1.20 

100.00 

An  instructive  separation  of  bone  into  its  leading  constituents  may  be 
Se  aration  of  accomplisned  by  the  action  of  hydrochloric  acid  or  by  cal- 
its  organic  and  cination  respectively.  When  a  bone  is  soaked  in  dilute  hy- 
y  ases.  drochloric  acid  for  a  due  length  of  time,  its  mineral  constitu- 
ent is  removed,  and  the  organic  gluten  is  left  in  the  shape  of  the  original 
bone ;  or,  if  the  bone  be  calcined  in  the  open  fire  with  free  access  of  air, 
the  organic  material  is  consumed  and  the  mineral  material  remains.  A 
more .  critical  examination  shows  that  these  constituents  are  not  merely 
associated  together — they  are,  in  reality,  chemically  combined. 

The  different  degrees  of  softness  and  hardness  which  bones  from  dif- 
ferent animals  present  depend  very  considerably  on  the  amount  of  wa- 
ter they  contain.  The  gluten  is  doubtless,  in  all  instances,  derived  from 


OF   OSSIFICATION.  255 

the  metamorphosis  of  albumenoid  bodies,  a  conclusion  which  Orf  .Q  of  the 
is  well  illustrated  by  what  we  observe  in  the  case  of  the  in-  organic  and 
cubating  egg.     In  the  adult  the  source  of  the  bone-earth  is  earthy  matter- 
twofold :  in  part  it  is  derived  from  the  food,  and  in  part  obtained  from 
the  remodeling  and  changes  of  the  bones  themselves.     In  speaking  of 
the  composition  of  milk,  we  have  already  described  how,  through  the  ca- 
sein of  that  secretion,  a  supply  of  phosphate  of  lime  is  secured  for  in- 
fant life. 

At  its  first  formation,  bone  consists  of  a  gelatinous  material,  which  grad- 
ually becomes  condensed  and  cellular,  presenting  what  is  termed  the  carti- 
laginous state.  In  this  material  vascular  canals  arise,  which,  The  process  of 
concentrating  toward  one  spot,  give  origin  to  the  point  or  ossification, 
centre  of  ossification.  Simultaneously,  the  structure  of  the  cartilage  be- 
comes modified,  its  nucleated  cells  are  elongated,  nucleoli  arising,  and 
smaller  cells  forming.  These  reach  maturity,  and  are  separated  from 
one  another  by  the  material  derived  from  the  deliquescence  of  their  pa- 
rent cells,  which  has  simultaneously  been  taking  place.  The  progress  of 
these  changes  may  be  studied  by  examining  the  calcifying  cartilage  near- 
er and  nearer  to  the  point  of  ossification,  to  which,  as  we  approach,  we 
find  that  the  cells  become  more  and  more  numerous,  a  general  arrange- 
ment into  a  columnar  form  being  now  apparent. 

The  deposit  of  mineral  material  commences  at  the  point  of  ossification, 
and  proceeds  between  the  columnar  arrangement  of  cells,  lateral  branch- 
es between  the  individual  cells  being  successively  given  off,  a  bony  net- 
work thus  arising  which  is  pervious  in  every  part.  In  the  human  em- 
bryo the  cartilaginous  stage  is  completed  in  the  sixth  week,  and  ossifi- 
cation commences  first  in  the  clavicle  during  the  seventh. 

Fig, in,  Fig.  Ill,  perpendicular  section  of  the  ossifying 

border  of  the  shaft  of  the  femur  of  a  child  a  fortnight 
old :  a,  cartilage  in  which  the  cells,  the  nearer  they 
are  to  the  ossifying  border,  are  in  more  extended 
longitudinal  rows;  £,  ossifying  border:  the  dark 
streaks  indicate  the  progressive  ossification  of  the 
intercellular  substance,  the  clear  ones  the  cartilage 
cells,  which  ossify  subsequently;  c,  compact  layer 
of  bone  near  the  ossifying  border ;  d,  the  substantia 
spongiosa  formed  in  the  osseous  substance  by  ab- 
sorption, with  cancelli,  e1  e,  the  contents  of  which  are 
not  shown.  (Kolliker.) 

Fig.  112,  photograph  of  ossifying  cartilage,  the 
dark  portions  showing  the  region  of  complete  ossifi- 

Ossifying  cartilage,  magni-  .mi  i  j.     *  . i.  .L-I 

fied  10  diameters.        cation.     The  columnar  arrangement  of  the  cartilage 
cellssis  very  apparent. 


256 


GROWTH  OF  BONE. 

Fig.  112. 


Fig.  113. 


Ossifying  femur. 


Ossifying  cartilage,  magnified  50  diameters. 

Fig.  113,  femur  of  a  child  a  fortnight  old,  natu- 
ral size :  #,  substantia  compacta  of  the  shaft ;  b, 
medullary  cavity ;  c,  substantia  spongiosa  of  the 
shaft ;  d,  cartilaginous  epiphysis,  with  vascular  ca- 
nals ;  e,  osseous  nucleus  in  the  inferior  epiphysis. 
(Kolliker.) 

When  silver  rings  are  placed  upon  the  shaft  of 
Growth  of  a  growing  bone  at  a  measured  dis- 
siiverrings^nd  tance>  subsequent  examination  shows 
madder.  that  that  distance  still  remains  the 

same,  though  the  bone  may  have  become  much 
longer.  If  such  a  ring  be  permitted  to  remain  a  sufficient  period  of  time, 
it  will  eventually  be  found  in  the  interior  of  the  bone.  When  madder 
is  mixed  with  the  food  of  pigs,  its  coloring  matter  so  unites  with  the 
phosphate  of  lime  of  their  bones  as  to  impart  to  them  a  red  tint.  If  the 
animal  submitted  to  the  experiment  be  very  young,  the  whole  skeleton 
may  be  tinged  in  a  single  day,  a  more  close  examination  showing,  how- 
ever, as  might  be  expected,  that  the  portion  most  completely  acted  upon 
is  that  nearest  to  the  vascular  surface.  In  older  animals  the  coloring 
goes  on  more  slowly ;  the  portion  which  shows  the  effect  most  striking- 
ly is  between  the  shaft  and  extremities,  more  particularly  upon  the  sur- 
face. If  the  madder  be  given,  periodically  and  then  withheld,  alternate 
layers  of  a  red  and  white  appearance  are  produced. 

From  these  experiments,  it  may  be  inferred  that  the  growth  of  a  bone 
Conclusions  is  not  uniform  in  all  parts.  Young  bones  grow  chiefly  toward 
such"  exfperi-  ^e  extremities ;  nor  is  the  growth  cumulative,  the  parts  al- 
ments.  ready  deposited  being  ever  after  preserved ;  for,  if  that  were 

the  case,  it  would  not  be  possible  for  a  ring  placed  in  such  a  manner  as 
has  been  described  to  find  its  way  into  the  medullary  canal.     For  that  to 


OF   NUTRITION.  257 

occur,  there  must  have  been  an  absorption  or  removal  of  the  pre-existing 
parts.  The  tinging  by  madder  shows  that  growth  is  taking  place  wher- 
ever the  plasma  of  the  blood  can  have  access,  and  this  not  alone  upon 
the  proper  vascular  surfaces,  but  also  interstitially. 

It  thus  appears  that  bone,  solid  and  dense  as  it  is,  is  the  seat  of  con- 
tinual changes,  which,  though  they  may  go  on  with  more  activity  in  the 
growing  state,  take  place  also  when  the  structure  has  reached  maturity 
or  apparent  perfection.  From  one  portion  a  part  is  removed,  on  another 
additions  are  made,  the  method  by  which  this  is  accomplished  being 
through  the  access  of  the  blood-plasma,  which  finds  its  way  to  every 
part  by  reason  of  the  pervious  structure  of  the  mass. 

As  to  the  sources  from  which  the  phosphate  of  lime  is  derived,  though 
doubtless  the  food  offers  it  in  considerable  quantity,  there  are  gources  from 
many  reasons  for  inferring  that  the  identical  portion  which  which  material 
has  been  removed  from  one  part  is  used  for  the  extension  1S  denved- 
of  another ;  and  thus  we  may  say  that  there  is  a  plastic  operation  con- 
tinually going  forward,  a  remodeling,  so  as  to  adapt  the  structure  to  its 
new  conditions  if  in  a  growing  animal,  or  to  maintain  it  in  good  repair 
if  in  an  adult. 

Turning  from  the  two  cases  with  which  we  have  been  thus  occupied, 
the  development  and  maintenance  of  the  adipose  and  osseous  tissues,  to 
the  phenomena  of  nutrition  generally,  we  may  conclude  that  there  are 
several  sources  from  which  material  for  these  purposes  may  be  derived  : 
a  part  may  be  obtained  by  absorption  directly  from  the  food ;  a  part  may 
be  manufactured  or  fabricated  in  the  system  itself,  or  may  be  taken  from 
some  locality  therein  in  which  it  has  become  redundant  or  useless,  and 
transferred  elsewhere  to  the  point  at  which  it  is  required. 

The  medium  through  which  these  additions  and  exchanges  for  the  pur- 
pose of  development  or  remodeling  are  accomplished  is  of  course  the 
blood.  It  bears  with  it,  wherever  it  circulates,  the  substances  that  are 
demanded — fibrin  for  muscles,  bone-earth  for  the  skeleton,  fat  for  the  ad- 
ipose tissues. 

It  remains  for  us  to  inquire  into  the  laws  of  deposit  and  development 
involved  in  these  processes,  that  is  to  say,  why,  for  example,  Partg  are  de_ 
is  phosphate  of  lime  laid  down  at  the  points  where  the  phos-  veioped  and 
phate  of  lime  has  been,  or,  if  growth  be  taking  place,  why  Se^fluenL 
are  the  accretions  arranged  in  a  definite  way  both  as  respects  of  physical 
size  and  shape  ?     Upon  this  mquiry  I  do  not  propose  at  pres- 
ent to  enter,  since  it  is  closely  connected  with  the  general  doctrine  of  de- 
velopment, which  will  have  to  be  considered  in  detail  in  the  next  book. 
We  shall  then  find  that  reasons  may  be  assigned  for  the  deposit  of  given 
substances  in  places  that  have  been  vacated  by  others  of  the  same  kind, 
as  in  the  nutrition  of  muscles.     We  shall  also  then  have  to  consider  the 


258  OF  THE   NERVOUS   SYSTEM. 

laws  of  development  from  a  much  more  extensive  point  of  view,  intro- 
ducing the  doctrine  of  the  paramount  influence  of  physical  causes  in  this 
respect,  and  perhaps  we  shall  find  ourselves  brought  to  the  conclusion 
that  the  progressive  career  of  a  cell  is  absolutely  dependent  on  the  phys- 
ical conditions  to  which  it  is  exposed,  and  that  there  is  nothing  extraor- 
dinary in  the  circumstance  that  two  cells  placed  under  conditions  which 
are  alike  will  develop  alike ;  that,  therefore,  a  part  which  is  being  repaired 
will  have  its  additions  made  in  the  same  places,  of  the  same  material,  to 
the  same  extent,  and  of  the  same  form  as  the  part  which  has  been  re- 
moved. 


CHAPTER  XIV. 

OF  THE  NERVOUS  SYSTEM. 

Divisions  of  the  Nervous  System. —  Cerebro-spinal  and  Sympathetic. — Fibrous  and  Vesicular. 

Structure  and  Functions  of  Nerve  Fibres. —  Centripetal  and  Centrifugal. — Rate  of  Conductlbillty. 

Anatomical  Examination  of  the  Structure  and  Functions  of  Nerve  Vesicles. —  They  diffuse  Influ- 
ences, are  Magazines  of  Force. — Element  of  Time  Introduced  by  Registering  Ganglia. —  Oxida- 
tion necessary  to  Nerve  Activity. — Necessity  of  Repair  and  Rest. — Electrical  Examination  of 
the  Functions  of  Vesicles. — Anatomical  and  Electrical  Examinations  agree. 

Automatic  Nerve  Arc. —  Cellated  Nerve  Arc. — Multiple  Arcs. —  Commissures. — Registering  Nerve 
Arcs. — Sensorlum. — Influential  Arc. 

Suggestions  derived  from  cerebral  Structure  respecting  the  Soul. — Its  Independent  Existence  and 
Immortality. 

Ideas  of  Time  and  Space. — Objective,  subjective,  and  Impersonal  Operations. —  Vestiges  of  Im- 
pressions and  their  Interpretation. — Finite  Nature  of  Knowledge. — Mental  Emotions. 

THE  parts  and  functions  which  have  been  thus  far  described  stand  in 
Im  ortanceof  subordination  to  the  important  system  on  the  study  of  which 
the  nervous  we  now  enter.  It  may  be  truly  said  that  the  position  of  any 
animal  in  the  scale  of  life  is  directly  dependent  on  the  de- 
gree of  development  of  its  nervous  system.  Through  this  it  is  brought 
in  relation  with  the  external  world,  deriving  sensations  or  impressions 
therefrom ;  through  this,  also,  all  voluntary  muscular  contraction  takes 
place.  Whatever  the  grade  of  intelligence  may  be,  the  degree  of  devel- 
opment or  expansion  of  the  nervous  system  is  in  close  correspondence 
thereto,  from  the  lowest  conditions  in  which  it  is  first  making  its  appear- 
ance in  tribes  which  are  scarcely  distinguishable  from  vegetable  forms, 
up  to  its  highest  elaboration  in  the  cerebro-spinal  system  of  man. 

The  physiologist  has  to  confess  that  in  this,  which  is,  without  doubt, 
imperfect  con-  ^e  mo^t  important  part  of  his  science,  the  amount  of  what  is 
dition  of  the  known  with  exactness  is  limited :  indeed,  so  great  an  obscu- 
BU  Je°  rity  rests  upon  the  functions  of  the  nervous  system  that  he 

has  to  content  himself  rather  with  the  description  of  structure  than  offer 


DIVISIONS   OF  THE  NERVOUS   SYSTEM.  259 

the  explanation  of  action.  Yet  even  now  a  few  leading  facts  have  been 
determined,  which  foreshadow  the  attitude  in  which  the  whole  subject 
will  stand  when  it  comes  to  be  better  understood.  Among  these  may 
be  numbered  the  localization  of  special  functions  in  special  parts  of  the 
nervous  centres,  as  was  observed  by  Gall ;  the  double  office  of  the  spinal 
nerves,  first  recognized  by  Bell,  that  their  anterior  roots  are  motor  and 
posterior  sensory ;  the  conversion  of  impressions  made  at  the  periphery 
into  motions,  reflex  action,  as  it  has  been  termed,  first  clearly  recognized 
by  Hall ;  the  relation  of  the  ganglia  at  the  base  of  the  brain  to  the  cere- 
brum and  the  spinal  cord,  as  shown  by  Carpenter ;  and  particularly  the 
general  condition  on  which  the  activity  of  the  entire  system  depends, 
that  it  undergoes  oxidation  or  waste,  and,  among  other  products,  gives 
origin  to  salts  of  phosphoric  acid. 

For  the  sake  of  convenience  of  description,  the  nervous  system  is  usu- 
ally regarded  as  consisting  of  two  portions,  the  cerebro-spi-  Division  Of  the 
nal  and  sympathetic.     The  former  is  composed  of  the  spi-  nervous  system 
nal  cord,  the  brain,  the  nerves  proceeding  from  them,  and  Spmai &ri™~ 
their  ganglia;  the  sympathetic  is  composed  of  a  series  of  sympathetic, 
ganglia,  united  by  intercommunicating  threads  on  each  side  of  the  ver- 
tebral column,  and  supplying  branches  to  the  coats  of  the  blood-vessels 
and  viscera  of  the  great  cavities.     Both  portions  contain  two  kinds  of 
structure,  a  fibrous  and  a  vesicular.     The  latter  is  found  in  _.. 

\          f  Fibrous  and 

various  situations  ;  the  former  serves  to  connect  those  mass-  vesicular  stmc- 
es  with  one  another,  or  to  furnish  means  of  communication  *' 
from  point  to  point ;  the  office  of  the  ganglia,  or  nervous  centres,  is  for 
the  reception  of  impressions  and  the  origination  of  motions.  In  the 
brain  the  impressions  of  external  circumstances  are,  as  it  were,  registered, 
and  from  it  originate  the  processes  of  intellection. 

The  study  of  this  portion  of  the  mechanism  of  man  brings  us  therefore 
in  contact  with  metaphysical  science,  and  some  of  its  funda-  Connection  of 
mental  dogmas  we  have  to  consider.  Nearly  all  philoso-  metaphysical 
phers  who  have  cultivated,  in  recent  times,  that  branch  of  phl1 
knowledge,  have  viewed  with  apprehension  the  rapid  advances  of  physi- 
ology, foreseeing  that  it  would  attempt  the  final  solution  of  problems 
which  have  exercised  the  ingenuity  of  the  last  twenty  centuries.  In 
this  they  are  not  mistaken.  Certainly  it  is  desirable  that  some  new 
method  should  be  introduced,  which  may  give  point  and  precision  to 
whatever  metaphysical  truths  exist,  and  enable  us  to  distinguish,  sepa- 
rate, and  dismiss  what  are  only  vain  and  empty  speculations. 

So  far  from  philosophy  being  a  forbidden  domain  to  the  physiologist, 
it  may  be  asserted  that  the  time  has  now  come  when  no  one  is  entitled 
to  express  an  opinion  in  philosophy,  except  he  has  first  studied  physiol- 
ogy. It  has  hitherto  been  to  the  detriment  of  truth  that  these  processes 


260  RELATIONS   OF  PHYSIOLOGY   TO   METAPHYSICS. 

of  positive  investigation  have  been  repudiated.  If  from  the  construction 
of  the  human  brain  we  may  demonstrate  the  existence  of  a  soul,  is  not 
that  a  gain?  for  there  are  many  who  are  open  to  arguments  of  this 
class,  on  whom  speculative  reasoning  or  a  mere  dictum  fall  without  any 
weight.  Why  should  we  cast  aside  the  solid  facts  presented  to  us  by 
material  objects  ?  In  his  communications  throughout  the  universe  with 
us,  God  ever  materializes.  He  equally  speaks  to  us  through  the  thou- 
sands of  graceful  organic  forms  which  are  scattered  in  profusion  over  the 
surface  of  the  earth,  and  through  the  motions  and  appearances  presented 
by  the  celestial  orbs.  Our  noblest  and  clearest  conceptions  of  his  attri- 
butes have  been  obtained  from  these  material  things.  I  am  persuaded 
that  the  only  possible  route  to  truth  in  mental  philosophy  is  through  a 
study  of  the  nervous  mechanism.  The  experience  of  2500  years,  and 
the  writings  of  the  great  metaphysical  intellects,  attest  with  a  melancholy 
emphasis  the  vanity  of  all  other  means. 

Whatever  may  be  said  by  speculative  philosophers  to  the  contrary, 
the  advancement  of  metaphysics  is  through  the  study  of  physiology. 
What  sort  of  a  science  would  optics  have  been  among  men  who  had  pur- 
posely put  out  their  own  eyes  ?  What  would  have  been  the  progress  of 
astronomy  among  those  who  disdained  to  look  at  the  heavens  ?  Yet  that 
is  the  preposterous  course  which  has  been  followed  by  the  so-called  phi- 
losophers. They  have  given  us  imposing  doctrines  of  the  nature  and 
attributes  of  the  mind,  in  absolute  ignorance  of.  its  material  substratum. 
Of  the  great  authors  who  have  thus  succeeded  one  another  in  ephemeral 
celebrity,  how  many  made  themselves  acquainted  with  the  structure  of 
the  human  brain  ?  Doubtless  some  had  been  so  unfortunate  as  never  to 
see  one !  yet  that  wonderful  organ  was  the  basis  of  all  their  speculations. 
In  voluntarily  isolating  themselves  from  every  solid  fact  which  might 
serve  to  be  a  landmark  to  them,  they  may  be  truly  said  to  have  sailed 
upon  a  shoreless  sea  from  which  the  fog  never  lifts.  The  only  fact  which 
they  teach  us  with  certainty  is  that  they  know  nothing  with  certainty. 
It  is  the  inherent  difficulty  of  their  method  that  it  must  lead  to  unsub- 
stantial results.  What  is  not  founded  on  a  material  substratum  is  nec- 
essarily a  castle  in  the  air. 

Returning  now  to  the  general  description  of  the  nervous  mechanism, 
and  following  the  division  above  indicated,  we  shall  consider,  first,  the 
fibrous  element  of  the  nervous  system,  and,  second,  the  vesicular. 

First.  Of  the  fibrous  there  are  two  varieties,  one  belonging  to  the 
Fibrous  or  tu-  cerebro-spinal,  and  the  other  to  the  sympathetic.  The  for- 
buiar  portion.  mer  mav  -foQ  described  as  a  delicate  membranous  tube  contain- 
ing a  semi-fluid  material,  and  presenting  under  the  microscope  a  pellucid 
glassy  appearance  when  examined  in  the  recent  state ;  a  spontaneous 
separation  or  partition,  however,  soon  ensues,  a  white  material  or  medul- 


NERVE   FIBRES   OR  TUBES.  261 

la  appearing  immediately  within  the  membranous  tube,  and  affording  a 
contrast  to  the  portions  which  are  toward  the  centre  or  axis.  In  this 
state  the  nerve-tube  presents  the  appearance  of  parallel  lines  toward  its 
periphery,  the  outer  one  corresponding  to  the  membranous  Membrane, 
sheath,  and  the  inner  to  the  internal  limit  of  the  coagulated  J^£l*tance 
material.  In  this  condition  the  tube  is  very  prone  to  as-  axis  cylinder, 
sume  a  beaded  appearance,  either  by  the  influence  of  pressure,  or  even 
spontaneously.  Names  have  been  given  to  distinguish  these  parts  from 
each  other ;  the  central  grayish  portion  is  called  the  axis  cylinder  or  axis 
band,  since  it  may  be  of  a  flattened  shape ;  and  the  material  which  sur- 
rounds it,  intervening  between  it  and  the  membranous  investment,  is  des- 
ignated the  medulla  or  white  substance  of  Schwann.  There  can  be  no 
doubt  that  the  membranous  tube,  the  white  substance,  and  the  axis  cyl- 
inder discharge  different  physiological  functions.  In  chemical  composi- 
tion they  also  differ :  the  tube  is  a  nitrogenized  structure,  the  white  sub- 
stance oleaginous,  and  the  axis  cylinder  is  supposed  to  be  nitrogenized 
also.  In  the  first  development,  the  axis  cylinder  is  first  formed,  and  the 
white  substance  then  cast  round  if. 

If  a  portion  of  a  nerve,  a,  Fig.  114,  be  placed 
in  concentrated  acetic  acid,  the  axis  cylinders  of 
its  included  tubes  will,  in  the  course  of  a  day 
Axis  cylinder  of  nerveiT  or  ^  ^  geen  protruding  in  a  brush-like  form, 
as  at  £,  the  effect  being  very  well  shown  when  the  nerve  is  sufficiently 
slender  to  be  subsequently  examined  by  the  microscope. 

The  nerve  fibres  run  in  a  direct  course  to  their  point  of  distribution. 
Of  their  manner  of  termination  we  shall  speak  subsequently ;   Terminal 
here,  however,  it  may  be  remarked,  that  occasionally  they  ex-  branchings  of 
hibit  preparatory  terminal  branchings,  as  shown  in  Fig.  115, 
p.  262,  observed  by  Kolliker  in  the  case  of  the  frog :  tf,  a  being  bifurca- 
tions, b  a  trifurcation  of  a  small  twig  from  the  cutaneous  thoracic  muscle. 
Similar  subdivisions  of  the  ultimate  ramifications  have  been  noticed  in  the 
amphioxus,  fishes,  insects,  and  it  is  certain  that  they  also  occur  in  man. 

The  sheath  of  the  nerve  fibres  is  an  elastic  membrane,  which  is  nei- 
ther acted  on  by  dilute  alkalies  nor  by  boiling,  but  is  solu-  Chemical  reac- 
ble  in  concentrated  acetic  acid  and  strong  solutions  of  pot- 
ash  and  soda.  By  nitric  acid  it  is  stained  yellow,  and,  though  fibres, 
not  identical  with  elastic  tissue,  has  a  certain  resemblance  thereto,  ap- 
proaching, however,  more  nearly  to  a  protein  substance.  The  axis  cyl- 
inder is,  as  is  shown  by  its  behavior  with  reagents,  a  protein  substance, 
differing,  however,  from  syntonin  and  also  from  blood  fibrin.  From  the 
latter  substance  it  is  distinguished  both  by  the  difficulty  with  which  it 
dissolves  in  acetic  acid  and  in  a  solution  of  nitre,  from  the  former  by  its 
insolubility  in  hydrochloric  acid. 


262 


NERVE   FIBRES   OR   TUBES. 

.Fig.  115. 


Subdivision  of  nerve  fibres  in  the  frog,  magnified  350  diameters. 

Of  such  fibres,  arranged  parallel  to  each  other  in  bundles,  the  bundles 
united  by  fibro-cellular  tissue,  nerves  are  composed,  the  tissue  not  only 
accomplishing  that  mechanical  object,  but  also  affording  a  nidus  for  blood- 
vessels, which  run  in  a  course  parallel  to  the  nerve  fibres.  Though  we 
Form  and  size  have  spoken  of  those  fibres  as  cylinders,  they,  in  reality,  ap- 
of  nerve  fibres,  proach  more  nearly  to  the  figure  of  acute  cones,  since,  though 


their  diameter  is  from  the   2^0  o" 


Wo 


an 


*n 


nerve 


trunks,  they  diminish  to  the  10^QO  or  the  T4^OQ  of  an  inch  as  they  reach 
the  nerve  centres,  and,  in  the  same  manner,  their  diameter  becomes  less 
as  they  branch  off  in  their  peripheral  distribution.  In  the  brain,  as  they 
pass  through  the  medulla  to  the  cortical  part,  they  exhibit  a  similar  dim- 
inution. 

The  sympathetic  fibres  differ  from  the  preceding  in  appearance.  Being 
Character  of  °^  a  yeU°wish-gray  color,  and  only  about  half  as  large,  they 
sympathetic  do  not  show  the  separation  into  an  axis  cylinder  and  white 
investment  after  death,  as  is  the  case  with  cerebro-  spinal 
fibres  ;  they  may  therefore  be  regarded  as  being  more  homogeneous  in 
their  construction,  or  possessing  a  constitution  like  that  of  the  other  kind 
of  fibres  when  they  undergo  diminution  and  approach  their  central  or 
peripheral  termination.  Even  in  the  cerebro-spinal  fibres  the  quantity 
of  white  substance  present  is  very  variable  ;  the  retina,  the  olfactory  or- 
gan, and  the  Pacinian  corpuscles  furnish  instances  of  its  absence.  The 
sympathetic,  gray,  or  gelatinous  fibres,  as  they  are  indifferently  called, 
contain  many  nucleated  corpuscles,  which  may  be  rendered  very  distinct 
by  the  action  of  acetic  acid. 


NERVE   VESICLES.  263 

Nerve  fibres  terminate  in  various  ways.     Their  ends  may  tliin  out  and 
become  free,  or  they  may  form  a  loop,  and  so  return  back  in  Manner  of 
their  course.     Each  nerve  runs  in  an  unbroken  line  from  its  termination  of 
origin  to  its  termination,  but  between  the  adjacent  ones  in- 
tercommunication is  established  by  the  formation  of  plexuses.     On  the 
other  hand,  as  the  fibres  are  preparing  to  enter  the  nervous  centres,  the 
membranous  tube  dilates  so  as  to  receive  a  nerve  vesicle,  Manner  of  re_ 
with  which  the  diaphanous  axis  cylinder  is  thus  brought  in  ceptionofvesi- 
contact.     Where  corpuscles  are  received  into  the  membran-  cles' 
ous  sheath,  it  is  not  always  certain  but  that  the  fibre  has  some  other 
termination  beyond.     Some  have  supposed  that  sensitive  fibres  differ 
from  the  motor  ones  in  the  circumstance  that  the  former  alone  are 
brought  in  connection  with  the  corpuscles,  but  this  is  very  unKkely. 

Second.  The  vesicular  nervous  substance  is  composed  of  nucleated 
cells  containing  a  granular  substance,  with  which  there  are  The  vesicular 
intermixed,  especially  near  the  nuclei,  pigment  granules.  P°rtion- 
These  granules,  however,  are  sometimes  absent,  as  in  the  vertebrata. 
The  nucleus  of  each  ganglionic  vesicle  often  presents  a  nucleolus ;  the 
diameter  of  the  vesicle  varies  from  -g-J^  to  1  2*5  Q  of  an  inch.  These  ves- 
icles are  found  in  the  nerve  centres,  their  coloring  material  communicat- 
ing to  those  parts  the  peculiar  tint  they  display.  In  shape  they  vary 
very  much,  some  being  spherical,  some  ovoid,  and  others  caudate,  ex- 
hibiting processes  which  are  filled  with  granules,  or  which,  becoming 
eventually  transparent,  communicate  with  similar  processes  from  other 
cells,  or  are  continuous  with  the  axis  cylinders  of  the  nerve-tubes.  Ac- 
cording to  Axmann,  the  axis  cylinder  is  a  continuation  of  the  nucleus 
of  the  cell.  The  ganglion  vesicles,  as  they  are  termed,  are  character- 
Fi  116  ized  by  containing  a  large  amount  of  phosphor- 

ized  oil,  and  it  is  probable  that  the  oxidation  of 
this  material  is  a  condition  of  their  functional  ac- 
tivity. 

Fig.  116,  ganglion  globules  (nerve-cells),  from 
the  Gasserian  ganglion  of  the  cat.  1.  Cell,  with 
short  pale  process,  showing  the  origin  of  a  fibre ; 
<z,  sheath  of  the  cell  and  nerve-tube,  containing  nu- 
clei ;  b,  cell  membrane  of  the  nerve-cell.  2.  Cell, 
with  the  origin  of  a  fibre  without  sheath ;  b,  cell 
membrane  of  the  nerve-cell.  3.  Nerve-cell,  de- 
prived, in  the  preparation  of  it,  of  its  membrane 
Nerve  W  magnified  awdi-  and  external  sheath.  (Kolliker.) 

Fig.  117,  p.  264,  bipolar  nerve-cell  of  the  pike, 

continued  at  each  end  into  nerve-tubes,     a,  sheath  of  the  nerve-cell ;  b, 
sheath  of  the  nerve ;  c,  medulla ;  d,  axis  cylinder  continuous  with  the 


264 


BIPOLAR   AND   MULTIPOLAR   NERVE-CELLS. 


contents  of  the  nerve-cell,  e,  which  have  shrunk  away 
from  the  sheath  after  action  by  arsenious  acid.  (Kol- 
liker.) 

Fig.  118,  caudate   nerve   vesicle  of  the  multiple 
kind:    a,  the    nucleated   vesicle;    b,  its    processes. 


Fig.  118. 


Bipolar  nerve-cell,  magni- 
fied 350  diameters. 


Fig.  119. 


Multipoint  nerve-cells,  magnified  200  diameters. 

These  probably  are  continuous  with  the  axis  cylin- 
ders of  the  nerves,  in  connection  with  the  vesicle. 
Fig.  119,  tubules  and  nerve-cells :  A,  from  sympa- 
thetic ganglion ;  *,  a  sepa- 
rate cell,  showing  its  pellu- 
cid nucleus  and  nucleolus : 
B,  from  the  gray  substance 
of  human  cerebellum:  <z,  b, 
plexus  of  primitive  fibres ; 
<?,  nucleated  globules ;  *, 
a  separate  cell  from  hu- 
man ganglion  of  Gasser. 
(Wagner.) 

Fig.  120,  tubules  and 
nerve-cells  of  human  brain :  A, 
nerve-cells  lying  in  the  midst 
of  varicose  nerve -tubes  and 
blood-vessels  in  the  substance 
of  the  optic  thalamus :  #,  glob- 
ule more  enlarged ;  £,  small  vas- 
cular trunk:  B,  B,  multipolar 
nerve-cells  from  the  dark  por- 
tion of  the  eras  cerebri.  (Pur- 
kinje.) 

Such  being  the  construction 
of  the  fibrous  and  vesicular  ma- 
terial, we  may  next  inquire  into 
their  functions. 


Nerve  cells  and  tubes,  magnified  353  diameters. 


B 


Human  nerve  tubules  and  cells. 


CENTRIPETAL  AND   CENTRIFUGAL  FIBRES.  265 

FUNCTIONS  OF  NERVE  FIBRES. 

That  the  function  of  nerve-tubes  is  to  conduct  impressions,  is  proved 
by  many  different  facts.  On  putting  a  ligature  round  a  nerve,  Functions  of 
or  cutting  it  across,  it  no  longer  transmits  the  usual  influ-  nerve  fibres- 
ences.  A  more  critical  examination  shows  that  impressions  made  on 
the  external  extremities  of  a  nerve  are  conveyed  by  it  to  the  centres, 
and  the  influences  originating  in  the  nervous  centres  are  conducted  along 
such  trunks  to  the  parts  to  which  they  are  distributed.  This  double 
duty  therefore  implies  that  there  are  two  classes  of  tubes,  the  centripetal 
and  centrifugal,  though  thus  far  no  structural  difference  between  them 
has  been  detected.  They  can  not  of  themselves  either  originate  impres- 
sions or  motions,  these  in  every  instance  arising  from  external  or  central 
agency.  The  centrifugal  fibres,  when  cut  across,  may  show  Centri  etal* 
no  effect  if  the  part  still  remaining  attached  to  the  nerve  cen-  and  centrifu- 
tre  is  irritated ;  but  if  the  other  part  connected  with  the  pe-  gal  fibres' 
riphery  be  pressed  upon  or  pinched,  muscular  contraction,  that  is,  mo- 
tion, results.  If  centripetal  fibres  be  examined  in  like  manner,  the  part 
connected  with  the  periphery  being  irritated,  no  result  arises ;  but  if 
the  part  connected  with  the  centre  be  irritated,  sensations,  general  or 
special,  as  the  case  may  be,  are  perceived.  These  several  effects  ensue 
when  the  motor  or  sensory  nerve  is  intact ;  for,  on  irritating  the  one  or 
the  other,  motion  or  sensation,  as  the  case  may  be,  is  produced.  If  the 
whole  trunk  of  a  centripetal  nerve  be  irritated,  the  mind  refers  the  sen- 
sation to  all  those  parts  to  which  the  branches  of  that  nerve  are  distrib- 
uted ;  if  a  part  only,  then  the  sensation  is  limited  to  those  portions  to 
which  the  fibrils  of  that  part  go ;  but,  besides  this,  the  mind  also  recog- 
nizes the  particular  spot  upon  the  trunk  to  which  the  irritation  has  been 
applied.  In  like  manner,  when  the  entire  trunk  of  a  centrifugal  nerve  is 
irritated,  all  the  muscles  which  it  supplies  contract ;  or,  if  only  a  part, 
then  those  muscles  which  are  supplied  from  that  part.  From  the  ana- 
tomical fact  that  a  nerve-tube  does  not  anastomose  with  its  neighbors, 
the  influences  which  it  conveys  are  transmitted  along  it  without  any  lat- 
eral diffusion,  and  every  fibre  discharges  one  duty,  and  one  Unity  of  func_ 
alone.  The  centripetral  can  never  assume  the  function  of  tion  in  the 
the  centrifugal ;  and  in  the  case  of  nerves  of  special  sense, 
there  is  the  same  restriction:  the  optic  nerve  can  not  transmit  the  im- 
pressions of  sounds,  nor  the  auditory  the  vibrations  of  light ;  the  nerves 
of  common  sensation  are  affected  neither  by  one  or  the  other,  but  they 
are  by  variations  of  temperature.  The  velocity  with  which  Rate  of  con_ 
these  influences  pass  along  nerve  fibres  is  indefinitely  less  ductitility  in 
than  that  with  which  electricity  moves  in  a  metal  conductor.  nerves- 
Thus  far,  however,  no  satisfactory  measure  of  it  has  been  obtained. 


266      ANALOGY  OF  NERVES  AND  ELECTRIC  CONDUCTORS. 

The  experiments  of  Helmlioltz  give,  for  the  rate  of  propagation,  from  83 
to  88  feet  per  second  in  the  frog,  and  in  man  200  feet,  the  velocity  ris- 
ing with  the  mean  animal  heat.  At  one  time  it  was  thought  that  there 
are  perceptible  differences  in  this  rate  in  the  same  nerve  of  different  indi- 
viduals, or  in  different  nerves  in  the  same  individual,  but  these  conclu- 
sions are  admitted  to  be  erroneous,  or  to  be  explained  upon  another  prin- 
ciple. It  can  not  be  denied  that  there  is  a  general  resemblance  between 
the  manner  in  which  a  nervous  fibril  transmits  its  influences  and  that  in 
which  a  conducting  medium  conveys  an  electric  current,  though  the  ve- 
Resembiance  locity  may  be  very  different.  There  is  a  resemblance  be- 
between  the  tween  the  arrangement  of  the  axis  cylinder  surrounded  by 
trical  conduct-"  ^s  white  substance  and  membranous  tube,  and  that  of  a  met- 
ors-  alline  wire  wrapped  round  with  silk,  or  other  non-conduct- 

ing material  in  many  electrical  arrangements.  An  electric  current  arti- 
ficially transmitted  along  a  nerve  trunk  will,  as  the  nature  of  that  trunk 
may  be,  give  rise  to  muscular  contraction,  or  produce  general  or  special 
sensations,  or  originate  reflex  action.  For  these  reasons,  it  has  long  been 
supposed,  by  many  physiologists,  that  the  influence  which  passes  along 
nervous  fibres  is  analogous  to  electricity,  if  it  be  not  identical  therewith ; 
but  all  attempts  to  prove  the  existence  of  an  electric  current,  either  in  the 
centripetal  or  centrifugal  fibres,  have  thus  far  been  abortive.  It  may, 
however,  be  remarked,  that  the  arguments  which  are  commonly  present- 
ed against  the  hypothesis  of  the  identity  of  the  nervous  agent  and  elec- 
tricity are  but  of  little  weight  when  critically  examined.  Thus  it  is  said 
that  an  electric  current,  passing  along  a  nerve  fibre,  spreads  laterally, 
whereas  the  nervous  agent  never  does ;  but  this  is  all  dependent  upon 
that  quality  formerly  known  among  electricians  as  intensity.  There  is 
no  reason  to  suppose  that  a  thermo-electric  current,  the  intensity  of  which 
is  very  low,  would  exhibit  such  a  lateral  propagation ;  whereas  a  voltaic 
current,  whose  intensity  is  high,  does  it  without  difficulty.  Moreover, 
though  it  has  been  stated  that  the  electric  conductibility  of  a  nervous 
trunk  is  indefinitely  worse  than  that  of  a  metal,  even  lower  than  that  of 
a  bundle  of  muscular  fibre,  it  should  be  remembered  in  these  discussions 
that  the  conducting  power  is  in  the  axis  cylinder,  and  no  attempt  has 
ever  yet  been  made  by  any  experimenter  to  isolate  that  structure  and  sub- 
mit it  to  proper  examination.  It  is  just  the  same  as  though  we  should 
take  a  bundle  of  copper  wires,  each  one  of  which  is  separated  from  its 
neighbors  by  a  layer  of  non-conducting  fat ;  that  we  should  cut  out  a  sec- 
tion of  such  a  construction  with  a  pair  of  scissors,  and  then  attempt  to 
determine  its  conductibility.  That,  under  any  circumstances,  would  be 
low  enough ;  and  the  chances  are  that  the  non-conducting  material  would 
be  smeared  over  the  ends  in  the  act  of  making  the  section,  and  the  speci- 
men refuse  to  conduct  at  all.  In  a  similar  manner,  we  may  dispose  of 


OF  NERVE-CELLS. 


267 


all  those  experiments  which  have  been  brought  to  prove  the  dissimilari- 
ty of  electricity  and  the  nervous  agent,  by  intervening  a  piece  of  metal 
between  a  section  of  a  nervous  trunk,  it  having  been  found  that  under 
such  circumstances  the  nervous  influence  does  not  pass. 

The  physical  condition  upon  which  the  activity  of  the  nervous  mech- 
anism depends  is  the  supply  of  arterial  blood ;  for,  although  Nervous  activ 
the  nerve  fibres  never  receive  or  are  penetrated  by  blood  cap-  ity  depends  on 
illaries-,  these  latter  run  in  company  with  them  in  the  nerv-  artenal  b 
ous  fasciculi.  It  would  appear,  however,  that  the  supply  of  arterial  blood 
is  of  far  less  moment  in  the  function  of  the  nerve  fibres  than  it  is  in  that 
of  the  nerve  centres.  This  is  shown  by  the  limited  supply  given  to  the 
former,  and  the  abundant  one  to  the  latter ;  by  the  comparative  effect  of 
a  stoppage  of  the  blood  circulation,  in  which  case  the  action  of  the  nerve 
centres  is  instantly  arrested,  whereas  that  of  the  fibres  may  continue  for 
a  long  time.  On  the  whole,  there  are  strong  reasons  for  believing  that 
the  conductibility  of  the  nerve  fibres  is  as  purely  physical  as  is  that  of  a 
metal  wire,  and  that  the  supply  of  blood  that  they  receive  is  only  for  the 
purpose  of  maintaining  their  construction  in  a  perfect  state. 

We  have  stated  that  there  are  nerves  the  functions  of  which  are  essen- 
tially different,  such  as  the  centripetal  .or  sensory,  and  the  identification 
centrifugal  or  motor.      The  identification   of  the  class  to  of  the  class  of 
which  a  nerve  under  examination  belongs,  may  sometimes 
be  made  by  examining  its  manner  of  distribution,  or  its  ganglionic  con- 
nection ;  sometimes  by  experiment,  by  making  a  section  and  irritating 
the  cut  extremities.     In  these  cases,  however,  caution  has  to  be  exer- 
cised in  coming  to  a  conclusion. 

FUNCTIONS  OF  NERVE-CELLS. 

.The  neTvous  fibres  having  for  their  duty  the  conduction  of  external 
impressions  and  the  transmission  of  nervous  influences,  the  Function  of 

Fig.  121.  nerve-cells  or  nerve  vesicles- 

^ '  '     vesicles   are   for   the    re- 

ception of  those  impres- 
0    sions  and  the  origination 
of  those  influences.     The 
nerve  centres  or  ganglia 
are  made  up  of  vesicles, 
granules,  and  nerve-tubes 
ft  conjointly. 

Fig.  121,  dorsal  gan- 
glion of  the  sympathetic 
nerve  of  a  mouse.  $,  b, 

Dorsal  ganglion  of  mouse.  COl'ds    of   Connection    With 


268  VESICLES   ARE   MAGAZINES   OF   FORCE. 

adjacent  ganglia ;  <?,  c,  ct  <?,  branches  to  the  viscera  and  spinal  nerves  ;  d, 
nerve-cells ;  e,  nerve-tubes  traversing  the  ganglion.  (Valentin.) 

For  the  explanation  of  the  function  of  the  nerve  centres,  it  is  essential- 
Function  of  ly  necessary  that  we  should  have  clear  views  of  the  function 
Sedanatom-  ofthe  nerv<3  vesicles.  It  has  appeared  to  me  that  their  duty 
icaiiy.  is  manifested  by  their  anatomical  relations.  The  influence, 

whatever  it  may  be,  which  passes  along  a  nervous  cord,  is  completely 
isolated  therein,  and  never  leaves  the  fibril  in  which  it  is  passing  from 
its  origin  to  its  termination.  It  is  isolated  by  the  white  substance  of 
They  permit  Schwann.  But  it  is  very  plain,  as  a  thousand  phenomena 
esca^ 'intcT *°  °^  ^ie  nervous  system  prove,  that  there  are  places  of  escape 
new  channels,  for  this  influence,  although  it  may  be  confined  in  the  nerve- 
tube,  and  these  places  can  be  no  other  than  the  vesicles.  Their  caudate 
aspect,  or  multipolar  form,  as  it  is  often  termed,  will  bear  no  other  inter- 
pretation. The  disturbing  influence,  coming  along  the  axis  cylinder  of  a 
nerve-tube,  finds  itself  delivered  into  the  granular  material  in  the  interior 
of  a  vesicle,  a  material  physically  continuous,  in  the  opinion  of  many 
physiologists,  with  the  structure  of  the  axis  cylinder.  Through  this 
granular  material  the  influence  is  transmitted,  and  if  the  vesicle  should 
have  on  its  distant  contour  two  or  more  nerve-tubes  connected  with  it, 
it  would  seem  to  be  the  necessary  result  of  such  a  state  of  things  that 
the  influence  will  pass  down  all  those  channels.  For  these  reasons  I  re- 
gard the  nerve  vesicles  as  being  constructions  for  the  purpose  of  'opening 
out  the  closed  nerve  tubules,  and  permitting  them  to  deliver  their  energy 
into  new  tracts. 

But  more  than  this.  Whatever  may  be  the  manner  in  which  the 
Diffusion  of  in-  nervous  influence  is  propagated,  or  conducted  from  point 
granular  mate!  *°  Pom*  °^  tne  granular  material  within  the  vesicle,  there 
rial.  must  be  now,  since  there  is  no  structure  to  prevent  it,  a  lat-* 

eral  spreading  of  effect.  It  is  not  to  be  supposed  that  the  passage  is 
made  in  a  direct  line,  from  the  terminus  of  the  centripetal  to  the  origin 
ofthe  centrifugal  fibre,  across  these  caudate  vesicles,  and  restricted  there- 
to. There  is  no  isolator  to  confine  it  in  any  such  track,  and  it  seems  to 
follow  of  necessity  that  the  whole  contents  of  the  vesicle  must  be  affect- 
Vesicles  retain  ed,  and  this  irrespective  of  its  magnitude.  Such  a  condition 
a™drarTma'«-a-  °^  tnmgs  introduces  the  suspicion  of  a  second  great  duty 
zines  of  force,  which  the  vesicles  may  discharge  in  retaining  within  them- 
selves, at  all  events  for  a  short  period,  the  influences  that  have  thus  es- 
caped laterally,  and  thus  they  become  temporary  magazines  of  power. 
Unipolar,  bi-  And  perhaps  this  may  be  the  true  interpretation  ofthe  action 
polar,  muitipo-  of  unipolar  and  bipolar  vesicles;  the  unipolar  being  a  capsule 
for  the  collection  and  conservation  of  the  entire  delivered  in- 
fluence, the  bipolar  to  admit  of  the  passage  onward  of  a  large  portion  of 


RETENTION   AND   INTEEFEEENCE    OF   IMPEESSIONS.  2G9 

the  force,  but  by  lateral  diffusion  to  preserve  or  delay  a  part,  and  the 
multipolar  at  once  permitting  of  conservation  and  of  a  discharge  into, 
perhaps,  a  multitude  of  new  channels. 

Upon  the  same  principle  that  multicaudate  vesicles  permit  of  the  es- 
cape of  nervous  influence  from  the  single  channel  in  which  it  interference  of 
has  been  coming  into  many  new  ways,  so  likewise  they  impressions, 
must  be  the  seats  of  the  interference  of  influences  delivered  into  them 
from  many  centripetal  fibres  at  the  same  time.  Thus  we  may  imagine 
a  tricaudate  vesicle  into  the  granular  material  of  which  an  influence  is 
delivered  simultaneously  by  two  centripetal  fibrils,  and  these,  reacting  on 
one  another  in  the  interior  of  the  vesicle,  give  rise  to  a  resultant  which 
may  differ  from  them  both,  and  this  is  passed  on  through  the  third,  the 
centrifugal  fibril. 

Regarded  in  this  way,  the  function  of  a  nerve  vesicle  may  therefore  be 
stated  to  be,  1st.  To  permit  the  escape  of  an  entering  influence  out  of  the 
solitary  channel  in  which  it  has  been  isolated  into  any  number  of  diverg- 
ing tracts ;  2d.  -To  combine  influences  which  are  entering  it  from  various 
directions  into  a  common  or  new  result ;  3d.  By  permitting  of  lateral  dif- 
fusion to  take  off  and  keep  in  store  for  a  certain  duration  a  part  of  the 
passing  influence. 

Our  attention  can  not  fail  to  be  arrested  by  this  last  effect ;  for  if  there 
be  a  property  which  is  characteristic  of  the  nervous  mechan-  ^ 

.  n,  .  Retention  of 

ism  in  its  utmost  degree  ot  development,  it  is  this  of  retain-  the  vestiges  of 
ing  the  relics  or  traces  of  impressions  which  have  formerly  imPressions- 
been  made  upon  it.  As  it  goes  on  increasing  in  perplexity  as  we  rise 
through  the  animal  series,  the  provision  for  the  retention  of  such  impres- 
sions becomes  more  and  more  strikingly  marked.  Ganglionic  masses, 
which,  from  their  position  and  structure,  are  marked  out  for  this  duty, 
appear  in  that  ascending  scale  in  increasing  magnitude.  To  these  we 
may  aptly  apply  the  designation  of  registering  ganglia,  since  Registering 
they  truly  store  up  the  traces  of  ancient  impressions  and  keep  ganglia. 
them  in  reserve.  These  ganglia  must,  moreover,  be  the  scenes  of  the  in- 
teraction and  interference  of  the  impressions  they  thus  contain. 

The  registering  ganglia  thus  introduce  the  element  of  time  into  the  ac- 
tion of  the  nervous  mechanism.  The  impression  which  T 

<•"*"»  i  -i    -i   •  •         •      i        Introduction 

without  them  would  have  forthwith  ended  in  action  is  de-  of  the  element 
layed  for  a  season,  nay,  perhaps  even  as  long,  though  it  may  °  me< 
be  in  a  declining  way,  as  the  structure  itself  endures ;  and  with  the  in- 
troduction of  this  condition  of  duration  come  all  those  important  effects 
which  ensue  from  the  various  action  of  many  received  impressions,  old 
and  new,  upon  one  another. 

This  internal  origination  of  new  results  through  the  interaction  of  im- 
pressions retained  in  the  registering  ganglia  is  too  important  a  phenom- 


270  VARIABLE   EFFECTS   FROM   INVARIABLE    CAUSES. 

enon  to  "be  passed  lightly  by,  more  especially  when  we  consider  the  sur- 
prising results  to  which  it  eventually  leads  in  the  higher  forms  of  life.  I 
Illustration  of  sna^  therefore,  without  any  apology,  digress  briefly  for  the 
the  production  sake  of  illustrating  my  meaning,  by  showing  how,  even  in 
suits^yinvari-  the  material  world,  from  conditions  which  are  as  fixed  as  fate, 
able  causes.  through  interaction  of  consequences  variable  results  arise. 

The  laws  of  nature,  being  founded  on  pure  reason,  are  absolutely  un- 
changeable. Of  the  things  which  are  presented  to  our  contemplation, 
they  alone  are  invariable.  Material  substances  of  every  kind  wear  by 
time,  and  exhibit  incessant  alterations,  and  this  the  same  whether  they 
are  of  a  terrestrial  or  a  celestial  kind.  There  are  tides,  eclipses,  seasons, 
births,  deaths.  Throughout  the  universe  there  is  no  monument  that  re- 
tains its  primordial  condition;  for  all  material  aggregations  are  only 
forms,  and  every  form,  in  the  process  of  time,  must  perish.  There  are 
changes  of  the  surface  of  the  earth,  changes  in  its  position  as  to  the  sun, 
changes  in  the  places  of  systems  of  worlds  as  to  one  another.  Every 
thing  is  at  every  moment  in  motion ;  but  in  the  midst  of  all,  every  law 
of  nature,  as,  for  example,  the  law  of  gravitation,  endures  without  varia- 
tion for  an  instant,  and  is  never  for  an  instant  suspended. 

This  invariability  of  natural  laws  from  age  to  age,  even  under  circum- 
stances in  which  we  might  suspect  a  change,  is  illustrated  by  the  parallel 
which  may  be  traced  between  the  development  of  the  most  recent  em- 
bryos, as  of  man,  and  those  of  the  ancient  geological  times,  or  between 
human  development  and  that  of  the  whole  animal  series.  In  all  these 
cases  such  a  phenomenon  is  never  witnessed  as  that  of  a  part  springing 
from  nothing :  it  conies  out  of  something  existing  before,  and  exists  as  a 
consequence  of  some  preceding  act.  The  order  in  which  part  arises  from 
part  is  the  same  now  as  it  has  been  in  all  times — the  same  in  organ- 
isms which  are  most  distinct  from  each  other  in  structure  or  position  in 
the  natural  scale ;  and  thus  we  see  that  development  is  not  only  the  con- 
sequence of  law,  but  of  law  which  is  unchangeable  and  universal  in  its 
application. 

As  with  these  phenomena  of  development  and  all  natural  facts,  so  with 
the  operations  of  the  mind.  There  is  no  such  thing  as  a  spontaneous  or 
self-originating  thought.  Every  intellectual  act  is  the  consequence  of 
some  preceding  act.  It  conies  into  existence  in  virtue  of  something  that 
has  gone  before.  Two  minds  constituted  precisely  alike,  and  placed 
under  the  influence  of  precisely  the  same  external  physical  circumstances, 
must  give  birth  to  precisely  the  same  thought.  Such  is  plainly  the 
consequence  of  that  invariability  and  universality  of  the  laws  of  nature 
on  which  I  have  been  insisting,  which  is  illustrated  by  the  fact  we  so  often 
witness  in  our  daily  affairs,  and  strikingly  in  the  case  of  philosophical 
discoveries,  the  same  idea  occurring  to  many  persons  at  the  same  time. 


REGISTERING   GANGLION.  271 

It  is  this  sameness  of  action  to  which  we  allude  in  that  popular  expres- 
sion, common  sense— a  term  full  of  meaning.  In  the  origination  of  a 
thought  there  are  two  distinct  conditions  involved — the  state  of  the  mind 
as  dependent  on  antecedent  impressions,  and  the  existing  physical  cir- 
cumstances. The  brain  is  the  instrument  on  which  external  circum- 
stances play ;  but  in  the  same  manner  that  the  course  of  time  presents 
us  with  natural  vicissitudes,  such  as  night  and  day,  the  seasons,  the  tides, 
spring  and  neap,  with  their  ebb  and  flow,  variations  of  events  may  ensue, 
notwithstanding  the  fate-like  aspect  of  the  acting  law,  and  this  through 
the  interaction  of  consequences.  So  the  earth  revolves  round  the  sun 
as  a  consequence  of  gravity,  and  for  the  same  reason  does  the  moon  re- 
volve round  the  earth ;  for  the  same  cause  do  the  tides  flow  and  ebb  in 
the  sea ;  yet  there  will  be  spring  tides  when  the  sun  and  moon  draw  in 
one  direction,  and  neap  tides  when  they  draw  in  opposite  ways.  Out  of 
the  invariable  the  variable  may  therefore  arise. 

To  return  from  this  digression  to  the  phenomena  displayed  by  regis- 
tering ganglia,  in  continuation  of  the  views  offered,  I  may  pre-  Illustration  of 
sent  as  an  example  the  manner  in  which  I  should  be  disposed  ^8y™jj  in 
to  regard  in  this  respect  the  entire  nervous  system  of  the  ar-  sects. 
ticulata.  Constructed  as  these  animals  are  upon  an  axis,  the  nerves 
which  are  given  off  from  the  ganglia  upon  that  axis  right  and  left,  a  pair 
for  each  segment,  are  primarily  purely  automatic,  and  act  therefore  pri- 
marily in  a  purely  reflex  way ;  an  impression  made  on  the  peripheral  ex- 
tremity of  one  of  their  centripetal  fibres  is  conducted  to  the  ganglion, 
passes  through  it,  escapes  along  the  centrifugal  fibre,  and  a  motion  oc- 
curs. But  the  whole  influence  is  not  thus  promptly  disposed  of.  A  part 
of  it  is  conducted  by  commissural  strands  to  the  cephalic  ganglia,  and 
there  held  in  reserve.  And  the  same  thing  holds  good  for  ev-  Function  of 
ery  one  of  the  ganglia  of  the  ventral  cord,  so  that  for  them  all  the  cephalic 
the  cephalic  become  a  point  of  common  convergence,  or,  in  my  gang  ia' 
view,  the  common  register  for  them  all.  Here,  at  this  focal  point,  are 
stored  up  the  relics  of  whatever  impressions  have  been  made  upon  the 
common  peripheral  nerves,  and  here  are  received  those  which  are  brought 
from  the  structures  of  special  sense — the  visual,  the  auditory,  the  olfac- 
tory, if  any.  There  does  not,  then,  appear  any  great  difficulty  in  ex- 
plaining the  well-marked  deviations  from  automatism  which  these  ani- 
mals may  present. 

The  action  of  every  ganglionic  mechanism  depends  upon  the  existence 
of  certain  physical  conditions,  among  which,  as  being  of  par-  Nerve  centres 

-,        -, .  ^        T ,    .      ,  i        -J         can  not  act  ex- 

amount  importance,  one  may  be  discerned.     It  is  the  due  cept  by  oxj(ia. 
supply  of  arterialized  blood.     If  this  be  stopped  but  for  a  tion- 
moment,  the  nerve  mechanism  loses  its  power,  or  if  diminished,  the  dis- 
play of  its  characteristic  phenomena  correspondingly  declines.     If,  on 


272  WASTE   AND   REPAIR   OF   NERVOUS   MATTER. 

the  contrary,  the  supply  be  unduly  great,  or  its  oxidizing  power  artificial- 
ly increased,  there  is  a  more  energetic  action.  This  latter  condition  of 
things  is  presented  in  the  earlier  stages  of  the  respiration  of  protoxide  of 
nitrogen,  an  increased  muscular  power,  and  an  exaggeration  of  the  pro- 
cesses of  intellection.  The  opposite  state  is  witnessed  when  carbonic 
acid,  more  or  less  dilute,  is  breathed,  from  that  blunting  of  the  intellectual 
faculties  and  indisposition  for  muscular  exertion  which  is  felt  in  ill-ven- 
tilated apartments  where  carbonic  acid  is  permitted  to  accumulate,  to  the 
profound  torpor  and  insensibility  experienced  when  it  is  in  a  more  con- 
centrated state.  These  exaltations  and  depressions  of  the  capabilities  of 
the  nervous  instrument  are,  therefore,  clearly  of  a  chemical  kind,  and  may 
be  produced  artificially  and  at  pleasure  by  the  respiration  of  appropriate 
gases  or  the  administration  of  certain  drugs.  Nay,  even  the  accumula- 
tions of  the  effete  products  of  the  economy  are  sufficient  to  give  rise  to 
such  diminutions  of  power,  as  we  see  when  bile  or  urea  is  permitted  to 
accumulate  in  the  blood.  The  therapeutical  and  toxicological  influences 
of  certain  medicaments  are  illustrations  of  these  principles.  Of  such 
substances,  some  act  on  the  sensorial  and  some  on  the  motor  powers, 

The  copious  distribution  of  arterial  blood  to  the  nervous  centres  indi- 
Necessityofre-  cates  that  they  undergo  a  rapid  waste.  That  supply  can 
pair  and  rest.  no^  -j^  for  ^he  mere  purposes  of  growth  alone,  since,  when 
once  maturity  is  reached,  the  nervous  mechanism  presents  but  little  ex- 
pansion. The  provision  for  nutrition  assures  us  that  that  action  must 
be  rapidly  going  on ;  but  the  equilibrium  of  the  system  betrays  that  such 
nutrition  is  not  for  development,  but  for  the  repair  of  waste ;  and,  in- 
deed, this  waste  proceeds  at  such  a  rate  that  there  arises  in  some  portions 
of  this  system  a  necessity  for  periodic  repose,  a  time  for  the  restoration 
of  the  parts.  If  any  arguments  were  required  to  establish  beyond  dis- 
pute that  such  a  disintegration  of  the  material  of  the  nerve  centres  does 
occur,  it  would  be  furnished  by  an  examination  of  the  urine ;  for,  in  nerv- 
ous substance,  phosphorus  occurring  as  a  characteristic  ingredient,  it 
must  give  rise  to  the  production  of  phosphoric  acid,  or  salts  thereof,  in 
Destruction  of  the  supposed  periods  of  activity.  Moreover,  in  this  meta- 
nervous  mate-  morphosis  of  the  vesicular  structure  ammonia  must  eventu- 
portiontonerv-  ally  arise,  from  the  cell  walls  if  from  no  other  source,  and 
ous  activity,  accordingly  we  find  in  the  urine  that  characteristic  double 
salt,  the  phosphate  of  soda  and  ammonia.  The  amount  of  these  alkaline 
phosphates  has  long  been  known  to  be  in  proportion  to  the  activity  of 
the  nervous  system,  particularly  in  the  case  of  individuals,  such  as  cler- 
gymen, whose  mental  powers  are  taxed  unduly  at  stated  intervals.  The 
general  fact  that  the  degree  of  energy  which  this  system  exhibits  is  de- 
pendent on  the  activity  of  respiration  in  different  tribes  of  life  might  be 
established  from  many  familiar  instances. 


COMPOSITION   OF   NERVOUS   MATTER. 


273 


More  precise  ideas  would  be  arrived  at  regarding  the  waste  of  the  nerv- 
ous mechanism  if  we  possessed  a  more  accurate  knowledge  of  its  chem- 
ical constitution.  The  examinations  hitherto  made  are  far  ~ 

Composition  of 

from  agreeing  with  one  another,  and  this,  to  a  certain  extent,  nervous  mate- 
is  due  to  the  difficulty  of  obtaining  the  true  nervous  tissue  in  nal' 
an  isolated  state,  or  unmingled  with  other  intervening  structures.  *  The 
following  tables  will  give,  however,  a  general  idea  of  its  composition  at 
different  periods  or  in  different  conditions. 

Analysis  of  Brain  of  different  Conditions  of  Life.     (From  L'Heritier.) 


Infants. 

Youths. 

Adults. 

Aged. 

Idiots. 

Water 

827  90 

742.60 

725.10 

738  50 

709  30 

Albumen  

70.00 

102.00 

94.00 

86.50 

84  00 

Fat 

34  50 

53.00 

61.00" 

43.20 

50  00 

Osmazome  and  salts 
Phosphorus  

59.60 
8.00 

85.90 
16.50 

101.90 
18.00 

121.80 
10.00 

148.20 
8.50 

1000.00 

1000.00 

1000.00 

1000.00 

1000.00 

Composition  of  Spinal  Cord  of  Adult.     (From  L'Seritier.") 

Water 710.50 

Albumen 73.00 

Fat 82.50 

Osmazome  115.00 

Phosphorus  19.00 

1000.00 

Analysis  of  Medullary  and  Cortical  Substance  of  Brain  of  Idiot.     (From  Lassaigne.) 


Cortical  and  Med- 
ullary together. 

Cortical. 

Medullary. 

Water  

770.00 

850.00 

730.00 

96.00 

75.00 

99.00 

Colorless  fat  

72.00 

10.00 

139.00 

Red  fat     

31.00 

37.00 

9.00 

Extractive,  lactic  acid,  and  salts... 
Phosphates  of  lime,  magnesia,  and 
peroxide  of  iron  

20.00 
11.00 

14.00 
12.00 

10.00 
13.00 

1000.00 

998.00 

1000.00 

From  which  it  would  appear  that  the  percentage  of  water  is  greatest  in 
the  early  periods  of  life,  and  that  of  phosphorus  in  the  adult.  Attention 
may  also  be  drawn  to  the  fact  that  the  percentage  of  phosphorus  in  the 
brain  of  idiots  is  very  low.  It  also  appears  that  the  constitution  of  the 
white  and  gray  portions  of  the  brain  is  different,  as  might  have  been  an- 
ticipated from  tlieir  appearance,  the  color  of  the  latter  being  due  to  a 
brown  fat.  By  some  it  is  supposed  that  the  non-saponifiable  fat  cho- 
lesterine  arises  as  a  product  of  waste,  and  that  the  phosphorized  oils,  as 
they  are  termed,  constitute  the  white  enveloping  cylinder  known  as  the 
white  substance  of  Schwann,  and  that  the  interior  cylinder  is  a  nitrogen- 
ized  but  non-phosphorized  body ;  but  there  are  reasons  for  suspecting 
that  the  white  substance  of  Schwann  is  a  non-phosphorized  fat,  and  that 
.the  axis  cylinder  contains  the  phosphorus  in  an  unoxidized  state,  prob- 
ably as  a  highly  phosphorized  protein  body.  Every  thing  seems  to  in- 

S 


274  VESICULAR   MATTER. 

dicate  that  Schwann's  substance  only  discharges  the  physical  duty  of 
an  isolator.  The  coincidence  between  the  varying  activity  of  the  nerv- 
ous mechanism  and  the  varying  quantity  of  oxidized  compounds  of  phos- 
phorus in  the  urine  indicates  in  a  significant  manner  that  this  chemical 
element  bears  something  more  than  a  passive  relation  to  the  processes 
going*  forward ;  and  its  known  occurrence  in  the  vesicular  structures,  to- 
gether with  its  extraordinary  chemical  relations,  would  prepare  us  to  ex- 
pect that  it  is,  in  reality,  intimately  concerned  in  all  these  phenomena. 
Vesicular  nervous  material  contains  much  less  fatty  matter  than  the 
.  tubular,  but  much  more  water.  Thus  HaufF  and  Walther 

Composition  of 

vesicular  mat-  found  in  the  gray  substance  of  the  brain  from  85  to  86  per 
ter'  cent,  of  water,  and  only  from  4.8  to  4.9  of  fat;  but  in  the 

corpus  callosum  they  found  70.2  per  cent,  of  water,  and  from  14.5  to 
15.5  of  fat.  From  such  facts  it  would  appear  that  the  presence  of  fat  in 
nervous  material  is  functionally  connected  with  its  property  of  conduc- 
tion or  transmission  of  nervous  influence.  In  the  brain  of  a  child  which 
died  at  birth,  Schlossberger  found  that  the  corpus  callosum  contained  as 
much  water  as  the  gray  matter,  and  that,  compared  with  the  brain  of 
adults,  that  of  new-born  infants  is  richer  in  water  and  poorer  in  fat.  Von 
Bibra  ascertained  that,  within  certain  limits,  the  quantity  of  fat  is  con- 
stant in  the  brain ;  that  a  diminution  or  increase  of  fat  in  other  parts  of 
the  system  is  not  accompanied  by  any  change  in  the  quantity  of  brain- 
fat  ;  that  the  proportion  of  fat  in  the  brain  of  man,  other  mammals,  birds, 
amphibia,  and  fishes,  diminishes  in  the  order  in  which  their  names  are 
here  mentioned ;  that  the  medulla  oblongata  contains  the  largest  per- 
centage of  fat ;  that  the  quantity  of  brain-fat  in  old  men  is  a  little  less 
than  that  of  adults  in  the  prime  of  life.  He  also  concludes  that  the 
amount  of  phosphorus  in  brain-fat  is  nearly  the  same  in  man,  other  mam- 
•  mals,  and  birds ;  that  its  percentage  in  the  brain  of  the  insane  does  not 
exceed  thef  mean  amount ;  that  the  vesicular  matter  contains  more  phos- 
phorus than  the  white;  and  that  there  is  no  special  connection  .between 
the  intelligence  and  the  amount  of  phosphorus  ;  that  the  amount  of  fat  in 
the  brain  of  the  foetus  is  much  less  than  that  of  the  adult,  the  difference 
being  made  up  by  an  excess  of  water,  but  that  a  great  and  sudden  aug- 
mentation of  fat  occurs  toward  the  end  of  foetal  existence. 

Our  attention  may  next  be  directed  to  the  methods  of  repair  of  the 
Mode  of  re  air  ves^cu^ar  structures.  Their  waste,  as  just  established,  im- 
of  nervous  plies  their  repair.  Here,  as  in  the  muscular  tissues,  the 
blood-vessels  conduct  both  operations,  and  the  mode  of  dis- 
tribution of  the  capillaries  is  such  as  to  bring  the  circulating  current  into 
the  most  favorable  position  for  discharging  this  duty.  The  vesicles  are 
included  in  the  midst  of  a  network  of  capillaries,  and  it  is  believed  that 
there,  is  a  resemblance  between  their  mode  of  growth  and  that  of  the  cells 


CHOLESTERINE   AND   PHOSPHORUS.  275 

of  the  epidermis ;  that  is  to  say,  they  arise  from  nuclei  on  the  spaces 
which  are  nearest  to  the  supply  of  "blood,  and  gradually  undergo  devel- 
opment as  they  prepare  for  connection  with  the  tubular  tissue,  assuming 
the  place  of  cells  that  have  discharged  their  function  and  are  undergoing 
disintegration.  This  gradual  passing  onward  and  wearing  away  recalls 
the  changes  in  the  structure  of  the  cuticle. 

To  two  of  the  substances  thus  met  with  in  these  examinations  of  the 
nervous  system  our  attention  may  be  profitably  directed.  Chole  rin 
These  are  cholesterine  and  phosphorus.  Of  the  former  we  and  phospho- 
can  not  have  failed  to  remark  that  it  is  a  constant  ingredient  rus* 
in  the  product  of  the  action  of  the  liver.  It  is  a  lipoid,  and  is  found  in 
biliary  calculi ;  and  though  it  may  be  regarded  in  one  sense  as  an  excre- 
mentitious  body,  since  it  occurs  in  faecal  matter,  yet  it  also  appears  as 
a  normal  constituent  of  the  blood.  It  may  therefore  be  inferred,  if  the 
opinion  of  its  existence  in  the  white  substance  of  Schwann  be  correct, 
that  it  is  one  among  the  various  functions  of  the  liver  to  prepare  this 
body.  Of  phosphorus  it  might  be  said,  that  it,  among  the  chemical 
elements,  is  most  strikingly  characterized  in  its  active  state  by  the  in- 
tensity of  its  affinity  for  oxygen.  On  this  depends  its  quality  of  shining 
in  the  dark,  a  quality  which  has  given  it  a  name ;  but  by  many  agents, 
such,  for  example,  as  exposure  to  a  particular  temperature,  and  especially 
to  the  light  of  the  sun,  it  may  be  thrown  into  a  condition  so  completely 
passive  that  its  chemical  energies  disappear.  The  doctrine  that  was  pre- 
sented in  explanation  of  the  destruction  of  one  part  of  the  system  by  the 
air  introduced  by  respiration  while  another  is  protected  therefrom,  as  de- 
pendent on  the  allotropic  condition  of  those  parts,  is  presented  here  again 
in  discussing  the  destruction  and  repair  of  the  nervous  tissue ;  for  it  is 
only  when  it  is  ready  to  be  removed  that  the  phosphorized  constituent 
assumes  the  active  state,  and  in  so  doing  gives  rise  to  the  development 
of  force.  On  this  view,  it  would  appear  that  such  phosphorized  com- 
pounds are  obtained  from  the  vegetable  kingdom  in  the  food  in  a  passive 
state,  the  tissues  of  plants  having  deoxidized  them  under  the  influence 
of  the  sunlight,  which  simultaneously  has  thrown  them  into  the  condi- 
tion of  inactivity,  and  perhaps  it  is  the  assumption  of  that  very  condition 
that  is  the  fundamental  cause  of  their  deoxidation. 

By  the  aid  of  the  conclusions  to  which  we  have  come  respecting  the 
function  of  nerve-tubes  and  vesicles,  as  betrayed  by  their  an-  Functions  of 
atomical  structure,  we  shall  not  have  much  difficulty  in  ex-  n^e1^e"osnand 
plaining  the  offices  of  nervous  arcs  presently  to  be  described,  sidered  eiec- 
The  results  at  which  we  thus  arrive,  from  a  consideration  of  trically- 
those  cells,  are  singularly  fortified  by  the  electrical  experiments  of  Gal- 
vani,  Volta,  Nobili,  and  especially  those  of  Volkmann.     Among  these, 
the  three  following  are  of  primary  importance : 


276  VOLKMANN'S  ELECTEICAL  EXPERIMENTS. 

1st.  When  a  continuous  electrical  current  is  passed  along  a  centrifu- 
Voikmann's  ga^  nerve,  contraction  of  the  muscles  which  that  nerve  supplies 
results.  takes  place,  and  continues  as  long  as  the  electric  current  pass- 
es, without  relaxation,  but  ceases  the  moment  the  current  is  stopped. 

2d.  When  a  continuous  electric  current  is  passed  through  a  ganglion, 
contraction  of  the  muscles  supplied  by  the  centrifugal  nerves  of  that  gan- 
glion ensues.  These  contractions  do  not  .alternate  with  relaxation,  and 
on  stopping  the  current  the  contraction  does  not  cease  as  in  the  preced- 
ing case,  but  is  continued  for  a  period  of  time. 

3d.  When  a  continuous  electric  current  is  passed  down  a  centripetal 
nerve,  muscular  contraction  of  the  parts  supplied  by  the  corresponding 
centrifugal  nerves  occurs,  and  these  contractions  alternate  with  relax- 
ations. 

In  view  of  these  facts,  we  are  brought  to  two  conclusions :  First,  that 
there  is  a  property  in  the  ganglion  which  enables  it  to  hold  in  reserve  a 
portion  of  the  influence  brought  into  it,  so  as  to  keep  up  the  action  for  a 
period  of  time  after  the  original  disturbing  causes  have  ceased.  Second, 
that  the  structure  of  the  ganglion  is  such  as  to  permit  the  escape  of  the 
coming  influence  by  lateral  ways,  either  periodically  or  otherwise,  and  so 
to  produce  from  a  continuous  influence  an  intermitting  effect. 

Kecalling  the  fact  that  a  ganglion  is  made  up  of  nerve-tubes  and  vesi- 
cles conjointly,  these  electrical  results  must  find  their  solution  in  the  el- 
ementary structure  of  the  ganglion,  that  is  to  say,  in  its  vesicular  por- 
tion ;  for  it  is  not  to  be  supposed  that  a  current  of  electricity,  such  as  we 
are  here  considering,  would  ever  have  an  opportunity  of  escaping  from 
the  axis  cylinder  along  which  it  passes.  The  isolating  quality  of  the 
white  cylinder  of  Schwann  would  prevent  any  such  effect.  It  is  not  nec- 
essary that  we  should  embarrass  ourselves  here  with  the  fact  that  elec- 
tric currents  of  sufficient  intensity  could  make  their  way  out  from  the  in- 
terior channel  in  spite  of  its  insulating  investiture,  since  it  is  only  with 
those  of  a  far  less  power  that  we  have  to  deal.  Arrived  in  the  vesicle, 
the  current  at  once  diffuses  itself  throughout  the  granular  material,  just 
in  the  same  manner  that  it  would  diffuse  throughout  a  spherical  conduct- 
ing mass  if  brought  to  it  by  a  wire,  and  escape  therefrom  through  any 
number  of  similar  wires  that  might  chance  to  be  in  contact  with  the  con- 
ducting mass  beyond ;  and  though  the  main  body  of  the  current  would, 
as  may  be  readily  proved,  under  these  circumstances  move  in  a  direct 
line  from  the  point  of  entry  to  the  point  of  exit,  there  would  be  neverthe- 
less a  diffusion  of  part  of  it  through  the  conducting  mass,  no  portion 
thereof  remaining  unaffected.  In  a  good  conductor,  such  as  a  metal,  this 
laterally  diverging  current  would  instantly  escape,  but  the  case  becomes 
very  different  in  the  less  perfectly  conducting  material,  the  granular  sub- 
stance within  the  cell.  As  in  the  secondary  piles  of  Bitter,  which,  when 


ANATOMICAL  AND  ELECTRICAL  EXAMINATION.  277 

brought  into  contact  with  an  active  voltaic  circle,  participate  Analofr   with 
in  all  its  qualities,  physiological  and  chemical,  give  shocks,  the  secondary 
produce  decompositions,  and  continue  to  do  so  for  a  time  aft-  plles  of  Rltter- 
er  the  original  influence  has  ceased,  so  a  similar  conservation  occurs  in  the 
interior  of  the  vesicle ;  and  this  I  consider  to  "be  the  consequence  of  the 
difference  of  structure  of  the  fibrous  axis  cylinder  and  the  granular  vesi- 
cle contents.     The  continuous  lines  along  which  the  influence  has  been 
coming  terminate  on  reaching  the  vesicle,  and  are  replaced  by  a  divided 
and  inferior  conveying  structure,  a  structure  which  recalls  at  once  the  sec- 
ondary piles  of  Hitter  just  alluded  to. 

We  may  therefore  truly  say  that  these  electrical  experiments  offer  a 
striking  confirmation  of  the  truth  of  the  conclusions  to  Coincidence  of 
which  we  have  come  from  the  study  of  the  anatomical  struc-  anelectrical 
ture  of  a  nervous  arc.  They  assure  us  that  a  vesicle,  and  examination, 
therefore  a  ganglion,  has  a  double  office  to  perform,  the  stopping,  reserv- 
ing, storing  up  a  part  of  the  influence  which  is  brought  to  it,  and  also 
the  conveying  of  that  incident  influence  into  many  new  channels.  These 
conclusions  are  altogether  independent  of  any  conception  of  the  nature  of 
the  nervous  agent :  it  may  be  identical  with,  or  allied  to,  electricity,  or  it 
may  be  a  totally  different  principle.  It  is  not  that  question  which  we 
are  concerning  ourselves  with  now.  We  are  dealing  with  structure  and 
its  interpretation.  Whatever  our  views  may  be  of  the  nature  of  inner  va- 
tion,  we  shall  find  ourselves  constrained  to  infer  that  the  delays,  diver- 
gences, detentions,  and  subsequent  surrender,  the  opportunity  of  diverg- 
ing from  one  into  many  new  channels,  or  conversely  the  convergence  fro  in 
many  lines  of  entry  into  a  single  one  of  exit,  with  all  the  accompanying 
interferences  and  reactions,  must  be  common  to  both  the  electrical  and 
the  nervous  agent,  for  they  depend,  not  upon  the  qualities  of  those  prin- 
ciples, but  upon  the  anatomical  structure  through  which  they  are  passing. 
With  these  remarks  I  proceed  to  an  exposition  of  the  typical  construc- 
tion of  the  nervous  system,  pointing  out  its  successive  com-  Hypothetical 
plications.  The  hypothetical  diagrams  which  I  shall  now  SS2^2*2 
present  are  chiefly  for  the  sake  of  impressing  the  conclu-  anism. 
sions  at  which  we  have  arrived  from  a  consideration  of  the  structure  of 
the  nervous  elements,  fibrous  and  vesicular,  the  experimental  determina- 
tion of  those  functions,  and  their  electrical  phenomena.  That  these  dia- 
grams  are,  however,  somewhat  more  than  imaginary 
sketches,  will  be  obvious  from  a  consideration  of  the 
nervous  mechanism  of  the  articulata,  which  offers 
striking  illustrations  of  them. 

The  simple  automatic  nerve  arc,  Fig.  122,  consists 
of  an  afferent  or  centripetal  fibre,  #,  connected  contin- 
uously  with  an  efferent  or  centrifugal  fibre,  e.  An 


278 


SIMPLE   AND   MULTIPLE   ARCS. 


impression  made  on  the  free  extremity  of  a  instantly  produces  a  con- 
Fia  128.  traction  in  the  muscular  fibre  m,  which  the  effe- 

rent branch  e  supplies.     The  whole  force  is  at 
once  consumed,  no  portion  of  it  remaining. 

The  simple  cellated  nerve  arc,  Fig.  123,  con- 
sists of  a  centripetal  fibre,  <z,  which,  receiving 
impressions  on  its  free  extremity,  conveys  them 
to  the  vesicle  v,  from  which  the  influence  passes 
forward  along  the  centrifugal  fibre  6,  causing  the 
simple  ceiiated  arc.  muscular  fibre  m,  which  the  nerve  supplies,  to 

contract.  An  impression  made  at  a  therefore  produces  motion  at  m. 
The  action  is  purely  automatic,  and  a  part  of  the  force  is  stored  up  or 
remains  in  the  vesicle. 

In  the  figures  here  given,  the  centripetal  and  centrifugal  fibres  are  rep- 
resented apart.  In  fact,  however,  they  may  be  considered  as  bound  to- 
gether, for  the  sake  of  compactness,  without  there  being  any  fusion  or 
coalescence  of  structure  or  functions.  It  is  also  to  be  understood  that 
the  free  extremity  of  the  centripetal  fibre  is  connected  with  some  special 
mechanism  adapted  to  the  influence  it  is  to  receive.  Thus  its  axis  cyl- 
inder may  be  naked,  or  connected  with  a  vesicle,  or  with  an  apparatus 
for  the  reception  of  light,  or  sound,  or  heat,  or  pressure,  &c. 

Multiple  automatic  nerve  arcs  arise  from  an  arrangement  of  many  such 
simple  arcs  in  succession  longitudinally,  as  in  Fig. 
124,  or  it  may  be  in  a  circular  order.  The  former 
case  is  presented  in  the  articulata,  the  latter  in  the  ra- 
diata.  Each  symmetrical  portion  of  the  animal  has 
its  own  nervous  arc,  but  as  such  symmetrical  portions 
are  not  destined  to  live  an  independent  life,  but  to  act 
in  unison  with  the  others,  a  necessity  arises  for  each 
arc  to  be  brought  in  relation  and  maintain  a  connec- 
tion with  the  others,  and  this  is  done  by  extending 
from  ganglion  to  ganglion  fibres  of  communication,  <?,  <?,  which  may  here 
Commissurai  be  called  commissural  fibres.  So  the  circle  of  ganglia  which 
fibres.  surrounds  the  mouth  of  the  radiata  is  not  a  circular  arrange- 

ment of  isolated  ganglia,  but  a  ring  of  ganglia  and  commissures  conjoint- 
ly. Where  the  nervous  system  is  planned  symmetrically  on  the  two 
sides  of  the  mesial  plane,  the  ganglia  are  commissured  across  the  plane 
to  insure  a  reciprocity  of  action.  In  the  molluscs,  whose  organs  of  ani- 
mal life  show  this  bilateral  symmetry,  and  which  have  three  such  gan- 
glia, the  cephalic,  pedal,  and  parieto-splanchnic,  each  is  commissured  with 
its  colleague  on  the  other  side  of  the  plane,  or  they  are  brought  up  to  the 
plane  and  juxtaposed,  the  commissure  then  disappearing,  but  their  bi- 
lobed  aspect  betraying  their  separate  construction.  The  coalescence  fre- 


Fig.  124. 


Multiple  nerve  arcs. 


COMMISSURAL  ACTION. 


279 


Fig.  125. 


Pairs  of  arcs  commissure*. 


quently  becomes  more  intimate,  and  all  traces  of  the 
original  double  construction  disappear. 

The  letters  remaining  the  same  as  in  the  preced- 
ing diagrams,  Fig.  125  represents  the  manner  of 
commissuring  across  the  mesial  plane. 

As  illustrations  of  the  manner  in  which  these 
mechanical  principles  are  carried  out,  the  following 


Fig.  12T. 


Fig.  i2s. 


Fig.  126,  nervous  system  of  the  larva  of  the  sphinx  li- 
gustri,  showing  the  successive  arrangement  of  mul-  IU   trations 
tiple  nerve-arcs  from  1  to  11,  commissured  with  from  various 
one  another,  and  all  with  the  cephalic  ganglion  animals- 
17,  which  is  their  common  register. 

Fig.  127,  the  pupa  condition  of 
the  same  insect,  and  Fig.  128  the 
imago.  (Newport.) 

Fig.  129,  nervous  system  of  the 
asterias,  in  its  elementary  parts. 
It  consists  of  a  series  of  five  gan- 
glia, gr,  g,  circularly  arranged  round 

Fig.  129. 


I 

Nervous  system  Nervous  system  of  Nervous  system  of 
of  larva  of  pupa  of  sphinx  li-   imago  of  sphinx  li- 

sphinx  ligustri.    gustri.  gustri. 

the  mouth  of  the  animal,  and  giving  forth 
to  each  ray  a  pair  of  nerves.  (Tiedemann.) 
Fig.  130,  nervous  system 
of  patella :  Z,  Z,  lateral  ganglia, 
commissured  with  the  cephal- 
ic, which  is  between  them  ;  t, 
the  transverse  or'subossopha- 
system  of  geal  ganglion,  commissured  in 
patella-  like  manner.  (Cuvier.) 

Fig.  131,  nervous  system  of  sepia  octo- 
pus :  C9  cephalic  ganglion ;  0,  0,  optic  gan- 
glia ;  <?,  suboesophageal  ganglion ;  19  Z,  lat- 
eral stellate  ganglia ;  a,  abdominal  or  vis- 
ceral ganglion.  (Cuvier.) 


Nervous  system  of  asterias. 
Fig.  131. 


Nervous  system  of  octopus. 


280 


COMMISSUEAL   ACTION. 


Fig.  132,  nervous  system  of  aplysia :  a,  an- 
terior ganglion  ;  c,  cephalic  ;  I,  I,  lateral ;  g, 
abdominal. 

In  the  mechanical  interpretation  of  the  nerv- 
Function  of  ous  system,  the  action  of  commis- 
commissures.  SUral  strands  is  a  point  of  primary 
importance.  It  may  Ibe  said  that  they  are  for 
the  purpose  of  drawing  off  from  the  nerve  arc  a 
part  of  the  influence  which  is  coming  along  the 
centripetal  fibre,  and  directing  it  into  a  new  chan- 
nel. If  such  coarse  illustrations  are  permissi- 
ble, the  vesicles  act  like  a  three-way  cock,  or 
perhaps  like  a  piece  of  looking-glass  with  a 

part  of  the  foil  removed  from  its  midst;  a  Nervous  system  of  apiysia. 
beam  of  light  impinging  upon  it  is  in  part  reflected,  and  part  escapes  be- 
hind through  the  uncovered  space.  Though  I  have  described  the  simple 
cellated  nerve  arc  as  containing  essentially  a  ganglion  or  vesicle,  it  is  not 
to  be  supposed  that  such  a  structure  necessarily  impresses  any  change 
on  the  incoming  influence.  Since,  if  we  irritate  a  centripetal  fibre,  mus- 
cular motion  may  ensue  from  propagation  of  that  irritation  through  the 
ganglion,  and  if  we  irritate  a  centrifugal  fibre,  muscular  motion  equally 
ensues,  it  is  quite  clear  that  in  the  so-called  action  of  reflection  by  the 
ganglion  there  is,  in  reality,  no  change  in  the  influence  which  has  been 
brought  along  the  centripetal  fibre.  The  same  impression  on  any  part 
of  the  nervous  arc,  no  matter  on  which  side  of  the  ganglion  it  may  be 
made,  will  produce  the  same  muscular  result. 

Such  considerations  therefore  lead  us  to  suspect  that  nothing  takes 
Actofreflec-  place  in  the  ganglion  which  justifies  such  an  expression  as 
don.  uact  of  reflexion"  or  "reflex  action,"  terms  which  convey  an 

idea  that  the  influence  which  passes  in  the  two  branches  of  the  nerve 
arc  is  different,  the  difference  having  been  established  or  brought  on  by 
the  ganglion.  They  confirm  the  opinion  that  the  ganglion  has,  for  one  of 
its  primary  duties,  the  function  of  permitting  an  escape  of  the  influence 
passing  in  the  interior  of  the  centripetal  fibre  into  new  channels  for  the 
establishment  of  new  results. 

In  the  simple  automatic  nerve  arc  the  impression  and  the  effect  are  in- 
instantaneous  stantaneous.  An  irritation  of  the  centripetal  branch  pro- 
action  of  the  duces,  without  any  sensible  interval  of  time,  muscular  con- 
traction through  the  action  of  the  centrifugal  branch,  and  that 
contraction  ceases  the  moment  the  impression  is  over.  But  the  open- 
Reserved  action  ing  out  of  the  nerve  arcs  by  the  introduction  of  a  vesicle 
of  cellated  arcs,  permits  a  part  of  the  influence,  whatever  it  may  be,  to  be 
drawn  off,  and  this,  now  passing  along  the  commissural  line,  may  be  dis- 


REGISTERING   NERVE  ARC. 


281 


posed  of  in  two  different  ways :  1st.  The  influence  thus  drawn  off  may 
be  instantaneously  consumed  or  utilized  by  exciting,  through  adjacent 
simple  arcs,  synchronous  movements ;  or,  2d.  It  may  be  held  in  reserve 
for  future  use  by  being  carried  along  the  commissure  to  a  receiving,  or, 
as  I  may  term  it,  registering  ganglion. 

This,  therefore,  introduces  a  more  complex  mechanism,  which  may  be 
designated  as, 

The  registering  nerve  arc,  the  typical  construction  of  which  is  repre- 
133.  sented  in  Fig.  133.     In  this  we  have  the    Registering 

centripetal,  a,  and  centrifugal  fibre,  6,  as  be-  nerve  arcs- 
fore,  in  connection  with  their  central  vesicle,  v  ;  but, 
passing  from  that  central  vesicle,  a  commissural  fibre, 
c,  offers  a  channel  of  escape  of  a  part  of  the  influence 
which  so  reaches  the  registering  ganglion,  r,  and  makes 
a  permanent  impression  upon  it  by  disturbing  its  con- 
dition physically  or  chemically;  and,  since  many  nerv- 
ous arcs  may  be  thus  commissured  upon  the  same  registering  ganglion,  it 
thus  becomes  for  them  all  a  central  point  of  deposit  and  a  centre  of  com- 
mon action.  And  in  this  manner  not  only  is  a  temporary  Variable  ef- 
influence  converted  into  a  permanent  impression,  but,  from  fectsansefrom 

x        _  invariable  im- 

the  interaction  of  such  impressions  upon  one  another,  new  pressions. 
and  variable  results  arise.     Some  illustrations  were  given  a  few  pages 
back  of  the  development  of  the  variable  from  the  invariable  in  the  case 
of  certain  ordinary  physical  phenomena,  and  these  may  be  profitably  re- 
ferred to  again. 

A  modification  of  the  registering  nerve  arc  is  presented  in  Fig.  134, 
Fig.  is*,  which  exhibits  the  suppression  of  the  centrifugal  gu  ression  of 
branch,  the  whole  influence  received  passing  along  centrifugal 
the  commissural  line  to  the  registering  ganglion.  branch- 
This  condition  of  things  may  occur  when  the  centripetal  branch 
at  its  free  extremity  is  involved  in  a  mechanism  of  special 
sense,  olfactive,  ophthalmic,  or  auditory.  No  part  of  the  im- 
pression thus  received  is  necessarily  expended  at  once ;  the 
whole  may  be  thus  retained,  and  utilized  at  a  future  time, 
gai  branch.  The  introduction  of  the  registering  ganglion  is  thus  the  in- 
troduction of  the  element  of  time  in  a  living  mechanism.  In  the  lower 
forms  of  arc  an  impression  is  instantaneously  expended,  in  this  it  is  pre- 
served. 

The  common  centre  or  register  of  whatever  impressions  have  been  re- 
ceived by  the  special  sense  instruments,  olfactive,  ophthalmic,  or  auditory, 
as  well  as  impressions  of  a  general  tactile  kind,  is  doubtless 
to  be  properly  regarded  as  the  sensorium.  Though  animals 
constituted  on  this  type  accomplish  many  variable  actions,  that  variabil- 


suppresson 

of  centrifu- 


282  THE   INFLUENTIAL   AEG. 

ity  is  essentially  and  purely  automatic.  As  such  may  be  regarded  the 
instinctive  actions  of  bees,  any  two  of  which,  if  placed  under  the  same 
circumstances,  act  with  undeviating  certainty  in  the  same  way.  The 
whole  career  of  life  of  one  of  these  insects  is  the  whole  career  of  any  oth- 
er. They  build  their  combs  now  in  the  same  way  that  they  did  a  thou- 
sand years  ago ;  their  daily  doings  are  the  same  as  they  have  ever  been. 
Except  as  repccts  a  particular,  hereafter  to  be  pointed  out,  they  may  be 
regarded  as  automatons. 

The  introduction  of  a  registering  ganglion  necessarily  gives  rise  to  an 
Effect  of  the  in-  extension  of  the  physical  relations  of  an  animal  by  connect- 
regisUtCerhTg0f  *  ™&  its  Present  existence  with  antecedent  facts,  for  the  gan- 
gangiion.  glion  at  any  moment  contains  the  relics  of  all  the  impres- 
sions that  have  been  made  on  it  up  to  that  time,  and  these  exert  their  in- 
fluence on  any  action  it  is  about  to  set  up.  In  virtue  of  them,  the  nerv- 
ous mechanism  has  now  the  power  of  modifying  whatever  impressions 
may  be  made  on  its  centripetal  nerves,  and,  within  certain  limits,  of  con- 
verting them  into  different  results.  Yet  still  the  automatic  condition  is 
none  the  less  distinct,  and  still  the  immediate  source  of  every  action  is  to 
be  found  in  external  impressions. 

An  increasing  complexity  of  nervous  structure  is  next  evidenced  by  a 
Sensory  and  division  of  the  registering  ganglion  into  two  portions,  which, 
motor  lobes.  wjtjj  some  incorrectness,  may  be  designated  sensory  and  mo- 
tor lobes,  a  division  which  is  preparatory  to,  and,  indeed,  obviously  con- 
nected with,  the  introduction  of  a  totally  new  method  of  action  and  source 
of  power. 

In  Fig.  135  we  have  an  ideal  sketch  of  this  new  condition  of  things. 
Fig  135  '^ne  letters  used  in  the  preceding  cases,  in  this  refer  again 
to  the  same  parts.  But  now  it  is  seen  in  addition  that 
the  registering  ganglion  has  assumed  a  bilobed  aspect, 
s  ra,  the  letters  respectively  indicating  its  sensory  and  mo- 
tor portions,  or,  to  use  the  language  of  human  anatomy,  a 
thalamus  and  corpus  striatum.  From  these  there  branch 
off  commissural  lines,  radiating  to  a  hemispherical  collec- 
tion of  vesicular  matter,  c  c,  the  representative  of  a  cere- 
brum. 

Assuming  the  registering  ganglion  as  a  centre,  the  arc- 
like  arrangement  on  either  side  of  it  is  symmetrical,  as  is  shown  in  Fig. 
Theinfluen-  135.  And  since  it  will  facilitate  our  consideration  to  intro- 
tiai  arc.  ^uce  ^.g  distinctive  terms,  I  shall  designate  the  external  arc, 
which  is  in  relation  with  the  external  world,  as  the  automatic  arc,  and 
the  inner  one,  which  is  in  relation  with  the  cerebrum,  the  influential  arc. 
Throughout  this  work  I  have  constantly  assumed  the  existence  of  an 
intellectual  principle,  spirit,  or  soul,  whose  links  of  connection  with  the 


OF  THE  EXISTENCE   OF  THE   SOUL.  283 

external  world  are  the  sensory  ganglia  and  the  cerebral  Evidence  of  the 
hemispheres.     We  may  now  profitably  inquire  whether  any  existence  of  the 

j.   •      -u  i,   if     f  ^  £         t.  soul  derived 

argument  in  behalf  of  the  existence  of  such  an  agent  may  fr0m  cerebral 
be  gathered  from  the  anatomical  and  physiological  facts  just  structure- 
presented,  or  whether  we  must  assume  it  as  a  postulate,  relying  for  proof 
on  evidences  of  a  totally  different  character  to  those  which  are  presented 
by  the  science  now  engaging  our  attention.  It  is  to  be  greatly  regretted 
that  evidence  drawn  from  structural  arrangement  has  hitherto,  by  very 
high  authority,  either  been  totally  cast  aside  or  held  in  very  light  esteem. 
It  is  still  more  deeply  to  be  regretted  that  those  who  should  have  known 
better  have  conceded  the  argument  that  from  no  consideration  based 
upon  anatomical  or  structural  arrangement  could  proof  be  obtained  of 
the  existence  of  an  immaterial  principle.  Even  by  such,  the  study  of 
physiology  has  been  designated  as  leading  to  materialism,  and,  with  an 
injustice  which  can  not  be  too  emphatically  reprobated,  the  scandal  has 
often  been  quoted,  that  where  there  are  three  physicians  there  are  two 
atheists. 

But  what  if  it  should  turn  out  that,  from  the  study  of  the  cerebral 
mechanism,  distinct  proof  can  be  obtained  on  this  point — proof  of  just  as 
cogent  a  nature  in  support  of  the  doctrine  of  the  existence  of  the  soul 
as  that  which  we  have  of  the  existence  of  the  external  world,  and  of  pre- 
cisely the  same  character?  Without,  therefore,  occupying -myself  with 
such  other  evidence  as  might  be  drawn  from  theological  or  metaphysical 
sources,  and  which  are  therefore  extraneous  to  the  object  of  this  work,  I 
shall  proceed  to  point  out  such  considerations  as  naturally  offer  them- 
selves to  our  minds  when  we  recall  the  general  structure  of  the  nervous 
apparatus.  Eepeating,  therefore,  such  facts  as  may  be  necessary  for  the 
proper  understanding  of  this  interesting  argument,  I  present  it  as  follows : 

The  simple  cellated  nervous  arc  consists  essentially  of  these  portions, 
a  centripetal  fibre,  a  vesicle,  and  a  centrifugal  fibre ;  the  cen-  Automatic 
tripetal  fibre  may  have  at  its  outward  or  receiving  extremity  mechanism  of 
vesicular  or  cellular  material.  Thus  constituted,  this  mech- 
anism is  ready  to  receive  external  impressions,  which,  if  such  language 
may  be  appropriately  used,  are  converted  or  reflected  in  part  by  the  gan- 
glion into  motions,  and  the  residue  retained.  But  the  arc,  viewed  by  it- 
self, is  a  mere  instrument,  ready,  it  is  true,  for  action,  but  possessing  no 
interior  power  of  its  own.  It  is  as  automatic  as  any  mechanical  con- 
trivance in  which,  before  a  given  motion  can  be  made,  a  certain  spring 
must  be  touched. 

The  essential  condition  of  the  activity  of  such  a  nervous  arc  is  there- 
fore the  presence  and  influence  of  an  external  agent — a  some-  Re  uireg  an 
thing  which  can  commence  the  primitive  impression,  for  with-  external  agent 
out  it  the  mechanism  can  display  no  kind  of  result.     More-  for  actlon* 


2k*  INVERSE  PHYSIOLOGICAL  PROBLEMS. 

over,  there  must  be  an  adaptation  between  the  nature  of  that  agent  and 
the  structure  thus  brought  in  relation  with  it,  as  is  strikingly  illustrated 
by  each  of  the  organs  of  sense.  Thus  the  peripheral  extremities  of  the 
fibrils  of  the  optic  nerve  are  involved  in  a  combination  of  a  purely  phys- 
ical kind,  having  relation  to  the  properties  of  light :  the  convex  surface 
of  the  cornea,  the  unequicurved  lens,  the  diaphragmatic  iris,  the  interior 
investiture  of  black  pigment,  these  are  all  structures  the  object  of  which 
we  clearly  understand.  We  know  that  the  rays  of  light  must  undergo 
refraction  at  the  curved  surfaces  upon  which  they  are  incident,  and  de- 
pict the  images  of  external  forms  on  the  retina  or  black  pigment,  the  iris 
expanding  or  contracting,  as  the  case  may  be,  to  regulate  the  entrance  of 
Adaptation  be-  the  light.  So  completely  do  we  admit  this  principle  of  an 
!*  adaptation  of  structure  to  the  nature  of  the  agent  which  is 
to  set  it  in  activity,  that  in  this  particular  instance,  without 
any  hesitation,  we  class  the  eye  among  optical  instruments,  and  include 
its  description  in  our  optical  treatises.  But  in  the  same  manner  that, 
starting  from  the  well-known  properties  of  light,  we  advance  to  the  ex- 
planation of  the  uses  of  each  of  the  various  parts  of  the  eye,  there  can  be 
no  doubt  that  the  converse  of  this  method  of  reasoning  would  be  possi- 
ble to  an  intellect  of  sufficient  power,  who,  from  a  full  consideration  of 
the  structure  of  the  eye,  might  determine  the  properties  of  light,  guided 
in  doing  this  by  the  principle  that  there  must  be  an  adaptation  between 
such  structures  and  such  properties ;  and,  in  the  same  manner,  a  man 
deaf  and  dumb,  but  of  an  intellect  of  great  capacity,  might  doubtless, 
from  the  critical  study  of  the  construction  of  the  ear,  determine  the  na- 
ture of  sounds.  Nay,  even  more,  it  is  not  impossible  that  he  should  be 
able  to  compare  together  the  physical  peculiarity  of  the  movements  which 
constitute  light  or  sound  respectively,  and  to  demonstrate  that  these 
originate  in  normal,  and  those  in  transverse  vibrations. 

So,  therefore,  these  problems  present  themselves  under  a  double  aspect, 
Nature  of  in-  and  are  capable  both  of  a  direct  and  an  inverse  solution : 
Mcaihprob-  Given  *ne  nature  of  light,  to  determine  what  must  necessarily 
lems.  be  the  construction  of  the  organ  of  vision ;  or,  Given  the  con- 

struction of  the  eye,  to  determine  what  is  the  nature  of  light ;  and  the 
same  might  be  said  of  the  organ  of  hearing.  This  inverse  method  of 
treating  natural  agents  is  still  in  its  infancy,  because  of  the  extreme  im- 
perfection of  our  knowledge ;  but  doubtless  what  has  been  said  will  re- 
call to  the  mind  of  the  reader  the  parallel  example  which  is  furnished  by 
astronomy,  and  which,  within  a  few  years  past,  has  yielded  such  a  splen- 
did result.  The  mass  of  a  planet  being  known,  the  perturbations  which 
it  can  cause  in  another  are  capable  of  direct  computation,  but  it  was  re- 
served for  Leverrier  to  discuss  the  inverse  problem,  and  from  the  per- 
turbations to  find  the  place  of  the  planet.  The  discovery  of  Neptune 
was  the  result. 


OF  THE   EXISTENCE   OF  THE  SOUL. 

Now  the  problem  we  are  dealing  with  is  of  this  inverse  kind.  It  may 
be  stated,  Given  the  structure  of  the  cerebrum,  to  determine  the  nature 
of  the  agent  that  sets  it  in  action.  And  herein  the  fact  which  chiefly 
guides  us  is  the  absolute  analogy  in  construction  between  the  elementary 
arrangement  of  the  cerebrum  and  any  other  nervous  arc.  In  it  we  plainly 
recognize  the  centripetal  and  centrifugal  fibres,  and  their  con-  External  influ- 
vergence  to  the  sensory  ganglia,  the  corpus  striatum  and  f^ 
optic  thalamus ;  we  notice  the  vesicular  material  at  their  tial  arc. 
external  periphery  as  presented  in  the  convolutions  of  the  human  brain ; 
and  if  in  other  nervous  arcs  the  structure  is  merely  automatic,  and  can 
display  no  phenomena  of  itself,  but  requires  the  influence  of  an  external 
agent — if  the  optical  apparatus  be  inert  and  without  value  save  under 
the  influences  of  light — if  the  auditory  apparatus  yields  no  result  save 
under  the  impressions  of  sound — since  there  is  between  these  structures 
and  the  elementary  structure  of  the  cerebrum  a  perfect  analogy,  we  are 
entitled  to  come  to  the  same  conclusion  in  this  instance  as  in  those,  and, 
asserting  the  absolute  inertness  of  the  cerebral  structure  in  itself, 
to  impute  the  phenomena  it  displays  to  an  agent  as  perfectly 
external  to  the  body  and  as  independent  of  it  as  are  light  and  sound, 
and  that  agent  is  the  soul. 

It  would  not  comport  with  the  object  of  this  work  to  pursue  this  ar- 
gument in  its  details,  yet  I  can  not  forbear  observing  that,  even  so  far  as 
we  have  already  advanced,  the  point  which,  after  all,  is  of  the  utmost 
importance,  is  completely  attained.  Those  who  have  accused  physiology 
of  tending  toward  materialism  have  never  duly  weighed  the  accusation 
they  make,  and  certainly  have  never  understood  the  nature  of  the  argu- 
ments it  can  present ;  for  such  as  the  one  here  imperfectly  set  forth,  from 
their  tangible  nature,  will  commend  themselves  to  many  minds  who  do 
not  appreciate  the  strength  of  purely  metaphysical  arguments,  and  herein 
they  may  become  subservient  to  the  highest  and  most  enduring  interests 
of  our  race. 

And  thus  it  may  be  proved  that  those  actions  which  we  term  intellectual 
do  not  spring  from  mere  matter  alone,  nor  are  they  functions  Inde  endence 
of  mere  material  combinations  ;  for  though  it  is  indisputably  and  immortal- 
true  that  the  mind  seems  to  grow  with  the  bodily  structure,  lty  °J 
and  declines  with  it,  exhibiting  the  full  perfection  of  its  powers  at  the 
period  of  bodily  maturity,  it  may  be  demonstrated  that  all  this  arises 
from  the  increase,  perfection,  and  diminution  of  the  instrument  through 
which  it  is  working.  An  accomplished  artisan  can  not  display  his  power 
through  an  imperfect  tool,  nor,  if  the  tool  should  be  broken,  or  become 
useless  through  impairment,  is  it  any  proof  that  the  artisan  has  ceased  to 
exist ;  and  so,  though  we  admit  that  there  is  a  correspondence  between 
the  development  of  the  mind  and  the  growth  of  the  body,  we  deny  that 


286  OPINIONS   RESPECTING   THE   SOUL. 

it  follows  from  that,  either  that  the  mind  did  not  pre-exist,  or  that  the 
death  of  the  body  implies  its  annihilation. 

If  it  fell  within  the  compass  of  our  plan,  we  might  proceed  to  consider 
how  far,  since  the  mind  can  act  upon  external  nature  through 

Opinions  re-  f 

specting  the  the  intervention  of  the  bodily  mechanism,  the  converse  is 
soui^ntertain-  P088^6 ;  how,  since  the  face  of  things  around  us  can  be 
ed  by  different  changed  by  our  voluntary  exertions,  the  intellectual  faculties 
may  be  changed  by  the  action  of  external  nature  through  the 
bodily  mechanism.  And  since  we  have  established  the  existence  of  the 
intellectual  principle  as  external  to  the  body,  we  might  proceed,  for  now 
we  are  entitled  so  to  do,  to  reason  respecting  its  nature  from  the  phenom- 
ena it  displays.  I  do  not,  however,  propose  to  enter  on  those  considera- 
tions now,  and  shall  close  these  remarks  with  a  reference  to  some  doc- 
trines proposed  by  the  most  highly-advanced  and  intellectual  portions  of 
the  human  family. 

It  is  said  that  the  spirit  of  man  is  created  in  the  image  of  God,  an  ob- 
servation strikingly  illustrated  by  the  fact  that,  as  regards  both,  two  es- 
sentially different  doctrines  have  been  held — the  pantheistic,  by  some  of 
the  most  highly  advanced  of  the  Asiatics,  and  the  anthropomorphic,  by 
the  Europeans.  The  pantheistic  supposes  the  human  soul  to  be  a  part 
of  the  Deity,  and  therefore  devoid  of  form  ;  the  anthropomorphic  as  hav- 
ing the  likeness  of  the  body.  The  Asiatics,  then,  regarding  the  Deity  as 
a  principle  diffused  in  and  throughout  nature,  consider  the  spirit  of  man 
as  a  part  or  portion  thereof,  and  often  use  such  illustrative  allusions  as 
those  of  a  drop  of  water  in  the  ocean,  a  spark  of  a  universal  and  vital 
flame ;  or,  if  they  do  not  accept  this  view  of  a  oneness  in 'the  nature  of 
spirit  and  Deity,  they  regard  the  former  as  arising  in  some  manner  from 
the  latter,  just  as  waves  may  exist  upon  the  sea,  or  sounds  may  arise  in 
the  air.  They  believe  that  at  death  there  is,  as  it  were,  a  reunion  of  the 
part  with  the  whole,  as  every  drop  of  water  sooner  or  later  finds  its  way 
back  to  the  sea,  or  waves  become  quiet  and  disappear,  or  sounds  die  away 
in  the  air. 

But  with  European  nations  there  has  been,  from  their  very  infancy,  a 
tendency  to  the  anthropomorphic  conception.  The  barbarians  before  the 
Roman  empire,  in  their  legendary  fables,  accepted  the  idea  of  disembod- 
ied spirits  under  the  shape  of  men,  and  through  the  intervening  ages  up 
to  our  own  times,  such  notions,  under  various  forms,  have  been  held. 
The  rural  populations  entertain  an  undoubted  faith  in  fairies  and  ghosts, 
so  that  it  might  be  asserted  that  this  manner  of  viewing  the  thing  is 
almost  natural  to  us.  We  instinctively  represent  to  ourselves  in  this 
way  the  immaterial  principle,  and  in  the  case  of  each  individual  expect  a 
correspondence  between  it  and  his  bodily  form.  Whatever  may  be  our 
authority  for  arriving  at  such  a  conclusion,  there  can  be  no  doubt  that  it 


ORGANS   OF  SPACE  AND 'TIME.  287 

so  specializes  and  intensifies  our  ideas,  and  is  so  connected  with  many 
of  our  most  highly  cherished  recollections,  that,  even  were  the  evidence 
in  its  behalf  far  weaker  than  it  actually  is,  we  should  look  without  favor 
on  any  attempt  to  invalidate  the  doctrine,  and,  if  forced  to  do  so,  should 
abandon  it  with  regret.  The  pantheistic  is  a  grand  but  cold  philosoph- 
ical idea ;  the  anthropomorphic  embodies  our  recollections,  and  restores 
to  us  our  dead.  The  one  is  the  dream  of  the  intellect,  the  other  is  the 
hope  of  the  heart. 

We  have  thus  traced  out  the  essential  elements  of  the  nervous  ma- 
chine in  its  highest  complexity,  and  shown  its  gradual  rise  imperfection 
from  the  purely  automatic  to  the  influential.  We  may  there-  jj 
fore  comprehend  the  difficulties  under  which  metaphysicians  tions. 
labor,  who  confound  all  these  parts  and  all  these  functions  together,  and 
pass  over  as  of  no  account  the  guiding  indications  which  are  furnished 
by  the  study  of  structure.  It  is  not  difficult  for  the  physiologist,  en- 
lightened by  the  knowledge  he  possesses,  to  recognize  the  various  points 
at  which  these  philosophers  go  astray — the  point  at  which  their  theories 
cease  to  be  representations  of  the  truth.  He  acknowledges  the  existence 
of  an  external  nature,  and  equally  the  existence  of  an  immaterial  spirit, 
and  to  their  action  on  or  relation  to  each  other  he  traces  the  resulting 
phenomena.  He  admits  that,  among  certain  classes  of  life,  every  motion 
and  every  sensation  is  due  to  external  nature  alone,  but  to  these  purely 
automatic  groups  man  does  not  belong.  He  repudiates  the  doctrines  of 
the  idealist,  because,  though  they  may  maintain  themselves  in  the  uncer- 
tainties of  metaphysical  argument,  they  are  dissipated  at  once  in  the  more 
severe  trial  of  anatomical  discussion. 

There  are  two  fundamental  ideas  essentially  attached  to  all  our  per- 
ceptions of  external  things:  they  are  SPACE  and  TIME,  and  Pro  vision  in  the 
for  these  an  early  provision  is  made  in  the  nervous  mechan-  ^^^lftfim 
ism,  while  yet  it  is  in  an  almost  rudimentary  state.  The  space  and  time. 
development  of  the  eye  and  the  ear,  as  we  shall  more  particularly  find 
when  we  come  to  the  description  of  these  organs,  is  for  this  purpose.  In 
a  philosophical  respect  the  eye  is  the  organ  of  space,  and  the  ear  of  time ; 
the  perceptions  of  which,  by  the  elaborate  mechanism  of  these  structures, 
become  infinitely  more  precise  than  would  be  possible  if  the  sense  of 
touch  alone  were  resorted  to.  The  indications  thus  gathered  are  trans- 
mitted by  the  optic  and  auditory  nerves  respectively  to  the  brain. 

In  its  highest  condition  of  development,  the  nervous  mechanism  has  a 
threefold   operation,  objective,  subjective,  and  impersonal.  Objective,  sub- 
Objective  ideas  arise  in  external  facts ;  subjective  in  register-  fatler&maio 
ed  impressions ;  the  impersonal,  as,  for  example,  the  abstract  erations. 
truths  of  geometry,  issue  of  pure  reason,  and  are  therefore  to  be  attrib- 
uted to  the  essential  nature  of  the  soul.     Of  these  three  elementary  con- 
stituents all  human  knowledge  consists. 


288  VESTIGES   OF   GANGLIONIC   IMPRESSIONS. 

As  respects  subjective  or  registered  impressions,  a  few  remarks  may 
be  here  made.     There  can  not  be  a  doubt  that  the  registry 

Illustrations  of  / 

the  vestiges  of  of  impressions  involves  an  actual  structural  change  in  the 
impressions.  ganglion,  which  is  of  a  permanent  character.  These  changes 
may  be  rudely  and  imperfectly  illustrated  by  experiments,  such  as  I  pub- 
lished years  ago,  of  which  the  following  may  be  taken  as  examples  :  If, 
on  a  cold,  polished  piece  of  metal,  any  object,  as  a  wafer,  is  laid,  and  the 
metal  then  be  breathed  upon,  and,  when  the  moisture  has  had  time  to 
disappear,  the  wafer  be  thrown  ofT,  though  now  upon  the  polished  surface 
the  most  critical  inspection  can  discover  no  trace  of  any  form,  if  we 
breathe  upon  it  a  spectral  figure  of  the  wafer  comes  into  view,  and  this 
may  be  done  again  and  again.  Nay,  even  more ;  if  the  polished  metal  be 
carefully  put  aside  where  nothing  can  deteriorate  its  surface,  and  be  so 
kept  for  many  months  (I  have  witnessed  it  even  after  a  year),  on  breath- 
ing again  upon  it,  the  shadowy  form  emerges  ;  or,  if  a  sheet  of  paper  on 
which  a  key  or  other  object  is  laid  be  carried  for  a  few  moments  into  the 
sunshine,  and  then  instantaneously  viewed  in  the  dark,  the  key  being 
simultaneously  removed,  a  fading  spectre  of  the  key  on  the  paper  will  be 
seen ;  and  if  the  paper  be  put  away  where  nothing  can  disturb  it,  and 
so  kept  for  many  months,  at  the  end  thereof,  if  it  be  carried  into  a  dark 
place  and  laid  on  a  piece  of  hot  metal,  the  spectre  of  the  key  will  come 
forth.  In  the  case  of  bodies  more  highly  phosphorescent  than  paper,  the 
spectres  of  many  different  objects  which  may  have  been  in  succession 
laid  originally  thereupon  will,  on  warming,  emerge  in  their  proper  order. 
I  introduce  these  illustrations  for  the  purpose  of  showing  how  trivial 
are  the  impressions  which  may  be  thus  registered  and  preserved.  In- 
deed, I  believe  that  a  shadow  never  falls  upon  a  wall  without  leaving 
thereupon  its  permanent  trace — a  trace  which  might  be  made  visible  by 
resorting  to  proper  processes.  All  kinds  of  photographic  drawing  are  in 
their  degree  examples  of  the  kind.  Of  the  moral  consequences  of  such 
facts  it  is  not  my  object  here  to  speak.  The  world  would  be  none  the 
worse  if  every  secret  action  might  thus  be  made  plain.  But  if  on  such 
inorganic  surfaces  impressions  may  in  this  way  be  preserved,  how  much 
more  likely  is  it  that  the  same  thing  occurs  in  the  purposely-constituted 
ganglion !  Not  that  there  is  any  necessary  coincidence  between  an  ex- 
ternal form  and  its  ganglionic  impression  any  more  than  there  is  be- 
tween the  letters  of  a  message  delivered  in  a  telegraphic  office  and  the  sig- 
interpretation  na^s  wnicn  tne  telegraph  gives  to  the  distant  station,  yet  these 
ofsuchves-  signals  are  easily  retranslated  into  the  original  words — no 
more  than  there  is  between  the  letters  of  a  printed  page  and 
the  acts  or  scenes  they  may  chance  to  describe,  but  those  letters  call  up 
with  clearness  in  the  mind  of  the  reader  the  events  and  scenes.  Indeed, 
the  quickness  with  which  the  mind  interprets  such  traces  or  impressions 


SPONTANEOUS  FUNCTIONS  OF   GANGLIA.  289 

in  its  registering  ganglia  is  illustrated  by  the  rapidity  with  which  we 
gather  the  sense  of  a  printed  page  without  individualizing  each  of  the 
letters  it  contains,  or  as  a  skillful  accountant  runs  his  jeye  over  a  long 
column  of  figures,  and  seems  to  come  by  intuition  at  once  to  the  correct 
sum.  The  capability  which  we  thus  possess  of  determining  a  final  per- 
ception or  judgment  of  results,  without  dwelling  on  the  intermediate 
traces  or  steps,  is  also  illustrated  by  our  appreciation  of  music  without 
concentrating  our  thoughts  on  the  time  and  intensities  of  vibration  or  in- 
terferences of  the  notes,  though  these  mathematical  relations  are  at  the 
very  bottom  of  the  harmony ;  and  conspicuously  does  the  Supreme  In- 
telligence, God,  reach  with  unerring  truth  to  every  final  result  without 
any  necessary  concern  in  the  intermediate  steps. 

From  the  preceding  considerations  we  may  infer  that  there  is  a  neces- 
sary limitation  of  the  amount  of  impressions  capable  of  being  Finite  nature 
registered  in  the  organism,  and  therefore,  in  this  regard,  all  of  human 
human  knowledge  is  finite.     Yet  its  term  is  much  farther  off  kn<mle(Jge- 
than  might  at  first  sight  appear.     A  library  of  a  given  size  may  only  be 
able  to  contain  a  given  number  of  books  upon  its  shelves,  but  the  amount 
of  information  it  is  capable  of  containing  may  be  made  to  vary  with  the 
condensation  and  perspicuity  of  the  books.     /. 

In  the  hypothetical  language  of  physiology,  the  nervous  centres  are 
spoken  of  as  the  origin  of  the  nervous  influence  or  force.  A  conclusion  re- 
close  examination  of  the  phenomena  they  display  leads  us,  specting  the 
however,  to  receive  such  a  doctrine  with  a  certain  amount  function  of 
of  limitation.  Most  of  the  ganglia  produce  no  motor  im-  sanslia- 
pulses  except  under  the  action  of  external  impression,  and  under  the  el- 
ementary view  we  have  just  presented  regarding  the  function  of  the 
brain,  the  same  remark  applies  even  to  it,  since  the  immaterial  principle, 
whose  instrument  it  is,  must  be  regarded  as  an  agent  distinct  from  it, 
and  in  that  respect  external.  Indeed,  the  cases  in  which  the  nervous 
centres  seem  to  display  the  quality  of  spontaneously  originating  force  are 
so  few,  and  in  their  nature  so  doubtful,  that  we  are  almost  entitled  to  dis- 
regard them.  For  example,  the  ganglia  of  the  heart  are  by  some  sup- 
posed to  cause,  by  their  own  inherent  power,  the  contractions  of  that  or- 
gan, which  in  cold-blooded  animals,  long  after  it  has  been  excised,  will 
continue  its  rhythmic  motions.  But  it  is  far  more  agreeable  to  the  anal- 
ogies of  the  nervous  system  to  regard  these  cardiac  ganglia,  not  as  orig- 
inators of  power,  but  as  merely  depositories,  reservoirs,  or  magazines  of 
it.  There  is  nothing  more  extraordinary  in  then:  ability  to  keep  up  the 
motions  of  the  organ  with  which  they  are  connected  than  there  is  in  the 
subsidiary  spring  of  a  chronometer,  which  maintains  the  movement  of 
that  instrument  for  the  period  during  which  the  action  of  the  mainspring 
is  taken  off  while  it  is  being  wound  up.  Yet  the  mainspring,  and  the 

T 


290  MENTAL   EMOTIONS. 

subsidiary  spring  too,  derive  their  mechanical  power  originally  from  the 
force  which  has  wound  up  the  chronometer.  In  this  particular  of  the 
storing  up  of  power  for  its  utilization  in  the  time  of  need,  the  whole  gan- 
glionic  or  sympathetic  system  of  nerves  may  be  taken  as  the  great  ex- 
ample. 

The  conveyance  of  an  impression  through  the  great  nervous  centres  is 
more  complicated  than  it  is  through  the  nerve  trunks.     It 

Nature  of  the  r  ••./.<.       «•   •         • 

action  of  nerve  may  be  conducted,  ii  oi  sufficient  intensity,  through  one  gan- 
res'  glion  after  another  in  succession.     The  intermedium  through 

which  this  is  done  is  probably  the  nerve-tubes  in  a  majority  of  instances, 
though  perhaps,  in  those  cases  in  which  a  longer  period  of  time  is  occu- 
pied, it  may  be  rather  from  vesicle  to  vesicle  than  through  the  tubes. 
Impressions  may  be  thus  transferred  from  one  set  of  tubes  to  others,  or 
Conveyance  of  they  may  be  diffused  from  a  nerve  centre  to  many  tubes 
IhroughTn-  around»  and  so  produce  a  wider  circle  of  influence.  That 
tres.  transfer  of  impressions  from  centripetal  to  centrifugal  fibres 

which  has  been  previously  described  as  reflex  action,  though  commonly 
involuntary,  may  in  many  instances  be  governed  by  a  direct  exertion  of 
the  will.  Thus  the  respiratory  movements  for  the  introduction  of  air 
may  be  controlled  to  a  certain  extent,  as  in  holding  the  breath,  but  this 
is  only  during  a  short  time,  for  the  necessity  of  permitting  the  normal 
action  to  occur  presently  becomes  insuperable.  Of  reflex  actions,  the 
majority  are  obviously  for  the  accomplishment  of  some  special  object  so 
long  as  the  system  is  in  health — they  are  means  for  an  end ;  but  in  dis- 
eased conditions  they  very  often  occur  in  an  objectless  or  useless  way. 

In  its  most  perfect  condition,  the  nervous  system  thus  consists  of  two 
Nature  of  men-  separate  mechanisms,  the  automatic  and  the  influential,  and 
tai  emotions,  these  are  so  related  that  they  can  mutually  act  on  one  an- 
other. The  will  can  exert  a  control  over  the  so-called  reflecting  func- 
tion of  the  automatic  part,  and  external  impressions  which  have  been 
received  by  that  part  can  exert  a  reaction  upon  the  wilL  It  is  in  this 
way  that  mental  emotions  may  be  explained,  the  power  of  external  influ- 
ences which  antagonize  or  even  overcome  the  will. 


THE   SPINAL  AXIS.  291 


CHAPTER  XV. 

THE  SPINAL  AXIS. 

Primitive  Development  of  Nervous  System. — Itsjinal  Condition  in  different  Vertebrates. 

The  Spinal  Cord:  its  Structure. — Its  Membranes. — Its  Thirty-one  Pairs  of  Nerves. — Proper- 
ties of  their  Hoots. — Functions  of  the  Cord. — Bell's  Discovery. —  Transmission  of  Longitudinal 
and  Transverse  Influences. — Reflex  Action  of  the  Cord. — Nature  of  Reflex  Action. — Motor  and 
Sensory  Tracts  of  the  Cord. — Summary  of  its  Functions.. 

The  Medulla  Oblongata :  its  Structure  and  Functions. 

The  Pons  Varolii:  its  Structure  and  Functions. 

Dr.  Carpenter's  Views  of  the  Analogy  between  tlie  Spinal  Cord  of  Vertebrates  and  the  Ventral 
Cord  of  Articulates. 

WE  now  commence  a  more  detailed  examination  of  the  nervous  sys- 
tem, presenting  a  description  of  its  structure  as  far  as  may  Subdivisions 
be  necessary  for  the  understanding  of  its  functions.  We  of  the  subJ*ect- 
shall  follow  the  usual  division  of  this  subject  as  adopted  by  authors. 
This  will  therefore  lead  us  to  speak  in  succession  of  the  spinal  cord  and 
medulla  oblongata,  of  the  sensory  ganglia,  of  the  cerebellum  and  cere*- 
brum,  of  the  nerves  generally,  and,  lastly,  of  the  sympathetic  system. 

The  important  position  occupied  by  the  nervous  mechanism  in  the  an- 
imal body  will  always  draw  to  it  the  closest  attention  of  the  physiol- 
ogist, and  yet  it  must  be  admitted  that  hitherto  it  is  the  least  ad- 
vanced portion  of  the  science.  If  metaphysicians  are  to  be  blamed  for 
casting  away  the  advantages  which  arise  from  a  study  of  Advantages  de- 
structure,  the  earlier  physiologists  were  almost  equally  in 
error  in  confining  themselves  to  human  anatomy  alone, 
They  did  this  under  an  impression  that  there  is  an  essential  and  intrinsic 
difference  between  the  functions  of  this  system  in  man  and  in  the  lower 
animals. 

There  is  an  analogy  of  construction  in  all  the  forms  of  nervous  system 
presented  by  the  different  animal  tribes,  which,  in  the  infancy  of  the  sci- 
ences of  organization,  was  attributed  to  a  unity  of  design  pervading  the 
plan  of  Nature,  but  which,  when  seen  from  a  higher  and  more  philosoph- 
ical point  of  view,  is  plainly  the  necessary  result  of  a  universal  and  un- 
varying law  of  development.  This  conclusion,  which,  when  better  un- 
derstood, is  doubtless  destined  to  become  one  of  the  most  important  sug- 
gestions ever  furnished  by  science  respecting  the  management  of  the 
world,  is  strikingly  enforced  by  the  analogies  between  the  Advant<>  esde- 
successive  transitory  stages  of  development  of  this  system  rived  from  de- 
at  different  epochs  in  the  life  of  man,  and  the  permanent  vel°Pment- 
form  it  assumes  in  members  of  the  entire  animal  series.  Since  there  can 


292  DEVELOPMENT   OF   THE   CEEEBRO-SPINAL   AXIS. 

be  no  doubt  that  every  animal  function,  from  the  automatic  motions  of 
the  obscurest  living  form  up  to  processes  of  intellection  of  man,  depend 
upon  this  structure  as  on  an  instrument,  we  may,  by  a  due  comparison  of 
the  habits,  instincts,  or  other  phenomena  in  such  cases  with  the  existing 
nervous  development,  arrive  at 'true  conclusions  of  the  connection  between 
its  structure  and  its  functions. :.  We  shall  therefore  indicate,  in  a  general 
manner,  the  order  of  development  of  this  system  in  man,  and  then  its 
permanent  stages  in  the  animaL  series. 

The  nervous  system  first  n:i.kes  its  appearance  in  the  serous  lamina 
Course  of  de-  of  the  germinal  membrane  and  in  the  midst  of  the  pellucid 
veiopment  of  area  ag  ^e  prjmitiye  trace,  a  delicate  and  pale- white  line  ris- 
ous  system,  ing  somewhat  above  the  general  surface  of  the  germinal  area. 
This  line  soon  presents  a  conical' aspect ;  the  thicker  portion  is  destined 
to  become  the  head  of  the  embryo.  After  a  short  interval,  the  membrane 
is  gathered  into  a  fold  on  each  side  of  the  primitive  trace,  and  these  folds, 
advancing  toward  each  other,  constitute  the  dorsal  laminse,  which,  when 
their  edges  have  met  and  coalesced,  form  a  tubular  cavity — a. rudimentary 
preparation  for  the  vertebral  column.  Beneath  the  tube  so  arising  may 
be  discovered,  at  this  stage,  a  line  of  nucleated  cells — the  chorda  dorsalis. 
As  the  edges  of  the  dorsal  laminae  approach  each  other,  they  assume  a  wavy 
form,  and  simultaneously  a  bending  forward  or  curvature  of  the  embryo 
occurs,  so  that  the  vertebral  tube  becomes  arched.  In  the  middle  wavy 
portion  are  now  to  be  seen  rectangular  plates,  the  elements  of  the  future 
vertebras.  The  coalescence  of  the  middle  part  of  the  dorsal  laminas 
takes  place  first,  the  ends  as  yet  diverging  in  the  portions  which  corre- 
spond respectively  to  the  head  and  the  sacrum.  The  spinal  marrow  and 
the  brain  thus  arise  at  the  primitive  trace,  the  brain  being  a  superposed 
or  additional  structure  to  the  spinal  marrow ;  for  now  the  wavy  edges  of 
the  anterior  extremity  are  gradually  seen  to  give  origin  to  three  cells  by 
their  juxtaposition :  1st.  The  epencephalpn,  a  single  cell,  to  produce  the 
medulla  oblongata :  its'  cavity  is  to  be  the  fourth  ventricle ;  2d.  The  mes- 
encephalon,  also  a  single  cell,  for  the  corpora  quadrigemina :  its  cavity 
is  to  be  the  ventricle  of  Sylvius  ;  3d.  The.  deutencephalon,  a  single  cell, 
for  the  optic  thalami :  its  cavity  is  to  be  the  third  ventricle.  Though  at 
first  transparent  and  fluid,  the  nervous  matter  becomes  by  degrees  more 
consistent  and  covered  over  with  a  thin  layer  of  membrane,  the  indica- 
tion of  its  future  investitures.  The  rudiment  of  an  eye,  under  the  form 
of  a  protrusion,  now  appears  from  the  most  anterior  cell ;  and  in  like 
manner  the  auditory  apparatus  emerges  from  the  cell  of  the  medulla  ob- 
longata, from  the  anterior  part  of  which,  by  the  coalescence  of  a  pair  of 
fasciculi  which  have  arisen,  the  cerebellum  begins  to  form.  At  this  peri- 
od, through  the  continued  curvature  of  the  embryo,  the  cell  of  the  cor- 
pora quadrigemina  has  become  most  anterior. 


DEVELOPMENT  OF  THE  CEEEBRO-SPINAL  AXIS.        293 

The  origin  of  the  spinal  cord  and  brain  is  illustrated  in  the  annexed 
figures  from  Bischoff.     Fig.  136  shows  upon  a  dark  ground  Ori  .Q  of  thg 
a  portion  of  the  germinal  membrane,  in  the  midst  of  which  is  spinal  cord  and 
the  area  pellucida  and  primitive  trace :  #,  the  area  pellucida ;  the  bram> 
£,  the  dorsal  laminse ;  c,  the  primitive  trace. 


Fig.  136.  Fig.  137. 


The  primitive  trace,  magnified  8  diameters.  Origin  of  the  brain  upon  the  spinal  cord,  magnified 

8  diameters. 

Fig.  137,  the  same  at  a  later  stage,  preparation  for  the  brain  being 
made.  The  dorsal  Iamina3  are  approaching  each  other,  particularly  to- 
ward the  middle:  «,  the  dilated  upper  extremity  or  cephalic  end,  the 
three  cells  appearing :  the  epencephalon,  mesencephalon,  and  deutenceph- 
alon ;  b,  chorda  dorsalis  along  the  bottom  of  the  groove ;  c,  rudiments  of 
vertebra  ; .  d,  lancet-shaped  dilatation.  In  both  figures  the  pale  borders 
along  the  primitive  trace  are  pellucid  nerve  substance. 

The  dorsal  cord,  which  is  only  a  transitory  structure,  now  disappears, 
the  spinal  marrow  commencing  to  exhibit  a  division  into  four  strands, 
right  and  left,  upper  and  under.  The  medulla  oblongata  flattens  next 
in  its  upper  part,  its  fasciculi  parting  from  each  other;  the  interval  so 
arising  between  them  is  to  be  the  fourth  ventricle.  The  hemispheres 
now  appear  as  a  double  cell,  the  prosencephalon,  and  as  development  goes 
on,  they  soon  exceed  the  corpora  quadrigemina  in  size,  and,  as  they  ad- 
vance, force  these  bodies  backward  and  under  them. 

From  this  it  appears  that  the  type  of  construction  of  the  nervous  sys- 
tem is,  that  upon  the  rudimentary  spinal  marrow  a  series  of  vesicles  is 
developed.  They  constitute  eventually  the  medulla  oblongata,  the  cer- 
ebellum, the  corpora  quadrigemina,  the  thalami  optici,  the  corpora  striata, 
the  olfactive  ganglia,  and  in  front  of  all,  but  destined  to  cover  the  anterior 
portions  over,  the  hemispheres. 

Turning  now  to  the  animal  series,  we  find  in  the  lowest  members  of 


294  THE   SPINAL   COED. 

the  vertebrata,  as  in  the  amphioxus,  the  spinal  cord,  medulla 

Comparative  ' 

nervous  system  oblongata,  and  the  elementary  representatives  of  the  sensory 
in  vertebrates.  gangiia  al0ne,  and  as,  in  succession,  we  pass  to  the  higher 
ones,  we  recognize  a  cerebellum  appearing  over  the  medulla  oblongata, 
and  cerebral  hemispheres  over  the  sensory  ganglia.  These  organs  in 
the  upward  career  become  more  and  more  developed,  the  hemispheres,  for 
example,  soon  equaling  in  size  the  quadrigemina,  and  then  greatly  sur- 
passing them,  and  with  this  increase  of  size  a  higher  grade  of  intelligence 
is  reached.  In  fishes  there  are  four  ganglia,  corresponding  respectively 
to  the  cerebellum,  quadrigemina,  cerebral  hemispheres,  and  olfactive  gan- 
glia. In  reptiles  the  number  of  ganglia  and  their  order  of  occurrence  is 
the  same,  but  the  cerebral  hemispheres  have  now  greatly  increased,  an 
increase  which  is  even  better  marked  in  birds,  for  in  them  the  hem- 
ispheres have  expanded  in  front  so  as  to  cover  the  olfactive  ganglia,  and 
posteriorly  the  optic,  a  condition  of  things  analogous  to  that  presented 
by  the  human  brain  at  about  the  close  of  the  third  month  of  foatal  life, 
and  approaching  that  permanently  exhibited  by  the  lower  mammals,  as, 
for  instance,  the  marsupials.  It  is  to  be  understood  that  what  is  here 
spoken  of  as  the  hemispheres  answers  in  reality  only  to  the  anterior  lobe 
of  the  cerebrum  of  man ;  and  as  in  him,  during  the  fourth  and  fifth  months, 
the  middle  lobes  are  developed  in  the  upward  and  backward  direction 
from  the  anterior,  and  still  later  the  posterior  lobes  from  the  posterior  of 
these,  the  same  course  is  followed  in  the  animal  series,  the  final  type  of 
development,  the  trilobed  cerebrum,  being  only  reached  by  the  highest 
carnivora  and  quadrumanous  animals. 

Commencing  now  more  particularly  with  human  nervous  anatomy — 

STRUCTURE  OF  THE  SPINAL  CORD. 

The  spinal  cord  is  placed  in  the  midst  of  the  vertebral  canal.  In  form 
Description  of  it  is  cylmdroid,  its  section  being  elliptical,  the  lateral  diame- 
the  spinal  cord.  ter  teing  the  long  on^  Longitudinally  it  shows  two  en- 
largements, one  about  its  upper  third,  the  other  toward  its  termination. 
Exteriorly  it  is  white,  but  its  section  shows  a  gray  substance,  arranged 
in  the  form  of  two  crescents  connected  by  an  isthmus.  Above,  it  is  con- 
tinuous with  the  brain,  which,  indeed,  is  a  development  upon  it,  and  be- 
low it  terminates  at  the  cauda  equina.  Its  relative  length  is  much  great- 
er in  foetal  life,  at  the  third  month  of  which  it  extends  into  the  sacrum. 
In  adult  life  it  only  occupies  about  the  upper  two  thirds  of  the  verte- 
bral canal ;  it  is  generally  stated  that  its  termination  is  about  the  first 
or  second  lumbar  vertebra.  Moreover,  it  does  not  fill  the  vertebral  ca- 
nal, being,  by  reason  of  the  transverse  dimensions  of  that  cavity,  rather 
suspended  in  than  confined  by  it.  The  rest  of  the  space,  amount- 
ing to  about  one  third,  is  occupied  by  the  roots  'of  the  nerves,  liga- 


THE  SPINAL  CORD. 


295 


fig.  138. 


The  spinal  cord. 


Fig.  139. 


ments,  the  investitures  of  the  cord,  blood-vessels,  and  a 
liquid. 

Fig.  138,  A,  A,  shows  the  front  view  of  the  spinal 
cord,  with  the  medulla  oblongata ;  B,  B,  the  posterior 
view%;  and  C,  C,  the  decussation  of  its  strands,  from 
which  it  appears  that  the  organ  is  composed  of  two  equi- 
lateral portions.  They  are  united  by  an  interior  com- 
missure, but  separated  in  front  by  the  anterior,  and  be- 
hind by  the  posterior  fissure.  Of  these  the  posterior 
fissure  is  the  deeper,  the  anterior  being  wider.  Besides 
these  regional  divisions,  the  cord  also  presents  longi- 
tudinal furrows,  two  for  each  side,  dividing  it  into  the 
anterior,  the  middle  or  lateral,  and  posterior  columns  or 
tracts,  as  shown  in  the  figures. 

With  respect  to  the  interior  constitution  of  the  cord, 
it  has  already  been  stated  that  it  is  composed  exteriorly 
of  white,  and  interiorly  of  gray  material.     The  relative 
quantities  of  these,  and  the  particular  form  and  distribu- 
tion of  the  gray  substance,  may,  perhaps,  be  best  understood  from  the 

sections  given  in  Fig.  139, 
from  one  to  nineteen,  1  show- 
ing a  transverse  section  as 
high  as  the  cerebral  pedun- 
cles ;  2,  through  the  medulla 
oblongata;  and  the  remaining 
figures,  to  19,  at  lower  and 
lower  points. 

In  the  first  of  these  sec- 
tions, 1  is  the  interpeduncu- 
lar  space ;  2, 2,  inferior  tract ; 
o  9  3,  3,  middle  tract ;  4,  4,  locus 

^H^l     »&*  %.  y/rf^WVr^  ^S^iJ^V  J---*"rrTT'*w 

dl      n     &i    &      10  •      $$•  m&     niger ;  5, 5,  superior  tract ;  6, 

section   of  the   aqueduct   of 
Sylvius ;  7,  7,  section  of  the 
superior  peduncles  of  the  cer- 
ebellum ;  8,  8,  section  of  the 
two  tubercula  quadrigemina. 
In  the  second  section:  1, 1, 
the  pyramidal  bodies;   2,  2, 
olivary    bodies ;    3,  3,  resti- 
form  ;  4,  4,  section  of  middle  strands ;  5,  floor  of  fourth  ventricle. 

In  the  fourth  of  these  sections :  1,  the  right  half  of  the  cord ;  2,  left 
half;  3,  anterior  median  fissure;  4,  posterior  median  fissure;  5,  5,  pos- 


16 


17 


18 


Sections  of  the  spinal  cord. 


296 


STRUCTURE   OF   THE   SPINAL   CORD. 


terior  furrows  :  6,  white  or  anterior  commissure ;  7,  gray  or  posterior 
commissure ;  8,  anterior  horn  of  right  crescent ;  9,  posterior  horn  of  dit- 
to :  it  is  prolonged  to  the  posterior  furrow  ;  10,  antero-lateral  columns ; 
11, 11,  posterior  columns:  these  are  all  of  white  tubular  substance.  The 
symmetrical  reference  numbers  on  one  side  are  omitted  for  the  sake  of 
clearness. 

The  spinal  cord  is  surrounded  by  three  membranes,  continuous  with 
Membranes  of  those  of  the  cranium :  the  dura  mater,  the  arachnoid,  and  the 
the  spinal  cord.  pia  mater.  The  latter  embraces  the  cord  so  closely  as  to  ex- 
ert a  compression  upon  it.  This  is  shown  on  slightly  wounding  it,' when 
the  white  substance  protrudes  through  the  orifice.  Fig.  140. 

Fig.  140 :  1,  spinal  dura  mater  laid  open  and  drawn 
aside ;  2,  2,  sheaths  formed  by  this  membrane  round 
the  roots  and  spinal  ganglia;  3,  spinal  arachnoid; 
4,  4,  sheaths  formed  by  the  arachnoid  around  the 
roots  of  the  nerves  and  dentated  ligament ;  5, 5,  points 
of  communication  of  the  visceral  layer -of  the  arach- 
noid, with  its  parietal  layer ;  6,  pia  mater ;  7,  denta- 
ted ligament  separating  the  anterior  roots  from  the 
posterior  roots  of  the  spinal  nerves,  and  serving  as  a 
communication  between  the  dura  mater  and  pia  mater. 

From  the  spinal  cord  there  arise  thirty-one  pairs 
The  spinal  °f  nerves,  each  nerve  having  two  roots,  an 
nerves.  anterior  or  motor,  and  a  posterior  or  sensory. 

The  anterior  roots  issue  from  the  anterior  furrow, 
Roots  of  the  the  posterior  from  the  posterior  furrow, 
spinal  nerves.  where  the  gray  substance  emerges.  Of 
the  two  the  latter  are  the  larger,  and  have  more  radicles.  They  also 
have,  in  the  intervertebral  foramen,  a  ganglion.  Beyond  the  ganglion  the 
two  roots  coalesce,  and  the  resulting  nerve  trunk,  passing  through  the 
intervertebral  foramen,  divides  into  an  anterior  and  posterior  branch,  for 
the  anterior  and  posterior  portions  of  the  body.  To  this  general  descrip- 
tion there  are,  however,  some  exceptions.  Thus  the  posterior  root  of  the 
first  cervical  nerve  is  smaller  than  the  anterior,  and  very  often  it  has  no 
ganglion.  The  spinal  nerves  are  enumerated  as  eight  cervical,  twelve 
dorsal,  five  lumbar,  and  six  sacral  pairs.  The  cervical  pass  off  to  their 
distribution  transversely,  the  dorsal  obliquely,  and  the  lumbar  and  sacral 
vertically.  The  latter  constitute  the  cauda  equina. 

Fig.  141  illustrates  the  origin  of  the  anterior  roots  of  the  spinal 
nerves.  1,  pons  varolii;  2,  large  and  small  root  of  the  fifth  pair;  3, 
sixth  pair;  4,  facial  nerve;  5,  auditory  nerve;  6,  intermedian  nerve; 
7,  glosso-pharyngeal ;  8,  pneumogastric ;  9,  spinal  accessory ;  10,  hypo- 
glossal. 


Spinal  dura  mater  laid 
open. 


STRUCTURE  OF  THE  SPINAL  CORD. 


297 


Origin  of  anterior 
roots  of  nerves. 


From  11  to  11,  the  eight  anterior  roots  of  the  cervical 
nerves ;  from  12  downward,  the  same  roots  of  the  dorsal 
nerves :  those  of  the  lumbar  and  sacral  are  not  shown  in 
the  figure.  As  at  15,  are  shown  the  anterior  branches  of 
the  spinal  nerves ;  as  at  16,  their  posterior  branches ;  at 
17,  spinal  ganglia  formed  on  the  posterior  roots ;  18,  ante- 
rior roots  cut ;  19,  anterior  roots  cut  beyond  the  ganglion  ; 
20,  dentated  ligament,  separating  anterior  from  posterior 
roots ;  21,  insertion  of  this  ligament  on  dura  mater  by  its 
dentated  edge ;  22,  insertion  of  same  ligament  on  the  pia 
mater. 

Fig.  142  illustrates  the  origin  of  the  posterior  roots  of 
the  spinal  nerves.      1,  tubercnla  quadrigemina ;   2,  trian- 
gular band ;    3,  3,  superior  peduncles  of  the  cerebellum ; 
4,  4,  middle  peduncles  of  cerebellum ;  5,  5,  inferior  pedun- 
cles of  cerebellum  ;  6,  anterior  wall  of  fourth  ventricle ;  7, 
glosso-pharyngeal ;  8,  pneumogastric ;  9,  spinal  accessory ; 
from  10  to  10,  posterior  roots  of  eight  cervical  pairs :  the 
dorsal,  the  lumbar,  and  the  sacral  below  11  are  not  shown 
in  the  figure.     From  14  downward,  a  dotted  line  arising 
from  the  tearing  away  of  the  posterior  roots ;  15,  15,  an- 
terior roots  of  spinal  nerves,  the  dentated  ligament  being 
visible  through  the  removal  of  the  posterior  roots ;   16,  spi- 
nal ganglia,  of  which  there  are  thirty  pairs,  the  first  pair 
of  nerves  not  being  furnished  with  them  ;   17,  17,  anterior 
branches   of  spinal  nerves ;    18,  18,  posterior  branches; 
19,  19,  dentated  ligament,  placed  between  the  posterior 
and  anterior  roots ;  20,  same  ligament  brought  into  view. 

Fig.  143  shows  a  portion  of  the  spinal  cord  mgm  143- 
surrounded  by  its  envelopes,  and  seen  in  pro- 
file, so  as  to  display  at  once  the  origin  of  the 
anterior  and  posterior  roots.  1,1,  posterior 
roots  of  spinal  nerves  and  their  ganglia ;  2,  2,  anterior  roots 
of  the  same  nerves  anastomosing  with  the  anterior  portions 
of  these  ganglia;  3,  4,  anterior  and  posterior  roots  cut; 
5,  dentated  ligament ;  6,  dura  mater,  preserved  to  show  the 
sheaths  which  it  forms  around  these  ganglia  and  the  branches 
of  the  spinal  nerves ;  7,  vertical  section  of  the  sheath  of  the 
anterior  and  posterior  roots,  to  show  the  little  lamella  which 
separates  the  one  root  from  the  other;  8,  8,  interior  face. of 
the  dura  mater,  which  is  drawn  aside  to  show  the  smooth 
aspect  which  it  possesses,  owing  to  the  parietal  layer  of  the  rior  rootSt 
arachnoid  which  covers  it. 


J.gin  of  posterior 
roots  of  nerves. 


298  LONGITUDINAL   TRANSMISSION   IN   THE    CORD. 

The  white  or  fibrous  portion  of  the  spinal  cord  is  composed  in  part  of 
the  spinal  nerve  fibres  and  in  part  of  commissural  ones.  At  one  time  it 
was  supposed  that  every  one  of  the  preceding  continued  uninterruptedly 
to  the  brain.  On  this  point,  however,  the  weight  of  evidence  will  lead 
us  to  infer  that  the  vertical  distance  through  which  these  fibres  pass  is 
not  very  great,  and  that  they  are  soon  brought  in  connection  with  the 
interior  vesicular  substance.  If  all  the  fibres  passed  uninterruptedly  to 
the  brain,  we  should  expect  that  the  cord  would  increase  in  thickness  by  a 
regular  progression  upward ;  but  this,  as  is  shown  in  Fig.  138,  is  not  the 
case.  Its  enlargements  correspond  to  the  number  of  nerve  roots  given 
off  from  the  localities  in  which  they  occur.  Thus,  where  many  nerve 
roots  are  required  for  the  upper  extremities,  and  again  for  the  lower  ones, 
we  notice  such  corresponding  enlargements.  The  experiments  of  Volk- 
mann  show  that  these  dilatations  are  as  much  owing  to  an  increase  of 
the  vesicular  material  as  to  an  increased  number  of  fibres.  In  the  view 
presented  in  the  preceding  chapter  respecting  nerve-arcs  and  the  functions 
of  nerve-cells,  we  should  be  led  to  infer  that  every  centrifugal  and  cen- 
tripetal fibre  of  the  cord  is  brought  in  connection  with  such  a  cell  of  the 
gray  material,  and  that  it  does  not  extend  very  far  from  its  point  of  exit 
or  entrance. 

FUNCTIONS  OF  THE  SPINAL  CORD. — The  determination  of  the  func- 
Functions  of  tions  of  the  roots  of  the  spinal  nerves  by  Bell  has  already 
the  spinal  cord.  keen  referred  to  as  one  of  the  great  discoveries  of  physiol- 
ogy, and  as  furnishing  a  solid  foundation  for  an  exact  knowledge  of  the 
functions  of  the  nervous  system.  The  evidence  of  the  truth  of  the  doc- 
trine that  the  anterior  roots  of  these  nerves  are  motor  and  the  posterior 
Bell's  dis-  sensory,  is  complete.  Thus,  if  the  anterior  root  of  one  of  these 
covery.  nerves  be  divided,  all  those  parts  which  are  supplied  by  that 
nerve  will  exhibit  loss  of  motion,  though  their  sensation  is  unimpaired ; 
if  the  posterior  root  be  divided,  the  sensibility  of  the  parts  is  lost,  though 
the  power  of  motion  is  unaffected.  Similar  evidence  may  also  be  ob- 
tained by  irritating  the  ends  of  the  divided  roots,  muscular  motion  or 
pain,  as  the  case  may  be,  being  correspondingly  observed. 

The  spinal  cord  transmits  impressions  from  the  periphery  to  the  brain, 
Lon  itudinai  an<^  conversety  enables  the  brain  to  bring  into  action  the 
transmission  of  motor  nerves.  Division  of  it  at  once  causes  an  interruption 
ifluences.  Q£  voiuntaiy  motion  and  sensation  in  those  parts  supplied 
by  nerves  below  the  place  of  the  operation,  the  functions  of  the  parts 
above  remaining  unimpaired.  But,  though  the  influence  of  the  brain  in 
exciting  voluntary  motion,  and  its  capability  of  receiving  sensations,  is 
thus  cut  off,  the  severed  portion  of  the  cord  still  possesses  an  automatic 
power. 

This  transmission  of  influences  upward  or  downward  is  doubtless,  to 


TEANSVEESE   TEANSMISSION.  299 

a  considerable  degree,  accomplished  through  the  vesicular  substance,  the 
quality  of  which,  in  this  respect,  has  been  explained  in  the  preceding 
chapter.  But,  besides  this,  the  exterior  fibrous  structures  possess  a  like 
function,  correspondingly  as  they  are  connected  with  the  motor  or  sen- 
sory roots  of  the  nerves,  the  anterior  columns  being  motor,  and  the  pos- 
terior apparently  sensory. 

The  spinal  cord  not  only  permits  the  passage  of  influences  in  its  longi- 
tudinal, tut  also  in  its  transverse  direction.     This  is  what  Transverse 
might  be  anticipated  from  the  structure  and  functions  of  the  transmission  of 
cells  of  its  gray  interior.     If  the  cord  be  cut  half  through  in  u 
a  given  place,  and  again  be  cut  half  through  on  the  opposite  side,  at  a 
little  distance  above  or  below,  impressions  may  be  conducted  through 
the  intermediate  portion,  the  vesicular  material  being  then  their  only 
channel. 

In  a  memoir  on  the  distribution  of  the  fibres  of  the  sensitive  roots,  and 
on  the  transmission  of  impressions  in  the  spinal  cord,  Dr.  Brown.Se  uard 
Brown-Sequard,  referring  to  the  two  theories  entertained  at  on  the  conduc- 
present — 1st.  That  sensitive  impressions  reaching  the  cord  tlonofthecord- 
pass  in  totality  to  the  brain  along  the  posterior  columns ;  2d.  That  such 
impressions  so  arriving  pass  directly  to  the  central  gray  substance,  which 
transmits  them  upward — offers  reasons  for  supposing  that  both  these 
theories,  and  especially  the  first,  are  contradicted  by  facts. 

It  is  his  opinion  that  sensitive  impressions  reaching  the  cord  pass  in 
different  directions,  some  ascending,  others  descending,  but  both  going  in 
part  by  the  posterior  columns,  and  in  part  by  the  posterior  gray  horns, 
and  perhaps  by  the  lateral  columns,  to  penetrate,  after  a  short  distance, 
the  gray  central  substance  by  which,  or  in  which,  they  are  transmitted 
to  the  brain. 

He  also  shows  that  sensitive  impressions  of  one  lateral  half  of  the 
body  are  transmitted  principally  in  a  crossed  manner,  that  is  to  say,  that 
they  follow  more  particularly  the  opposite  half  of  the  cord  to  reach  the 
brain ;  that  the  decussation  of  the  conducting  elements  for  sensitive  im- 
pressions is  not  made,  as  is  commonly  said,  at  the  anterior  extremity  of 
the  pons ;  that  the  gray  substance  does  not  possess  the  property  of 
transmitting  sensitive  impressions  in  every  direction,  as  some  have  sup- 
posed ;  that  most,  if  not  all  the  conducting  elements  for  sensitive  im- 
•pressions  decussate  in  the  spinal  cord,  the  decussation  occurring  in  part 
almost  immediately  on  their  entry  into  the  cord,  but  that  a  few  make 
their  decussation  at  a  certain  distance  above  the  point  of  entry,  the  ma- 
jority, however,  descending  in  the  cord,  and  making  their  decussation 
below  the  point  of  entry ;  that  if  there  are  conducting  elements  for  sen- 
sitive impressions  which  ascend  throughout  the  entire  length  of  the  cord 
to  make  their  decussation  in  the  brain,  their  number  must  be  very  small ; 


300  REFLEX   ACTION. 

and  that  alterations  capable  of  producing  a  paralysis  of  sensibility,  and 
situated  upon  any  point  of  a  lateral  half  of  the  cerebro-spinal  axis,  al- 
ways produce  a  paralysis  of  sensibility  on  the  opposite  half  of  the  body, 
and  that  there  is  no  difference  between  the  brain  and  the  spinal  marrow 
in  this  respect. 

Thus  constructed,  the  spinal  cord,  as  we  shall  presently  show  from 
Analoo-  with  ^r*  Carpenter,  evidently  agrees  with  the  gangliated  ventral 
ventral  cord  cord  of  the  articulata,  each  portion  xof  it  from  which  a  pair  of 
lata'  nerves  is  given  off  representing  each  ganglion  of  that  ventral 
cord,  the  difference  in  the  two  structures  being,  that  in  the  spinal  col- 
umn the  ganglia  are  commissured,  so  as  to  form,  in  appearance,  one  con- 
tinuous mass,  and  agreeably  to  this  view  of  its  construction  are  the 
circumstances  under  which  its  enlargements  occur.  In  those  animal 
forms  in  which  the  entire  trunk  is  concerned  in  locomotion,  as  in  snakes 
and  eels,  the  cord  is  nearly  cylindrical;  but  as  soon  as  special  members 
for  locomotion  are  developed,  a  corresponding  increase  of  diameter  is  ob- 
served. Thus,  in  birds,  the  ganglionic  enlargement  corresponds  with  the 
region  from  which  the  nerves  for  the  wings  are  given  off;  but  in  that  tribe, 
as  in  the  ostrich,  the  mode  of  locomotion  of  which  is  by  the  legs  rather 
than  by  the  wings,  a  corresponding  posterior  enlargement  occurs.  The 
same  observations  may  even  be  more  distinctly  made  during  metamorph- 
oses ;  thus,  in  frogs,  while  they  are  in  the  tadpole  state  the  spinal  cord  is 
cylindrical,  but  bulging  ensues  in  it  anteriorly  and  posteriorly  as  soon  as 
the  anterior  and  posterior  members  are  developed. 

The  translation  of  impressions  which  have  been  brought  along  the 
Reflex  action  centripetal  fibres  into  motions,  the  exciting  influence  of  which 
of  the  cord.  {s  conveyed  along  the  centrifugal  fibres,  includes  what  is  un- 
derstood as  the  reflex  action  of  the  spinal  cord  as  developed  by  Dr.  Hall. 
Its  essential  condition  is  its  independence  of  the  agency  of  the  brain,  and 
therefore  unconscious  nature.  As  general  examples  may  be  mentioned 
the  movements  which  occur  in  swallowing ;  for  after  the  food  has  been 
carried  by  voluntary  action  into  the  fauces,  its  passage  onward  to  the 
stomach  is  perfectly  involuntary.  In  like  manner,  the  introduction  of  air 
into  the  lungs  in  ordinary  respiration  is  involuntary ;  for  though  it  may 
be,  to  a  certain  extent,  under  the  control  of  the  will,  yet  that  extent  is 
limited,  a  necessity  for  the  motion  presently  arising,  which  soon  becomes 
uncontrollable.  The  action  of  the  valvular  arrangements  at  the  cardiac 
and  pyloric  orifices  of  the  stomach,  and  the  constant  contraction  of  the 
sphincter  *ani,  are  farther  illustrations.  To  these  may  be  added  those 
impulsive  movements  which  we  instinctively  make  on  the  approach  of 
danger  or  in  the  act  of  falling,  and  perhaps,  too,  automatic  walking,  as 
we  go  from  place  to  place  in  a  state  of  mental  abstraction,  paying  no  at- 
tention to  the  course  we  take. 


REFLEX  ACTION. 


301 


The  cord  is  to  be  regarded  as  a  longitudinal  series  of  simple  automatic 
nerve  arcs,  or,  as  we  have  termed  it,  a  multiple  automatic  Automatic  ac- 
arc.  Each  segment  of  it  has  therefore  an  independent  action  tionofthecord. 
of  its  own,  but  can  conspire  with  its  neighbors  or  be  influenced  by  the 

brain,  by  means  of  its  commissural 
fibres,  an  arrangement  of  which  num- 
berless interesting  instances  might  be 
furnished.  The  one  represented  in 
Fig.  144,  which  is  from  the  cord  of 
spirostreptus,  may,  however,  suffice: 
A,  under  surface  of  a  portion ;  B,  up- 
per surface;  a,  inferior  longitudinal 
fibres ;  e,  superior  longitudinal  fibres ; 
y,  fibres  of  re-enforcement,  seen  also 
at  b  and  c\  g,  commissural  fibres,  seen 
also  at  d. 

The  power  which  the  cord  displays 
in  this  simple  action  is  most  striking- 
ly seen  when  it  is  cut  off  from  its 
cranial  connections.  The  decapitated 
frog  props  himself  up  stiffly  on  his 
legs,  and,  if  his  cutaneous  surface  be 
irritated,  exhibits  antagonizing  mo- 
tions ;  such  motions  are  all  of  the  reflex  character,  and  are  commonly 
much  more  strikingly  seen  in  cold  than  in  warm-blooded  animals ;  but 
even  in  man  precisely  the  same  results  are  witnessed  during  periods  of 
the  suspension  of  the  activity  of  the  brain,  as,  when  the  palm  of  the  hand 
of  a  sleeping  child  is  touched  with  the  finger,  the  finger  is  at  once  grasped. 
As  above  stated,  this  reflex  function  of  the  cord  is  therefore  independ- 
ent of  the  brain,  though  the  brain  can  control  it,  and  this  Reflex  action 
the  more  perfectly  the  higher  the  organization  of  the  animal,  independent  of 
Breathing  can  go  on,  whether  we  pay  attention  to  it  or  not,  * 
but  we  can  arrest  it  if  we  choose  for  a  time ;  and  since  in  man  this  in- 
troduction of  air  is  incidentally  used  for  very  refined  purposes,  by  volun- 
tary exertion  we  moderate  or  regulate  it,  as  in  the  production  of  musical 
sounds  in  singing  or  of  articulate  sounds  in  speech. 

In  a  general  way,  there  is  not  much  difficulty  in  distinguishing  be- 
tween simple  actions  of  the  cord  and  those  in  which  the  brain  Distinction  be- 
is  participating.     In  the  former,  no  weariness  or  fatigue  is  ^cerebral 
ever  experienced ;  in  the  latter  it  is ;  and  perhaps,  even  in  action, 
these  last,  involving  voluntary  muscular  action,  though  the  control  is  to 
be  attributed  to  the  brain,  the  source  of  the  force  is  in  the  cord. 

These  normal  phenomena  which  the  cord  displays  become  greatly  ex- 


Portion  of  cord  of  spirostreptus. 


302  [RELATIONS   OF   THE   SPINAL   CORD   AND   BRAIN.N 

Increase  of  aggerated  in  certain  conditions  of  disease,  as,  for  example,  in 
spinal  action,  tetanus,  in  which  the  slightest  peripheral  irritation  may  be 
followed  by  violent  convulsive  movement,  or  the  same  occurs  by  the 
agency  of  powerful  poisonous  substances,  as  strychnine.  In  these  cases 
the  action  may  be  either  limited  simply  to  the  cord,  as  in  the  tetanus 
brought  on  by  opium  in  frogs,  or  the  brain  may  be  involved  in  it,  as  in 
cases  of  hydrophobia,  in  which  the  sound  or  sight  of  water,  operating 
through  the  cerebrum,  will  produce  spasmodic  convulsions. 

From  the  facts  presented  by  the  lower  animals,  it  may  be  inferred  that 
the  spinal  cord  does  not  act  as  a  single  organ,  but  rather  should  be  re- 
garded as  a  collection  of  ganglia,  special  duties  being  discharged  by  spe- 
cial parts  of  it. 

With  respect  to  the  commissural  action  of  the  spinal  cord,  reference  has 
Connection  of  a^rea^7  ^een  made  to  the  structural  connection  between  the 
the  cord  and  cord  and  the  nervous  regions  above  it,  and  in  referring  to  the 
old  anatomical  doctrine  that  each  of  the  spinal  nerves  is  con- 
nected by  continuous  fibres  with  the  brain,  due  weight  has  been  given 
to  the  fact  that  the  cord  does  not  increase  in  thickness  as  it  approaches 
the  brain,  but  that  its  bulgings  correspond  to  the  regions  from  which  it  is 
necessary  that  an  unusual  supply  of  nerves  should  be  given  off.  The 
force  of  this  argument  is,  however,  considerably  diminished  when  we 
recollect  that  the  nerve-tubes  are  by  no  means  of  uniform  diameter,  but 
are  doubly  conical  in  shape.  Even,  therefore,  with  a  diminished  diame- 
ter of  the  spinal  cord,  there  might  be  an  upward  continuation  of  spinal 
fibres,  the  diameter  of  which  is  becoming  less  and  less ;  and  this  seems 
to  be  rendered  more  likely  from  the  analogy  of  the  structure  of  the  ven- 
tral cord  of  the  articulata,  in  which  fibres  are  sent  to  the  cephalic  gan- 
glia for  the  purpose  of  establishing  a  communication  between  them  and 
the  roots  of  the  nerves.  But,  however  that  may  be,  there  can  be  no 
question  of  the  influence  of  the  brain  over  spinal  action,  and  this,  of  course, 
implies  structural  connection  of  some  kind — an  intercommunication — 
which,  if  it  does  not  take  place  solely  through  the  white  columns,  must 
take  place  through  the  gray  material.  It  is,  however,  important  to  ob- 
serve that  the  gray  material  has  no  direct  communication  with  that  of 
the  cerebrum,  but,  passing  through  the  optic  thalamus,  ends  in  the  cor- 
pus striatum,  extending  therefore  in  one  continued  mass  through  the  cord, 
and  terminating  in  that  ganglionic  organ.  By  one  or  both  of  these  chan- 
nels, white  or  gray,  the  impressions  which  are  made  upon  the  spinal 
sensitive  nerves  are  presented  to  the  brain,  and  in  a  similar  manner  the 
influences  which  produce  voluntary  motions  are  transmitted  down.  A 
Effect  of  le  sect^on  °^  an7  Part  °^ tne  sPmal  cor<l  at  once  incapacitates  the 
sionsofthe  will  from  acting  upon  the  parts  beyond,  the  motions  of  which 
cord<  become  therefore  purely  automatic,  though  the  parts  above  still 


FUNCTIONS  OF  THE  SPINAL  CORD.  303 

display  their  customary  phenomena.  These  effects  are  sometimes  in- 
structively witnessed  in  man  when  lesions  of  the  cord  have  occurred 
through  disease. 

If  the  view  that  has  been  presented  respecting  the  continuation  of 
fibres  from  the  cord  to  the  brain  be  correct,  these  fibres  dis-  ,,  . 

1  Motor  and  sen- 

charge  a  commissural  duty.     This  would  lead  us  to  sup-  sory  tracts  of 

pose  that  there  is  a  correspondence  between  the  functions  of  { 
the  columns  of  the  cord  and  those  of  the  roots  of  the  spinal  nerves,  the 
anterior  columns  being  motiferous,  or  in  unison  with  the  motor  root  of 
the  nerves,  the  posterior  being  sensiferous,  or  in  unison  with  the  sensory 
root  of  the  nerves.  Agreeably  to  this,  if  the  anterior  columns  be  irri- 
tated, motions  are  excited  in  all  those  parts  which  are  supplied  with 
nerves  beyond  the  irritated  point ;  and  if  the  posterior  columns  be  irri- 
tated, in  like  manner  pain  is  experienced.  In  this  instance,  however,  a 
certain  amount  of  motion  is  occasionally  observed,  but  this  has  common- 
ly been  explained  by  referring  it  to  reflexion  within  the  cord.  It  has 
also  been  observed,  as  strengthening  these  views,  that  if  the  posterior 
columns  be  irritated  after  complete  section  of  the  cord,  the  result  will  de- 
pend on  which  of  the  cut  portions  be  disturbed ;  if  it  be  the  lower,  there 
will  be  no  effect.  An  examination,  under  the  same  circumstances,  of  the 
anterior  columns,  demonstrates  that,  if  the  upper  section  be  irritated,  there 
is  no  effect  produced ;  if  the  lower,  there  are  convulsive  movements  of 
the  parts  supplied  with  nerves  beyond. 

From  these  results  we  should  infer  that  the  physiological  functions  of 
the  anterior  and  posterior  roots  of  the  spinal  nerves  are  participated  in 
by  the  anterior  and  posterior  columns  of  the  cord,  and  might  therefore 
expect  that  those  functions  would  be  continued  in  the  higher  distribu- 
tion of  the  columns  above  the  medulla  oblongata. 

From  the  point  of  view  under  which  we  have  thus  presented  it,  the 
action  of  the  spinal  cord  is  therefore  simple,  or  it  is  disturb-  General  funo 
ed  by  the  agency  of  the  brain ;  in  the  first  case  it  offers  it-  tions  of  the 
self  purely  as  an  automatic  instrument ;  in  the  latter,  its  com- 
missural connections  with  the  brain  make  a  compound  apparatus.  The 
former  state  is  closely  represented  in  the  construction  of  the  amphioxus, 
the  nervous  system  of  which  has  no  rudiment  of  a  cerebrum  or  cerebel- 
lum ;  in  this  animal,  therefore,  since  also  the  sensory  ganglia  are  merely 
in  a  rudimentary  state,  the  mode  of  life  must  be  purely  mechanical,  just 
as  it  is  with  an  artificial  automaton,  of  which,  when  a  given  spring  is 
touched,  a  given  motion  is  made.  Even  among  the  highest  vertebrated 
animals,  man  himself  at  the  periodic  times  of  quiescence  of  the  cerebrum, 
as  in  sleep,  when  the  cerebral  influence  over  other  portions  is,  to  a  certain 
extent,  suspended,  an  approach  to  a  similar  condition  occurs ;  but  in 
periods  of  activity  of  the  cerebrum,  it  can  hold  the  spinal  cord  in  check, 


304  THE  MEDULLA  OBLONGATA. 

controlling,  and  in  some  cases  arresting  its  action,  and  this  is  done  through 
influences  propagated  along  the  tubular  structures  of  the  posterior  and  an- 
terior columns,  which  therefore  are  to  be  regarded,  in  this  respect,  as 
commissures  to  the  brain. 

OF  THE  MEDULLA  OBLONGATA. 

The  medulla  oblongata  is  a  conical  body,  lying  between  the  spinal  cord 
Limits  of  the  an<^  ^e  brain.  ^  *s  generally  understood  to  be  bounded  at 
medulla  obion-  its  upper  portion  by  the  pons  varolii,  but  this  is  not  a  true 
limit,  since  its  structure  extends  through  the  pons  varolii  to 
the  crura  of  the  brain.  There  is  the  same  indefiniteness  of  limit  as  re- 
spects its  lower  boundary,  which  is  generally  said  to  be  marked  by  some 
decussating  fibres  which  appear  on  its  front.  Like  the  spinal  cord,  it 
Its  subdivis-  has  an  anterior  and  posterior  fissure,  which  divide  it  into  two 
ions.  symmetrical  lateral  halves ;  the  former  is  a  continuation  of 

the  anterior  spinal  fissure,  the  latter  of  the  posterior,  and  ends  in  the  ca- 
lamus scriptorius  above.  The  lateral  halves  thus  produced  are  marked 
by  three  grooves,  producing  four  eminences,  which  pass  under  the  follow- 
ing names :  1st.  The  anterior  pyramids ;  2d.  The  olivary  bodies ;  3d. 
The  restiform  bodies ;  4th.  The  posterior  pyramids.  The  anterior  fis- 
sure is  crossed  about  an  inch  below  the  pons  varolii  by  decussating  fibres, 
and  hence  injuries  on  one  side  of  the  brain  produce  nervous  effects  on  the 
opposite  side  of  the  body. 

First.  The  anterior  pyramids  consist  of  white  fibres  originating  near 
The  anterior  tne  decussating  fasciculi.  They  have  a  compound  structure, 
pyramids.  for  each  contains  fibres  arising  from  the  inner  side  of  the  op- 
posite anterior  column  of  the  cord,  and  also  fibres  from  its  own  side : 
they  pass  through  the  pons  varolii  into  the  crus  cerebri.  From  these 
pyramids  curved  fibres  pass  round  the  olivary  body,  and  are  lost  in  the 
restiform.  They  are  called  arciform  fibres. 

Second.  The  corpora  olivaria  receive  their  name  from  their  olive  shape. 
The  olivary  They  are  separated  by  a  groove  from  the  preceding  in  front, 
bodies.  an(j  by  another  groove  from  the  restiform  bodies  behind.  Ex- 
ternally, they  are  formed  of  white  tubular  tissue,  which  incloses  a  vesic- 
ular mass,  the  olivary  ganglion,  which  connects  with  the  vesicular  struc- 
ture of  the  pons  above,  and  that  of  the  cord  below.  The  fibres  of  these 
ganglia  are  called  the  olivary  tracts.  They  are  continuous  with  the  cen- 
tral part  of  the  medulla  oblongata,  passing  behind  the  pyramids,  extend- 
ing upward  along  the  posterior  part  of  the  crura  cerebri  to  the  optic  thai- 
ami  and  tubercula  quadrigemina.  The  olivary  bodies  exist  only  in  man 
and  the  monkey  tribe. 

Third.  The  restiform  bodies  are  separated  from  the  olivary  by  a 
groove.  They  are  continuous  with  the  posterior  and  antero-lateral  col- 


THE  MEDULLA  OBLOXGATA. 


145. 


umns  of  the  cord.     Ascending,  they  enter  the  cerebellum,  and  The  restifbrm 
are  continuous  with  the  inner  part  of  its  cms.     They  there-  k°dies- 
fore  are  a  tract  of  communication  from  the  spinal  cord  to  the  cerebellum. 
They  each  inclose  a  gray  nucleus,  which  is  the  ganglion  of  the  pneumo- 
gastric  nerves,  and  of  some  of  the  roots  of  the  glosso-pharyngeal. 

Fourth.  The  posterior  pyramids  are  doubtfully  marked  off  from  the 
restiform  bodies  in  front,  and  are  separated  from  each  other  The  posterior 
by  the  posterior  fissure.      Superiorly,  their  fibres  are  contin-  pyramid*. 
uous  with  the  sensory  tract  of  the  crura  cerebri  :  their  gray  nuclei  are 
the  ganglia  of  the  auditory  nerves. 

The  structure  of  the  medulla  oblongata  is  exempli- 
fied in  the  annexed  figures. 

Fig.  145:  1,  chiasm  of  the  optic  nerves;  2,  crus  cere- 
bri ;  3,  tuber  cinereum  ;  4,  corpora  albicantia  ;  5,  locus 
.perforatus  ;  6,  pons  varolii  ;  7,  section  of  the  middle 
peduncle  of  cerebellum  ;  8,  transverse  fissure,  separa- 
ting the  medulla  from  the  pons  ;  9,  first  enlargement 
of  the  cord,  or  medulla  oblongata  ;  10,  anterior  pyra- 
mid; 11,  olivary  body;  12,  anterior  portion  of  resti- 
form body  ;  13,  neck  of  the  medulla  oblongata;  from 
16  downward  is  the  anterior  median  fissure;  from  17 
downward,  the  anterior  lateral  furrow. 

Fig.  146:  1,  section  of  optic 
tract;  2,  tubercula  quadrigemina  ; 
3,  triangular  band  ;  4,  section  of  crus  cerebelli  ;  5, 
medulla  oblongata  ;  6,  anterior  floor  of  the  fourth  ven- 
tricle ;  7,  median  fissure  of  the  fourth  ventricle,  aid- 
ing to  form  the  calamus  scriptorius  ;  8,  mammillary 
swelling  near  the  nib  of  the  pen  ;  9,  posterior  portion 
of  the  restiform  body;  from  12  down- 
ward, posterior  median  fissure  ;  from 
13  downward,  lateral  furrow  ;  from  14 
downward,  posterior  furrow. 

T-T.      *  i  «•       /•»  •  ^  t>  ,  i 

Juig.  147:  o,  anterior  column  ot  the 
cord,  divided  superiorly  into  two  portions,  of  which  the 
most  internal  one  contributes  to  the  formation  of  the  cor- 
responding pyramid;  7,  middle  or  lateral  column,  di- 
vided superiorly  into  three  or  four  portions,  decussating 
with  as  many  portions  of  the  column  of  the  opposite  side, 
the  decussation  taking  place  both  laterally  and  antero- 
posteriorly  :  it  is  the  origin  of  the  internal  two  thirds 
of  the  pyramid  ;  8,  8,  pyramids  ;  9,  white  fibres  of  the 
pyramid,  traversing  the  pons,  and  continuing  to  the  crus 
'U 


Fig.  140. 


Front  of  medulla  ob- 
longata. 


Fig.  147. 


Posterior  view  of  medulla 


306 


THE   MEDULLA    OBLONGATA. 


Fig.  148. 


Posterior  view  of  medulla  oblongata. 


cerebri ;  10,  superficial  section  of  the  trans- 
verse fibres  of  the  pons ;  11,  deeper  section 
of  the  transverse  fibres  of  the  pons  ;  12,  oli- 
vary body ;  13,  right  olivary  body,  brought 
into  view  by  removal  of  the  corresponding 
pyramid. 

Fig.  148  is  a  posterior  view  of  the  me- 
dulla oblongata :  p,  p,  posterior  pyramids, 
separated  by  a  posterior  fissure ;  r,  r,  resti- 
form  bodies,  composed  of,  <?,  c,  posterior  col- 
umns, and  </,  d,  part  of  antero-lateral  col- 
umns of  the  cord ;  <2,  #,  olivary  columns,  as 
seen  on  the  floor  of  the  fourth  ventricle,  sep- 
arated by  s,  the  median  fissure,  and  crossed 
by  some  fibres  of  origin  of,  n,  ft,  the  seventh 
pair  of  nerves. 


FUNCTIONS  OF  THE  MEDULLA  OBLONGATA. 

Viewed  as  a  superposed  continuation  of  the  spinal  cord,  the  medulla 
Functions  of  oblongata  is  the  tract  of  communication  between  that  organ 

the  medulla :     an(j  the  brain :  the  anterior  pyramids  and  olivary  tracts  con- 
it  is  a  tract  of  .    „  ,      ™        ....  J  , 
communica-      vey  motor  influences,  and  the  resmorm  tracts  and  posterior 

tion-  pyramids  sensations.  By  experiments  similar  to  those  which 

have  been  performed  upon  the  cord,  these  conclusions  have  been  main- 
tained. 

But,  besides  this  function  of  conduction,  the  medulla  oblongata  dis- 
charges a  most  important  duty  as  a  nervous  centre ;  on  it  depend  respi- 
ration and  deglutition.  The  brain  may  be  wholly  removed  above,  and 
the  spinal  cord  below,  as  far  as  the  origin  of  the  phrenic  nerve,  without 
death  necessarily  ensuing,  but  on  wounding  the  medulla  oblongata,  the 
muscular  movements  necessary  for  the  introduction  of  air  are  necessarily 
stopped. 

Moreover,  the  medulla  oblongata  exhibits  the  property  of  reflex  action. 
Its  relations  to  So  far  as  the  function  of  respiration  is  concerned,  its  chief 
respiration.  centripetal  nerve  is  the  pneumogastric,  but  the  power  which 
it  possesses  is  participated  in  by  many  others,  perhaps  by  reason  of  the 
venous  condition  into  which  the  blood  is  brought  from  want  of  proper 
aeration.  The  violent  respiratory  movements  by  the  sudden  application 
of  cold  to  the  skin,  the  shower-bath,  or  dashing  cold  water  on  the  face, 
are  converted  by  it  into  respiratory  muscular  motions.  From  it  also 
arise  the  movements  required  in  the  act  of  deglutition. 

Under  this  view  of  the  functions  of  the  medulla  oblongata,  it  is  to  be 
regarded  as  an  exclusively  automatic  instrument,  which  can  continue  its 


THE   PONS  VAEOLII.  307 

operation  after  the  excision  of  the  brain.  As  with  the  spinal  cord,  so 
with  it :  its  simple  action  may  continue  though  its  commissural  action 
has  ceased,  and  this  either  through  conditions  of  disease  or  by  the  ad- 
ministration of  drugs.  In  lesions  of  the  brain  respiration  may  still  con- 
tinue, as  it  may  also  when  sensation  and  voluntary  motion  have  been  ar- 
rested by  the  breathing  of  chloroform. 

OF  THE  PONS  VAKOLH. 

The  pons  varolii  consists  of  a  loop  of  fibres  passing  from  one  crus 
cerebelli  to  the  other,  around  the  tracts  of  communication  structure  of  the 
between  the  cord  and  the  brain.  As  shown  in  Fig.  145,  P°ns  varolii. 
they  do  not  form  a  continuous  superficial  commissure,  but,  at  a  certain 
distance  below,  interlace  with  the  fibres  of  the  pyramids ;  moreover, 
among  their  deeper  fibres  gray  vesicular  matter  occurs.  That  they  con- 
stitute mainly  a  commissure  for  the  cerebellum  is  apparent  from  the  cir- 
cumstance that,  in  those  animals  which  have  the  median  cerebellar  lobe 
only,  there  is  no  p'ons,  and  in  other  cases  its  relative  magnitude  is  in 
proportion  to  the  size  of  the  cerebellar  hemispheres. 

FUNCTIONS  OF  THE  PONS  VAKOLH. 

The  functions  of  the  pons  varolii  are  therefore  twofold:  it  acts  as  a 
conductor,  and  also  as  a  nerve  centre.  In  the  first  respect,  it  Functions  of 
is  the  channel  from  the  spinal  column  to  the  cerebrum  and  the  P°ns- 
cerebellum,  and  also  between  the  cerebellar  halves,  and  experiments  upon 
it,  in  giving  rise  to  sensations  and  motions,  are  in  conformity  with  what 
we  should  anticipate  from  the  structure  and  functions  of  the  spinal  cord. 

In  the  second  respect,  as  a  nervous  centre,  it  has  been  stated  that,  when 
the  cerebrum  and  cerebellum  are  removed,  but  the  pons  left  untouched, 
an  animal  gives  tokens  of  sensation  when  pinched  or  irritated,  and  like- 
wise executes  motions  which  have  an  object ;  these,  however,  were  no 
longer  observed  after  the  removal  of  the  pons. 

We  have  had  repeated  occasion  already  to  mention  that  the  surest 
guide  which  can  be  followed  in  interpretations  of  the  func- 

.  (.  ,  ,       .   T  ^        Dr.  Carpen- 

tions  of  the  nervous  system  is  comparative  physiology.     Our  ter's  views  of 
views  of  the  action  of  the  spinal  cord,  medulla  oblongata,  J^^H!" 
and  even  portions  above,  hereafter  to  be  described,  will  be  nai  cord  of  ver- 
rendered  clear  by  a  knowledge  of  the  structure  and  func-  j£e™entraid 
tions  of  the  ventral  cord  of  the  articulata,  the  analogy  of  cord  of  articu- 
which  to  the  parts  we  have  had  under  consideration  was    { 
first  correctly  pointed  out  by  Dr.  Carpenter.     I  therefore  transcribe  from 
his  General  and  Comparative  Physiology  the  following  paragraphs,  which 
present  his  views  with  perspicuity. 

"  The  plan  on  which  the  nervous  system  is  distributed  in  the  sub- 


308 


FUNCTIONS   OF   THE   CORD. 


Fig.  149. 


kingdom  articulata  exhibits  a  remarkable  uniformity  throughout  the 
whole  series,  while  its  character  gradually  becomes  more  elevated  as  we 
trace  it  from  the  lowest  to  the  highest  diyisions  of  the  group.  It  usu- 
ally consists  of  a  double  nervous  cord  studded  .with  ganglia  at  intervals, 
and  the  more  alike  the  different  segments,  the  more  equal  are  these  gan- 
glia. The  two  filaments  of  the  nervous  cord  are  sometimes 
at  a  considerable  distance  from  one  another,  and  the  ganglia 
are  distinct,  but  more  frequently  they  are  in  close  apposition, 
and  their  ganglia  appear  single  and  common  to  both.  That 
which  may  seem  as  the  typical  conformation  of  the  nervous 
system  of  this  group  is  seen  in  the  ganglionic  cord  of  scolo- 
pendra,  or  in  that  of  the  larvae  of  most  insects,  such  as  that 
of  the  sphinx  ligustri,  Fig.  149.  Here  we  see  the  nervous 
cord  nearly  uniform  throughout,  its  two  halves  being  sepa- 
rated, however,  in  the  anterior  portion  of  the  body.  The 
ganglia  are  disposed  at  tolerably  regular  intervals,  are  simi- 
lar to  each  other  in  size  (with  the  exception  of  the  last, 
which  is  formed  by  the  coalescence  of  two),  and  every  one 
supplies  its  own  segment,  and  has  little  connection  with  any 
other.  The  two  filaments  of  the  cord  diverge  behind  the 
head  to  inclose  the  oesophagus,  above  which  we  find  a  pair 
of  ganglia  that  receive  the  nerves  of  the  eyes  and  antennas. 
We  shall  find  that  in  the  higher  classes  the  inequality  in  the 
formation  and  office  of  the  different  segments,  and  the  in- 
creased powers,  of  special  sensation,  involve  a  considerable 
change  in  the  nervous  system,  which  is  concentrated  about 
the  head  and  thorax.  In  the  simplest  vermiform  tribes,  on 
the  other  hand,  we  lose  all  trace  of  separate  ganglia,  the  nervous  cord 
passing  without  evident  enlargement  from  one  extremity  to  the  other. 
Whatever  may  be  the  degree  of  multiplication  of  the  ganglia  of  the 
trunk,  they  seem  but  repetitions  of  one  another,  the  functions  of  each 
segment  being  the  same  with  those  of  the  rest.  The  cephalic  ganglia, 
however,  are  always  larger  and  more  important.  They  are  connected 
with  the  organs  of  special  sense,  and  they  evidently  possess  a  power  of 
directing  and  controlling  the  movements  of  the  entire  body,  while  the 
power  of  each  ganglion  of  the  trunk  is  confined  to  its  own  segment. 

"  The  longitudinal  ganglionic  cord  of  the  articulata  occupies  a  position 
which  seems  at  first  sight  altogether  different  from  that  of  the  nervous 
system  of  vertebrated  animals,  being  found  in  the  neighborhood  of  the 
ventral  or  inferior  surface  of  their  bodies,  instead  of  lying  just  beneath 
their  dorsal  or  upper  surface.  From  the  history  of  their  development, 
however,  and  from  some  other  considerations,  it  has  been  suggested  that 
the  whole  body  of  these  animals  may  be  considered  as  in  an  inverted  po- 


sphinx  Hgustri. 


FUNCTIONS   OF   THE    CORD.  309 

t 

sition,  the  part  in  which  the  segmentation  is  first  distinguished  in  insects 
being  the  equivalent  of  the  dorsal  region  in  vertebrata,  and  that  over 
which  the  germinal  membrane  is  last  to  close  in,  being  homologous  with 
the  ventral  region.  This  view  applies  also  to  the  position  of  the  dorsal 
vessel,  which  would  then  be  on  the  ventral  side  of  the  axis,  as  in  verte- 
brata. Eegarded  under  this  aspect,  the  longitudinal  nervous  tract  of  ar- 
ticulata  corresponds  with  the  spinal  cord  of  vertebrated  animals  in  posi- 
tion, as  we  shall  find  it  does  in  function. 

"  When  the  structure  of  the  chain  of  ganglia  is  more  particularly  in- 
quired into,  it  is  found  to  consist  of  two  distinct  tracts,  one  of  which  is 
composed  of  nerve  fibres  only,  and  passes  backward  from  the  cephalic 
ganglia  over  the  surface  of  all  the  ganglia  of  the  trunk,  giving  off 
branches  to  the  nerves  that  proceed  from  them,  while  the  other  includes 
the  ganglia  themselves.  Hence,  as  in  the  mollusca,  every  part  of  the 
body  has  two  sets  of  nervous  connections,  one  with  the  cephalic  ganglia, 
and  the  other  with  the  ganglion  of  its  own  segment.  Impressions  made 
upon  the  afferent  fibres  which  proceed  from  any  part  of  the  body  to  the 
cephalic  ganglia  become  sensations  when  conveyed  to  the  latter,  while  in 
respondence  to  these,  the  consensual  impulses,  operating  through  the  ce- 
phalic ganglia,  harmonize  and  direct  the  general  movements  of  the  body 
by  means  of  the  efferent  nerves  proceeding  from  them.  For  the  purely 
reflex  operations,  on  the  other  hand,  the  ganglia  of  the  ventral  cord  are 
sufficient,  each  one  ministering  to  the  actions  of  its  own  segment,  and  to 
a  certain  extent,  also,  to  those  of  other  segments.  It  has  been  ascertained 
by  t"he  careful  dissections  of  Mr.  Newport,  to  whom  we  owe  all  our  most 
accurate  knowledge  of  the  nervous  system  in  articulated  animals,  that  of 
the  fibres  constituting  the  roots  by  which  the  nerves  are  implanted  in 
the  ganglia,  some  pass  into  the  vesicular  matter  of  the  ganglion,  and,  after 
coming  into  relation  with  its  vesicular  substance,  pass  out  again  on  the 
same  side  (Fig.  150,  /*,  &),  while  a  second  set,  after  traversing  the  vesic- 
ular matter,  pass  out  by  the  trunks  proceeding  from  the  opposite  side  of 
the  same  ganglion,  and  a  third  set  run  along  the  portion  of  the  cord  which 

connects  the  ganglia  of  different  segments, 
and  enter  the  nervous  trunks  that  issue  from 
them  at  a  distance  of  one  or  more  ganglia 
above  or  below. 

"Fig.  150,  from  ganglionic  tract  of  poly- 
desmus  maculatus.  &,  interganglionic  cord  ; 
c,  anterior  nerves ;  d,  posterior ;  f,  Jc,  fibres 
of  reflex  action ;  </,  A,  commissural  fibres ;  i, 
longitudinal  fibres,  softened  and  enlarged  as 
they  pass  through  the  ganglionic  matter. 
»  Ganglion  of  poiydesmus  macuiatna.  "  Thus  it  appears  that  an  imrrassion  con- 


310  FUNCTIONS   OF   THE   CORD. 

veyed  by  an  afferent  fibre  to  any  ganglion  may  excite  motion  in  the  mus- 
cles of  the  same  side  of  its  own  segment,  or  in  those  of  the  opposite  side, 
or  in  those  of  segments  at  a  greater  or  less  distance,  according  to  the 
point  at  which  the  efferent  fibres  leave  the  cord ;  and  as  the  function  of 
these  ganglia  is  altogether  related  to  the  locomotive  actions  of  the  seg- 
ments, we  may  regard  them  as  so  many  repetitions  of  the  pedal  ganglia 
of  the  mollusca,  their  multiplication  being  in  precise  accordance  with  that 
of  the  instruments  which  they  supply. 

"  The  general  conformation  of  articulated  animals,  and  the  arrangement 
of  the  parts  of  their  nervous  systems,  render  them  peculiarly  favorable 
subjects  for  the  study  of  the  reflex  actions,  some  of  the  principal  phe- 
nomena of  which  will  now  be  described.  The  mantis  religiosa  custom- 
arily places  itself  in  a  curious  position,  especially  when  threatened  or  at- 
tacked, resting  on  its  two  posterior  pairs  of  legs,  and  elevating  its  thorax 
with  the  anterior  pair,  which  are  armed  with  powerful  claws ;  now  if  the 
anterior  segment  of  the  thorax,  with  its  attached  members,  be  removed, 
the  posterior  part  of  the  body  will  still  remain  balanced  upon  the  four 
legs  which  belong  to  it,  resisting  any  attempts  to  overthrow  it,  recover- 
ing its  position  when  disturbed,  and  performing  the  same  agitated  move- 
ments of  the  wings  and  elytra  as  when  the  unmutilated  insect  is  irritated ; 
on  the  other  hand,  the  detached  portion  of  the  thorax,  which  contains  a 
ganglion,  will,  when  separated  from  the  head,  set  in  motion  its  long  arms, 
and  impress  their  hooks  on  the  fingers  which  hold  it.  If  the  head  of  a 
centipede  be  cut  off  while  it  is  in  motion,  the  body  will  continue  to  move 
onward  by  the  action  of  the  legs,  and  the  same  will  take  place  in  the 
separate  parts  if  the  body  be  divided  into  several  distinct  portions. 
After  these  actions  have  come  to  an  end,  they  may  be  excited  again  by 
irritating  any  part  of  the  nervous  centres,  or  the  cut  extremity  of  the 
nervous  cord.  The  body  is  moved  forward  by  the  regular  and  successive 
action  of  the  legs,  as  in  the  natural  state,  but  its  movements  are  always 
forward,  never  backward,  and  are  only  directed  to  one  side  when  the  for- 
ward movement  is  checked  by  an  interposed  obstacle.  Hence,  though 
they  might  seem  to  indicate  consciousness  and  a  guiding  will,  they  do 
not  so  in  reality,  for  they  are  carried  on,  as  it  were,  mechanically,  and 
show  no  direction  of  object,  no  avoidance  of  danger.  If  the  body  be  op- 
posed in  its  progress  by  an  obstacle  of  not  more  than  half  of  its  own 
height,  it  mounts  over  it,  and  moves  directly  onward  as.  in  its  natural 
state  ;  but  if  the  obstacle  be  equal  to  its  own  height,  its  progress  is  arrest- 
ed, and  the  cut  extremity  of  the  body  remains  forced  up  against  the  op- 
posing substance,  the  legs  still  continuing  to  move.  If,  again,  the  nerv- 
ous cord  of  a  centipede  be  divided  in  the  middle  of  the  trunk,  so  that  the 
hinder  legs  are  cut  off  from  connection  with  the  cephalic  ganglia,  they 
will  continue  to  move,  but  not  in  harmony  with  those  of  the  fore  part  of* 


FUNCTIONS  OF  THE   CORD.  311 

the  body,  being  completely  paralyzed,  so  far  as  the  animal's  controlling 
power  is  concerned,  though  still  capable  of  performing  reflex  movements 
by  the  influence  of  their  own  ganglia,  which  may  thus  continue  to  propel 
the  body  in  opposition  to  the  determinations  of  the  animal  itself.  The 
case  is  still  more  remarkable  when  the  nervous  cord  is  not  merely  di- 
vided, but  a  portion  of  it  is  entirely  removed  from  the  middle  of  the  trunk ; 
for  the  anterior  legs  still  remain  obedient  to  the  animal's  control,  the  legs 
of  the  segments  from  which  the  nervous  cord  has  been  removed  are  alto- 
gether motionless,  while  those  of  the  posterior  segments  continue  to  act 
through  the  reflex  powers  of  their  own  ganglia,  in  a  manner  which  shows 
that  the  animal  has  no  power  of  checking  or  directing  them. 

"  The  stimulus  to  the  reflex  movements  of  the  legs  in  the  foregoing 
cases  appears  to  be  given  by  the  contact  of  the  extremities  with  the  solid 
surface  on  which  they  rest.  In  other  instances  the  appropriate  impression 
can  only  be  made  by  the  contact  of  liquid.  Thus  a  dytiscus  (a  kind  of 
water-beetle),  having  had  its  cephalic  ganglia  removed,  remained  motion- 
less as  long  as  it  rested  upon  a  dry  surface,  but  when  cast  into  water  it 
executed  the  usual  swimming  motions  with  great  energy  and  rapidity, 
striking  all  its  comrades  to  one  side  by  its  violence,  and  persisting  in 
these  for  more  than  half  an  hour.  Other  movements  again  may  be  ex- 
cited through  the  respiratory  surface.  Thus,  if  the  head  of  a  centipede 
be  cut  off,  and,  while  it  remains  at  rest,  some  irritating  vapor  (such  as 
that  of  ammonia  or  muriatic  acid)  be  caused  to  enter  the  air-tubes  on  one 
side  of  the  trunk,  the  body  will  be  immediately  bent  in  the  opposite  direc- 
tion, so  as  to  withdraw  itself  as  much  as  possible  from  the  influence  of 
the  vapor ;  if  the  same  irritation  be  then  applied  to  the  other  side,  the  re- 
verse movement  will  take  place,  and  the  body  may  be  caused  to  bend  in 
two  or  three  different  curves  by  bringing  the  irritating  vapor  into  the 
neighborhood  of  different  parts  of  either  side.  This  movement  is  evi- 
dently a  reflex  one,  and  serves  to  withdraw  the  entrances  of  the  air-tubes 
from  the  source  of  irritation,  in  the  same  manner  as  the  acts  of  coughing 
and  sneezing  in  the  higher  animals  cause  the  expulsion  from  the  air-pas- 
sages of  solid,  liquid,  or  gaseous  irritating  matters  which  may  have  found 
their  way  into  them. 

"From  these  and  similar  facts,  it  appears  that  the  ordinary  movements 
of  the  legs  and  wings  of  articulated  animals  are  of  a  reflex  nature,  and 
may  be  effected  solely  through  the  ganglia  with  which  these  organs  are 
severally  connected ;  while,  in  the  perfect  being,  they  are  harmonized, 
controlled,  and  directed  by  impulses  which  act  through  the  cephalic  gan- 
glia, and  the  nerves  proceeding  from  them.  There  is  strong  reaeon  to 
believe  that  the  operations  to  which  these  ganglia  are  subservient  are  al- 
most entirely  of  a  consensual  nature,  being  immediately  prompted  by 
sensations,  chiefly  those  of  sight,  and  seldom  or  never  by  any  processes 


312  FUNCTIONS    OF   THE    CORD. 

of  a  truly  rational  character.  When  we  attentively  consider  the  habits 
of  these  animals,  we  find  that  their  actions,  though  evidently  directed  to 
the  attainment  of  certain  ends,  are  very  far  from  being  of  the  same  spon- 
taneous nature,  or  from  possessing  the  same  designed  adaptation  of  means 
to  ends  as  those  performed  by  ourselves,  or  by  the  more  intelligent  ver- 
tebrata  under  like  circumstances.  We  judge  of  this  by  their  unvarying 
character,  the  different  individuals  of  the  same  species  executing  pre- 
cisely the  same  movements  when  the  circumstances  are  the  same,  and 
by  the  very  elaborate  nature  of  the  mental  emotions  which  would  be  re- 
quired in  many  instances  to  arrive  at  the  same  results  by  an  effort  of 
reason.  Of  such  we  can  not  have  a  more  remarkable  example  than  is 
to  be  found  in  the  operations  of  bees,  wasps,  and  other  social  insects, 
which  construct  habitations  for  themselves  upon  a  plan  which  the  most 
enlightened  human  intelligence,  working  according  to  the  most  refined 
geometrical  principles,  could  not  surpass,  but  which  yet  do  so  without 
education  communicated  by  their  parents  or  progressive  attempts  of  their 
own,  and  with  no  trace  of  hesitation,  confusion,  or  interruption,  the  dif- 
ferent individuals  of  the  community  all  laboring  effectively  to  one  pur- 
pose, because  their  automatic  impulses  (producing  what  are  usually  term- 
ed instinctive  actions)  are  all  of  the  same  nature. 

"  Not  only  are  the  locomotive  ganglia  multiplied  in  accordance  with  the 
repetition  of  segments  and  members,  but  the  respiratory  ganglia  are  mul- 
tiplied in  like  manner  in  accordance  with  a  repetition  of  respiratory  or- 
gans. The  respiratory  division  of  the  nervous  system  consists  of  a  chain 
of  minute  ganglia  lying  upon  the  larger  cord,  and  sending  off  its  delicate 
nerves  between  those  that  proceed  from  the  ganglia  of  the  latter,  as  seen 
in  Fig.  151.  These  respiratory  ganglia  and  their  nerves  are  best  seen  in 
the  thoracic  portion  of  the  cord,  where  the  cords  of  communication  be- 
tween the  pedal  ganglia  diverge  or  separate  from  one  another ;  and  this 
is  particularly  the  case  in  the  pupa  state,  when  the  whole  cord  is  being 
shortened  and  their  divergence  is  increased.  The  thoracic  portion  of  the 
cord  is  shown  in  Fig.  152,  B,  which  represents  the  second,  third,  and 
fourth  double  ganglia  of  the  ventral  cord,  the  cords  of  connection  between 
them  here  widely  diverging  laterally,  and  the  small  respiratory  ganglia 
which  are  connected  with  each  other  by  delicate  filaments  that  pass  over 
Fig.  151.  the  ganglia  of  the  ventral  cord,  and  which  send  off  lateral 
branches  that  are  distributed  to  the  air-tubes  and  other 
parts  of  the  respiratory  apparatus,  and  communicate  with 
those  of  the  other  system." 

Illustrations  of  the  nervous  system  of  the  articulata. 
Fig.  151,  A,  single  ganglion  of  centipede,  much  enlarged, 
showing  the  distinctness  of  the  purely  fibrous  tract,  b,  from 

Ganglion  of  centi-      ,-\  ••.       .  -,  -y-j.       .,  _,-»     -pj  .  /•    .1 

pede.  the  ganghonic   column,  a.     Fig.  152,  B,  portion  of  the 


THE   BRAIN. 


313 


Fig.  152.  'double  cord  from  the  thorax  of 

the  pupa  of  sphinx  ligustri, 
showing  the  respiratory  gan- 
glia and  nerves  between  the 
ganglia  2,  3,  4,  and  the  sepa- 
rated cords  of  the  locomotive 
system.  Fig.  153,  C,  view 
of  the  two  systems  combined, 
showing  their  arrangement  in 
the  larva :  «,  ganglion  of  the 
ventral  cord ;  £,  fibrous  tract 
passing  over  it ;  c,  <?,  respira- 
tory system  of  nerves,  distinct 
from  both. 

Having  thus  presented  the  views  of  Dr.  Carpen- 
ter respecting  the  analogy  between  the  ventral  cord 
of  the  articulata  and  the  spinal  cord  of  the  verte- 
brata,  I  should  next  continue  the  explanations 
which  this  pjiysiologist  has  offered  of  the  connec- 
tions and  relations  of  the  sensory  ganglia ;  but  this 
can  not  be  conveniently  done  until  we  have  passed 
through  the  description  of  the  organs  at  the  base  of 
the  brain. 


Thoracic  portion  of  cord  of 
sphinx  ligustri. 


CHAPTER  XVI. 

OF  THE  BRAIN. 

The  Brain:  its  Structure. — Its  Motor  and  Sensory  Parts,  Hemispheres,  and  Commissures. — 
The  Sensorium. —  Variations  of  the  Hemispheres  in  Size  and  Weight. — Instrumental  Nature 
of  Cerebrum. —  The  Cerebellum:  its  Structure  and  Functions. — Co-ordinates  muscular  Motions. 
—  Connection  with  Amativeness. — Phrenology. —  Conditions  of  Action  of  Brain. 

Symmetrical  Doubleness  of  the  Brain. — Function  of  each  Half,  and  of  both  conjointly. — Independ- 
ence and  Insubordination  of  each  Hemisphere. — Double  Thought. — Alternate  Thought. — Senti- 
ment of  Pre-existence. — Loss  of  Perception  of  Time. 

THE  cerebrum  and  cerebellum,  being  organs  additional  to  the  spinal 
cord,  and  developed,  as  has  been  shown  in  the  last  chapter,  n 

.  \      '  .  '    General  view 

upon  it,  the  cord  being  able  to  discharge  its  own  functions  of  structure  of 
independently  of  them,  we  shall  find  it  at  once  the  most  brain> 
natural  and  most  commodious  method  to  consider  their  structures  as 
arising  out  of  its  structure,  and  their  functions  as  having  relation  to  its 
functions. 

A  general  idea  of  the  structure  of  the  brain  as  an  appendage  to  the 


314  /         THE   BRAIN. 

spinal  cord  may  be  gathered  by  considering  that  »  a  bifurcation  of  the 
fibres  takes  place  in  the  medulla  oblongata,  and  upon  one  of  the  re- 
sulting bundles,  the  eras  cerebri,  the  cerebrum  is  formed,  on  the  other 
the  cerebellum.  The  crus  cerebri  is  composed  of  three  strands  :  an  infe- 
rior, the  fibres  of  which  have  come  from  the  anterior  pyramids,  and  in 
part  from  the  olivary  bodies.  This  strand  ends  in  the  corpus  striatum, 
its  fibres  not,  however,  blending  abruptly  with  the  vesicular  matter,  but 
passing  into  it  in  bundles.  It  is  essentially  motor.  A  superior,  which 
is  derived  from  the  posterior  pyramids,  and  terminates  in  the  thalamus. 
It  is  essentially  sensory.  Between  these,  constituting  the  third  portion  — 
strand  it  can  scarcely  with  propriety  be  called  —  is  a  layer  of  dark  vesic- 
ular material,  the  locus  niger.  It  is  to  be  understood  that  the  motor 
strands  of  the  opposite  sides  decussate  in  the  medulla  oblongata  ;  the 
sensory  strands  decussate  in  the  mesocephalon. 

The  other  bundle,  arising  in  the  original  bifurcation,  assumes  the  des- 
Formation  of  ignation  of  crus  cerebelli.  On  it  the  cerebellum  is  devel- 
the  cerebellum.  OpQ^t  It  consists  essentially  of  fibres  from  the  restiform 
bodies,  re-enforced  by  others  which  have  come  from  the  anterior  pyramids 
under  the  name  of  arciform  fibres.  These  together  make  their  way  to 
the  interior  ganglion  of  the  cerebellum,  the  corpus  dentatum,  and  there 
they  end.  But  the  crus  cerebelli  contains  likewise  two  other  great 
strands  :  an  inferior,  which  constitutes  the  commissure  of  the  two  cere- 
bellar  hemispheres,  and  which,  running  round  the  entire  prolongations  of 
the  spinal  cord,  forms  the  pons  varolii  ;  a  superior,  the  processus  cere- 
belli ad  testes,  which  unites  the  cerebellum  and  cerebrum. 

Of  the  portions  of  the  spinal  cord  on  which  the  cerebrum  is  to  be  de- 
veloped, those  which  are  sensory  end  in  the  optic  thalamus,  those  which 
are  motor  in  the  corpus  striatum.  The  thalamus  and  striatum  of  each 
side  may  be  regarded  as  one  compound  ganglion,  since,  like  the  columns 
of  the  cord,  they  are  united  by  a  gray  and  a  white  commissure.  Of  the 
portions  on  which  the  cerebellum  is  to  be  developed,  the  termination  is 
in  the  central  ganglion  of  the  cerebellum,  the  corpus  dentatum. 

At  the  place  of  bifurcation  of  the  constituent  strands  of  the  crus  cere- 
bri and  crus  cerebelli  from  each  other  in  the  medulla  oblon- 


"ar}  °  y'  gata,  there  is  intercalated  or  included  a  ganglion,  which,  with 
its  apparatus,  constitutes  the  olivary  body,  the  fibres  of  which  make 
their  way  upward  between  the  two  preceding  bundles,  and,  having  bi- 
furcated, one  branch  goes  to  the  quadrigemina  and  the  other  to  the  op- 
tic thalamus,  the  latter  constituting,  as  has  been  said,  a  part  of  the 
crus  cerebri.  The  seat  of  power  of  the  medulla  oblongata  is  in  this 
ganglion. 

Such  being  the  anatomical  construction  of  the  crus  cerebri,  it  may  be 
physiologically  regarded  as  a  compound-  strand,  the  anterior  portion  of 


THE   BRAIN.  315 

which  is  motor,  the  posterior  sensory ;  and  between  these  a  Nerves  of  the 
dark  vesicular  deposit,  the  locus  niger,  which  is  continuous  ^^^ifdsre^ 
between  the  vesicular  matter  in  the  spinal  cord  and  that  of  spectiveiy. 
the  thalamus  and  corpus  striatum.  From  the  lowest  extremity  of  the 
cord  to  these  great  ganglia  there  is,  therefore,  an  unbroken  vesicular 
channel.  In  its  progress  onward  to  the  corpus  striatum,  the  anterior 
strand  yields  roots  of  the  spinal  accessory,  hypoglossal,  facial,  abducens, 
the  small  root  of  the  fifth,  the  trochlearis,  and  the  oculo-motor  nerves. 
If  there  were  no  other  proof  of  the  motor  character  of  this  strand,  the 
motor  property  of  all  these  nerves  would  be  sufficient  to  determine  it. 
In  like  manner,  the  posterior  strand  yields  the  pneumogastric,  the  glosso- 
pharyngeal,  and  the  sensory  root  of  the  fifth,  from  the  sensory  functions 
of  which  its  sensory  character  is  established. 

The  layer  of  vesicular  matter  which  is  found  upon  the  cerebral  convo- 
lutions, and  which  is  doubtless  the  seat  of  the  higher  intel-  Relation  of  the 
lectual  qualities,  has  therefore  no  communication  with  the  ^roftoe hem- 
vesicular  matter  of  the  spinal  axis,  by  contact  or  continua-  ispheres. 
tion,  but  only  through  the  intervention  of  fibres  which  radiate  upon  it  in 
all  directions  from  the  thalamus  and  striatum,  or  rather  through  some 
which  radiate  from  the  great  sensory  centre,  the  thalamus,  to  the  periph- 
ery of  the  cerebrum,  and  others  which  converge  from  that  periphery  to 
the  great  motor  centre,  the  striatum.  If  the  diameter  of  these  fibres  be 
assumed  to  be  10ooo  of  an  inch,  there  must  be  many  millions  of  them 
in  the  aggregate.  The  vesicular  matter  of  the  hemisphere  is  arranged 
on  the  superficies  instead  of  centrally,  on  account  of  the  necessities  of 
their  structure  and  condition  of  activity,  for  thereby  a  great  surface  is 
obtained,  which  is  further  increased  by  the  artifice  of  convolutions,  a  ve- 
sicular surface  which,  counting  in  that  of  the  cerebellum,  has  been  esti- 
mated at  670  square  inches,  and  blood  can  be  copiously  supplied  and 
freely  removed. 

But  the  thalamus  and  striatum  are  only  two  of  a  chain  of  ganglia  be- 
neath the  cerebral  hemispheres.  Anteriorly  we  find  the  ol-  Gapglia  at  the 
factive  ganglia,  or  bulbs  of  the  olfactory  nerves,  which  are  base  of  the 
seated  upon  peduncles,  though  their  character  is  manifest  from 
the  gray  matter  they  contain.  Behind  these  are  the  tubercula  quadri- 
gemina,  to  which  the  optic  nerves  run,  and  which  are  therefore  their  gan- 
glionic  centres.  What  answers  to  the  auditory  ganglion  is  lodged  at  a 
distance  back,  at  the  fourth  ventricle,  and  the  gustatory  ganglion  is  in 
the  medulla  oblongata.  These  are  the  ganglia  of  special  sense,  and  to 
be  regarded  as  subordinate  to  the  thalamus, 'which  is  their  common 
register. 

All  these  parts  are  commissured  with  one  another,  and  with  their  fel- 
lows of  the  opposite  half  of  the  brain.     Indeed,  so  likewise  are  all  its 


316 


THE   BRAIN. 


Commissures  of  parts,  the  different  cerebral  lobes,  the  opposite  hemispheres, 
the  brain.  adjacent  and  distant  convolutions,  the  cerebrum  with  the 
cerebellum.  Hence  arises  a  structure  of  extreme  complexity.  Among 
the  commissural  apparatus  may  be  more  particularly  mentioned  the  cor- 
pus callosum,  the  fornix,  the  anterior,  the  posterior,  the  soft,  and  the  su- 
perior longitudinal  commissures. 

For  the  sake  of  a  clear  conception  of  the  structure  of  the  brain,  so  far 
Aspects  of  the  as  is  required  for  physiological  purposes,  the  annexed  repre- 
brain.  sentations  of  its  superficial  aspects  are  given.  These  are  a 

preparation  for  the  diagrammatic  sketches  which  follow,  and  which  ena- 
ble us  to  understand  the  relation  and  dependence  of  the  more  prominent 
parts.  It  need  scarcely  be  added  that  the  uses  and  functions  of  nearly 
all  the  subordinate  parts  are  at  present  wholly  unknown.  For  the  time 
being,  they  are  therefore  objects  of  interest  to  the  anatomist  rather  than 
to  the  physiologist. 

Fig.  154,  external  lateral  face  of  the  right  half  of  the  brain  :  1,  me- 
dulla oblongata;  2,  pons  varolii;  3,  cerebellum;  4,  pneumogastric  lob- 
ule ;  5,  frontal  convolutions  ;  6,  parietal  convolutions  ;  7,  occipital  con- 
volutions ;  8,  fissure  of  Sylvius  ;  9,  9,  its  two  branches. 


Fig.  154. 


Fig.  155. 


Superior  aspect  of  the  brain. 


External  lateral  face  of  the  brain. 

Fig.  155,  superior  aspect  of  the  brain: 
1, 1,  anterior  lobes ;  2, 2,  posterior  lobes ; 
3, 3,  great  median  fissure ;  4,  4,  fissures 
of  Eolando  ;  5,  5,  anterior  parietal  convolutions ;  6,  6,  posterior  parietal 
convolutions  ;  7,  7,  rudimentary  parietal  convolutions ;  8,  8,  frontal  con- 
volutions ;  9,  9,  occipital  convolutions. 

Fig.  156,  internal  lateral  face  of  the  right  half  of  the  brain :  1,  half 
of  medulla  oblongata ;  2,  half  of  pons  varolii ;  3,  half  of  eras  cerebri ;  4, 
arbor  vita?  of  cerebellum ;  5,  aqueduct  of  Sylvius  ;  6,  half  of  the  valve 
of  Vieussens  ;  7,  two  of  the  tubercula  quadrigemina;  8,  half  of  the  pin- 
eal gland ;  9,  its  inferior  peduncle ;  10,  its  anterior  peduncle ;  11,  trans- 
verse portion  of  the  fissure  of  Bichat :  12,  superior  face  of  the  optic  tract ; 


THE   BRAIN. 


317 


Internal  lateral  face  of  the  brain. 


13,  its  internal  face;  14,  commis- 
suramollis;  15,  infundibulum;  16, 
portion  of  pituitary  gland  ;  17,  por- 
tion of  tuber  cinereum ;  18,  pisiform 
tubercle;  19,  locus  perforatus;  20, 
oculo-inotor  nerve ;  21,  portion  of 
optic  nerve ;  22,  anterior  cerebral 
commissure ;  23,  foramen  of  Mon- 
roe ;  24,  fornix ;  25,  septum  luci- 
dum ;  26,  corpus  callosum ;  27, 
splenium  ;  28,  genu ;  29,  sinus  of 
the  corpus  callosum ;  30,  gyrus 
fornicatus ;  31,  internal  convolu- 
tion of  the  anterior  lobe  ;  32,  deep  anfractuosity ;  33,  convolution  of  pos- 
terior lobe ;  34,  anfractuosity. 

Fig.  157,  base  of  the  brain,  photo- 
graphed from  a  wax  cast :  1,  1,  anteri- 
or lobes  ;  2, 2,  middle  lobes  ;  3, 3,  pos- 
terior lobes;  4,  anterior  portion  of  great 
median  fissure;  5, its  posterior  portion; 
6,  6,  fissures  of  Sylvius  ;  7,  7,  antero- 
posterior  portions  of  the  great  fissure 
of  Bichat ;  8,  tuber  cinereum ;  9,  9, 
corpora  albicantia;  10,  locus  perforatus 
medius  ;  11, 11,  crura  cerebri;  12,  pons 
varolii;  13,  medulla  oblongata;  14, 
14,  anterior  pyramids;  15,  15,  olivary 
bodies;  16,  16,  restiform  bodies;  17, 
17,  lateral  lobes  of  the  cerebellum  ;  18, 
Base  of  the  brain.  portion  of  its  middle  lobe  ;  19,  19, 

two  small  antero-posterior  convolutions  of  the  frontal  lobe,  separated  by 
the  groove  of  the  olfactory  nerve ;  20,  oblique  convolution,  limiting  the 
fissure  of  Sylvius ;  21,  convolution  of  the  great  cerebral  fissure ;  22,  ol- 
factory nerve  ;  23,  its  bulb ;  24,  24,  optic  nerves  and  their  chiasm  ;  25, 
25,  oculo-motor  nerves  ;  26,  26,  pathetici ;  27,  27,  great  and  small  roots 
of  the  trifacial;  28, 28,  external  oculo-motor  nerves;  29, 29,  facial  nerves  ; 
30,  30,  auditory;  31,  31,  glosso-pharyngeal ;  32,  32,  pneumogastric 
nerves ;  33,  33,  spinal  accessory ;  34,  34,  great  hypoglossal.  In  this 
engraving  several  of  the  symmetrical  numbers  are  not  repeated,  for  the 
sake  of  clearness. 

Fig.  158  is  an  analytical  diagram  of  the  brain  in  a  vertical  section 
(from  Mayo).  It  serves  to  impress  on  the  mind  the  foregoing  structure  of 
structural  descriptions,  s,  Spinal  cord  preparing  for  bifurca-  t?e  brain- 


318 


STRUCTURE   OF   THE   BEAIN. 

Fig.  158. 


Diagram  of  the  structure  of  the  brain. 

tion  ;  r,  restiform  bodies  passing  to  <?,  the  cerebellum ;  d,  corpus  denta- 
tum  of  the  cerebellum  ;  0,  intercalation  of  the  olivary  body ;  f,  columns 
continuous  with  the  olivary  bodies  and  central  part  of  the  medulla  ob- 
longata,  and  ascending  to  the  tubercula  quadrigemina  and  optic  thalami ; 
JP,  anterior  pyramids  :  v,  pons  varolii ;  n,  b,  tubercula  quadrigemina ; 
<7,  geniculate  body  of  the  optic  thalamus ;  £,  processus  cerebelli  ad  testes; 
#,  anterior  lobe  of  the  brain ;  q,  posterior  lobe  of  the  brain. 

Fig.  159,  the  motor  tract  (from  Sir  C.  Bell).  A,  A,  fibres  of  the  hem- 
ispheres converging  to  form  the  anterior  portion  of  the  crus  cerebri ;  B, 
the  same  tract  when  passing  the  crus  cerebri ;  C,  the  right  pyramidal 
body,  a  little  above  the  point  of  decussation ;  D,  the  remaining  part  of 
the  pons  varolii,  a  portion  having  been  dissected  off  to  expose  B.  1, 
olfactory  nerve  in  outline ;  2,  union  of  optic  nerves  ;  3,  3,  motor  oculi ; 
4,  4,  patheticus  ;  5,  5,  trigeminus ;  6,  6,  its  muscular  division ;  7,  7,  its 
sensory  root ;  8,  origin  of  sensory  root  from  the  posterior  part  of  the  me- 
dulla oblongata ;  9,  abducens  oculi ;  10,  auditory  nerve;  11,  facial  nerve; 


THE   MOTOR  TRACT. 
Fig.  159. 


319 


The  motor  tract. 


12,  eighth  pair ;  13,  hypoglossal ;  14,  spinal  nerves  ;  15,  spinal  acces- 
sory of  right  side,  separated  from  par  vagum  and  glosso-pharyngeal. 

Fig.  160  (on  the  following  page),  the  sensory  tract  (from  Sir  C.  Bell). 
A,  pons  varolii ;  B,  B,  sensory  tract  separated ;  C,  union  of  posterior 
columns ;  D,  D,  posterior  roots  of  spinal  nerves ;  E,  sensory  roots  of  the 
fifth  pair. 

The  ganglia  at  the  base  of  the  brain  are  regarded  by  Dr.  Carpenter  as 
constituting  the  true  sensorium.  a  doctrine  which  he  has  es-  „. 

i  i  •  t  Thesensonum. 

tablished  by  many  weighty  arguments,  and  which  is  doubt- 
less one  of  the  most  important  thus  far  introduced  by  any  physiologist. 

The  idea  here  intended  to  be  conveyed  is,  that  the  thalami,  striata, 
sensory  ganglia,  and  nervous  arrangements  below,  constitute  an  isolated 
apparatus ;  distinct  from  which,  and  superadded,  are  the  cerebral  hem- 
ispheres. 

From  observations  on  the  animal  series,  the  conclusion  seems  to  be  un- 


320  THE   SENSORY  TRACT. 

Fig.  160. 


D 

The  sensory  tract. 

avoidable  that  the  chain  of  ganglia  now  under  consideration  must  con- 
stitute a  sensorium,  the  centripetal  fibres  communicating  their  impression 
and  motion  ensuing,  the  impressions  being  attended  with  consciousness. 
This  view  is  moreover  substantiated  by  observations  made  after  excision 
of  the  cerebrum,  a  certain  degree  of  consciousness  remaining,  not  unlike 
that  exhibited  by  a  man  who  is  half  asleep.  This  condition  of  things  is 
naturally  presented  in  the  amphioxus. 

But  after  the  cerebral  hemispheres  are  added,  an  impression  received 
Effect  of  the  ad  uP(:)n  ^ne  thalamus,  whether  it  has  come  in  through  the  sen- 
dition  of  the  sory  ganglia,  or  any  other  sensory  part  of  the  cranio-spinal 
axis,  is  transmitted  to  the  convolutions  along  the  radiating 
fibres.  From  the  convolutions,  the  influence  which  is  to  produce  mo- 
tion descends  along  the  converging  fibres  to  the  striatum,  thence  along 
the  inferior  layers  of  the  crus,  through  the  mesocephalon  to  the  anterior 
pyramids,  and  by  their  decussation  to  the  opposite  side  of  the  cord. 

Such  is  the  view  which  Dr.  Carpenter  presents  of  the  functions  of  the 
sensory  ganglia  and  spinal  axis ;  or,  employing  the  terms  we  have  pre- 
viously defined,  the  cord  alone  is  a  longitudinal  series  of  automatic  arcs  ; 
on  the  addition  of  the  thalamus  and  striatum,  it  becomes  a  compound 
registering  arc,  the  cerebral  hemispheres  finally  annexed  to  it  constitut- 
ing an  influential  arc. 

In  a  simple  arc,  an  impression  is  at  once  converted  into  motion,  and 
leaves  behind  it  no  traces ;  its  expenditure  is  instantaneous  and  complete. 
In  a  registering  arc,  a  part  of  the  impression  is  stored  up  or  remains — 


THE  CEREBRUM.  321 

nay,  even  the  whole  of  it  may  be  so  received  and  retained.  It  is  not  to 
be  overlooked  that,  as  soon  as  this  effect  occurs,  the  evidences  of  sensation 
arise ;  and,  since  sensation  necessarily  implies  the  existence  of  ideas, 
ideas  themselves  are  doubtless  dependent  on  this  partial  retention  or  reg- 
istry of  impressions.  We  may  therefore  adopt  the  doctrine  of  Dr.  Car- 
penter, as  regards  the  sensorial  functions  of  the  cranio-spinal  apparatus, 
not  only  from  the  arguments  he  has  presented,  but  also  from  other  con- 
siderations. 

There  can  be  no  doubt  that  the  cerebral  hemispheres  constitute  the  in- 
strument through  which  the  mind  exerts  its  influences  on  the  General  result 
body.  Any  injury  of  sufficient  severity  inflicted  upon  them  of  variations 

j.  ^        J     J         -Al_  x    1    1  f  •     x    11  in  the  Size  and 

is  at  once  attended  with  a  total  loss  of  intellectual  power;  weight  of  the 
any  malformation  or  lesion  by  disease  is  attended  by  a  dete-  hemisPheres- 
rioration  below  the  customary  mental  standard;  any  unusual  develop- 
ment with  correspondingly  increased  powers  of  intellection ;  and  this  not 
only  as  regards  animals  of  different  tribes,  or  individuals  at  special  peri- 
ods of  their  lives,  but  also  of  different  men  when  compared  with  one  an- 
other.    The  general  impression  is  founded  in  fact  that  those  who  have 
distinguished  themselves  for  mental  attainments  or  intellectual  power 
have  been  marked  by  the  unusual  development  of  their  cerebral  hemi- 
spheres. 

It  is  to  be  understood  that,  in  thus  asserting  a  correspondence  between 
the  development  of  the  cerebrum  and  intellectual  capability,  instrumental 
we  are  not  to  overlook  the  instrumental  nature  of  that  organ,  nature  of  cere- 
Though  imperfections  in  it  may  produce  a  manifest  inferior-  brum' 
Ity,  that  inferiority  is  by  no  means  to  be  referred  to  the  intellectual  prin- 
ciple itself.     The  mode  of  action  being  by  an  instrument,  if  that  instru- 
ment becomes  imperfect  the  action  becomes  imperfect  too.     Under  such 
circumstances,  in  any  human  contrivance,  we  should  never  think  of  im- 
puting inferiority  to  the  prime  mover. 

From  this  point  of  view  we  may  therefore  consider  the  intellectual  prin- 
ciple as  possessing  powers,  properties,  and  faculties  of  its  own  ;  as  being 
acted  on  by  impressions  existing  in  the  thalamus,  and  delivered  through 
the  intervening  fibrous  structures  to  the  vesicular  material  of  the  convolu- 
tions of  the  cerebral  hemispheres.  In  this  region  they  act  upon  the  in- 
tellectual principle  and  are  acted  upon  by  it,  the  returning  influence,  if 
any,  coming  down  through  the  converging  tubular  structures  to  the  cor- 
pus striatum,  and  by  its  commissural  connections  sent  off  to  particular 
ganglia,  passing  along  the  inferior  strand  of  the  crus  through  the  meso- 
cephalon  to  the  anterior  pyramids,  and  by  their  decussation  to  the  oppo- 
site side  of  the  cord. 

Having  thus  spoken  of  the  sensory  ganglia  and  the  cerebral  hemi- 
spheres, it  remains  to  add  some  remarks  respecting  the  cerebellum.  It 

X 


322  STRUCTURE    OF   THE    CEREBELLUM. 

The  cerebel-  arises,  as  has  been  stated,  from  the  triple  strand  of  the  eras 
lum.  cerebelli,  of  which  one  layer  of  fibres  is  connected  with  the 

corpora  quadrigemina,  and  through  them  with  the  optic  thalami ;  a  sec- 
ond with  the  restiform  bodies ;  and  the  third  is  commissural,  and  passes 
forward  as  the  pons  varolii. 

Like  the  cerebrum,  this  organ  is  vesicular  on  its  surface,  which  pre- 
sents a  number  of  parallel  lines,  which  are  fissures  descending  to  the  in- 
terior. Their  object  is  apparently  the  same  as  that  of  the  convolutions 
of  the  brain,  the  augmentation  of  surface.  Of  these  fissures,  the  deep 
are  termed  the  primary :  they  divide  the  organ  into  lobes.  Those  which 
descend  to  a  less  depth  are  termed  secondary :  the  divisions  they  give 
rise  to  are  lobules.  The  gray  vesicular  material  does  not,  however,  de- 
scend to  the  bottom  of  the  primary  fissures,  and  in  this  respect  they  dif- 
fer from  the  cerebral  convolutions.  Moreover,  from  this  circumstance, 
that  material  is  not  continuous  all  over  the  cerebellum,  but  is  in  divided 
portions. 

Such  are  the  appearances  presented  on  an  exterior  examination  of 
Structure  of  ^ie  cerebellum.  Viewed  as  a  development  upon  the  crura 
the  cerebellum,  cerebelli,  it  may  be  described  as  consisting  of  a  median  lobe 
and  two  hemispheres ;  the  former  is,  however,  found  existing  alone  in  fish- 
es and  reptiles,  the  latter  being  subsequently  added  in  the  higher  tribes. 
From  the  central  column  of  each  hemisphere  white  fibrous  planes  are 
given  off,  and  from  these,  again,  secondary,  and  again,  tertiary  planes 
proceed.  The  planes  are  covered  with  vesicular  matter,  and  thus  give 
rise  to  the  appearance  spoken  of  in  the  preceding  paragraph,  in  the  exte- 
rior examination  of  the  cerebellum,  as  primary  and  secondary  fissures.' 
They  are  lined  with  pia  mater.  The  median  lobe  is  formed  on  the  same 
plan.  Its  fibrous  stem  comes  from  the  processus  cerebelli  ad  testes,  or, 
more  properly,  from  the  optic  thalamus.  The  weight  of  the  cerebellum, 
compared  with  that  of  the  cerebrum,  is  usually  stated  as  being  about  1  to  8. 

Much  diversity  of  opinion  prevails  respecting  the  true  function  of  the 
cerebellum,  some  supposing  that  it  is  the  centre  of  common  sensation, 
others  that  it  is  for  the  purpose  of  co-ordinating  muscular  movement, 
and  others  that  it  is  the  seat  of  sexual  instinct. 

That  the  cerebellum  is  one  of  the  sensory  ganglia  may  be  inferred  from 
Function  of  the  the  history  of  its  development  and  its  anatomical  connec- 
cerebeiium.  tions.  Its  median  lobe  is  the  first  to  appear,  as  in  fishes, 
and  the  hemispheres  arise  subsequently  as  appendages  thereto,  as  in 
birds.  The  size  which  these  eventually  attain  gives  them  a  deceptive 
prominence,  and  hides  their  subordinate  character.  Regarding  the  lobe, 
therefore,  as  the  essential  and  fundamental  portion  of  the  structure,  the 
significance  of  its  cerebral  connection  with  the  thalamus  through  the  pro- 
cessus ad  testes  is  too  obvious  to  be  overlooked.  As  by  this  its  senso- 


FUNCTIONS   OF   THE   CEREBELLUM.  323 

ry  character  is  displayed,  so  the  same  holds  good  for  the  hemispheres, 
their  relations  with  the  spinal  cord  through  the  restiform  bodies  being 
also  of  a  sensory  nature.  It  seems  probable  that  the  superficial  vesicu- 
lar material  is  in  anatomical  connection  with  the  thalamus,  and  the  cor- 
pus dentatum  or  inner  ganglia  with  the  posterior  or  sensory  columns  of 
the  cord. 

The  arguments  which  have  been  brought  forward  by  those  who  sup- 
pose the  cerebellum  to  have  for  its  office  the  co-ordination  of  The  doctrine 
general  muscular  movement,  may  be  briefly  quoted  as  fol- 
lows  :  There  appears  to  be  a  general  correspondence  between  motion, 
its  size  and  the  degree  of  energy  and  complication  of  the  motor  powers 
in  various  animals.  Thus,  in  fishes,  and  likewise  in  birds,  those  tribes 
which  excel  in  their  powers  of  motion,  or  are  distinguished  by  the  com- 
plication of  their  movements,  are  characterized  by  the  manner  in  which 
this  organ  is  developed ;  and  the  same  may  be  said  even  of  the  mamma- 
lia, quadrupeds  whose  locomotive  mechanism  is  simple  possessing  it  in 
a  lower  state  of  development  than  those  which  either  temporarily  or 
constantly  move  on  the  posterior  extremities.  Among  apes,  those  which 
more  frequently  assume  the  erect  posture,  which  is  normal  to  man,  have 
their  cerebellum  of  a  size  more  closely  approaching  to  his. 

On  examining  such  facts,  it  appears  that  it  is  not  so  much  muscular 
power  as  the  quality  of  co-ordinating  and  governing  minute  muscular 
motions.  To  maintain  the  standing  position  motionless,  there  are,  in  re- 
ality, a  great  many  muscular  movements  required,  which  serve  to  antag- 
onize all  the  little  incidents  producing  a  tendency  to  fall ;  and  if  this  be 
so  in  standing,  how  much  more  difficult  must  such  antagonizing  and 
compensating  actions  become  in  walking,  running,  and  such  movements. 
Theoretically,  it  might  be  expected  that  some  special  organ  is  necessary 
to  combine  such  various  actions,  and  that  organ  seems  to  be  the  cere- 
bellum. 

In  confirmation  of  this  are  the  experimental  results  which  have  been 
obtained.  The  cerebellum,  on  irritation,  gives  rise  to  no  Results  of  ex- 
convulsive  motions,  nor  to  sensations.  If  removed  by  de-  ft"corebei^ 
grees  in  successive  slices,  the  motions  of  the  animal  become  lum. 
irregular,  and,  finally,  it  loses  all  power  of  walking  or  of  maintaining  its 
equilibrium.  Though  the  powers  of  the  animal  in  bringing  its  muscles 
into  contraction  seem  not  to  have  suffered,  it  can  not  co-ordinate  or  com- 
bine the  necessary  muscular  exertions,  and,  as  is  graphically  stated,  stag- 
gers and  falls  over  like  a  drunken  man,  still  making  efforts  to  maintain 
its  balance.  Such  experiments  have  been  repeatedly  made  in  the  case  of 
different  animals,  and  with  the  same  results. 

Connected  with  these  results  of  experimental  lesions  of  the  cerebellum 
are  the  rotations,  as  they  are  termed,  which  occur,  for  example,  when  one 


324  DOCTRINE  OF  PHRENOLOGY. 

Rotary  motions  of  the  crura  cerebelli  is  cut,  the  animal  rolling  upon  its  lon- 
of  animals.  gitudinal  axis  for  a  long  time  and  with  great  rapidity. 
From  such  facts,  it  has  therefore,  been  concluded  that  the  function  of  the 
cerebellum  is  neither  for  sensation  nor  intellection,  nor  is  it  the  source  of 
voluntary  movements,  but  that  it  is  for  the  government  or  control  of 
combined  muscular  action.  This  is  the  view  of  M.  Flourens. 

M.  Foville  supposes  that  the  cerebellum  is  for  the  perception  of  the 
Doctrine  that  sensations  derived  from  the  muscles,  and  enabling  the  mind 
cerebellum  is  to  exert  a  guiding  action.  The  facts  which  support  the  pre- 

for  the  percep-         ..  .  ,    ,,  .        -,         ,,  ,     .  .     •7,  . 

tion  of  muscu-  ceding  view  support  this  also,  there  being,  moreover,  in  this 
lar  sensations.  case?  an  additional  argument  derived  from  the  connection 
which  the  cerebellum  has  been  shown  to  maintain  with  the  sensory  col- 
umns of  the  cord,  and  the  pain  experienced  on  irritating  the  restiform 
columns.  It  has  likewise  been  pointed  out  that  this  hypothesis  illus- 
trates the  connection  between  the  cerebellum  and  the  optic  ganglia,  as  if 
it  were  for  the  purpose  of  bringing  the  organs  of  sight  to  the  aid  of  this 
co-ordination  of  muscular  motion. 

A  third  hypothesis,  to  which  allusion  has  been  made,  is,  that  the  cere- 
Doctrine  that  ke^um  *s  t^ie  organ  °f  sexual  instinct,  or  of  amativeness,  as 
it  is  the  organ  it  is  termed  by  phrenologists.  The  evidence  of  this,  when 
of  amativeness.  feidy.  examinea,  fe,  however,  very  far  from  affording  a  full 

proof;  indeed,  in  many  instances  the  facts  are  in  direct  opposition  to 
the  doctrine.  In  castrated  animals  the  cerebellum  undergoes  no  dimi- 
nution. There  is  no  coincidence  between  the  intensity  of  that  instinct 
in  the  different  animal  tribes  and  the  degree  of  development  of  this  or- 
gan ;  and  where  it  has  been  in  a  diseased  condition,  there  has  not  been  a 
necessary  correspondence  between  the  lesion  and  the  loss  of  the  instinct. 
This  view  of  the  function  of  the  cerebellum  is  connected  with  the  doc- 
trine of  special  localization,  or  phrenology,  which  may  therefore  bejiere 
briefly  considered ;  the  general  expression  of  this  doctrine  being  that  par- 
ticular regions  of  the  brain  are  devoted  to  special  functions, 
0  '  and  that  by  an  inspection  of  the  exterior  of  the  cranium  men- 
tal peculiarities  may  be  detected.  Drs.  Gall  and  Spurzheim  considered 
that  this  view  is  supported  by  the  fact  that  the  specialization  of  function 
in  the  brain  is  agreeable  to  the  general  mechanism  of  the  system,  in 
which  particular  organs  are  charged  with  particular  duties ;  that,  in  any 
individual,  the  mental  powers  are  not  equally  or  proportionally  developed, 
but  some  at  one  and  some  at  another  period  of  life,  and  so  likewise  of  their 
decline,  some  remaining  at  their  original  strength,  while  others  may  have 
Arguments  in  become  seriously  impaired.  It  does  not  appear  how  such 
Foc^zationof1  ^acts  can  ^e  explained  upon  the  hypothesis  that  the  whole 
functions.  brain  acts  as  a  unit.  They  may  be  readily  understood  if  it 
be  supposed  to  act  by  parts  which  are  developed  in  succession.  The 


WEIGHT  OP  THE   BRAIN.  325 

same  conclusion  is  arrived  at  from  well-known  facts  connected  with  in- 
sanity, in  which  it  very  frequently  happens  that  some  of  the  faculties 
alone  are  deranged,  while  the  others  retain  their  power,  and  some  may 
even  become  more  perfect  than  before ;  so,  likewise,  in  dreaming,  some 
of  the  faculties  retain  their  activity,  while  others  have  become  torpid ; 
and  so,  likewise,  when  different  individuals  are  compared,  some  exhibit  a 
superiority  in  one,  and  some  in  another  mental  particular ;  and  it  is  as- 
serted that  where  the  same  peculiarity  has  predominated  in  different  in- 
dividuals, it  has  always  been  attended  by  an  unusual  development  of  a 
special  locality  of  the  brain.  Nor  is  there,  in  these  views,  any  thing  that 
stands  in  contradiction  to  the  general  plan  upon  which  the  nervous  sys- 
tem itself  is  constituted,  as  is  manifested  by  the  different  sensory  gan- 
glia for  vision,  hearing,  or  smell,  or  the  arrangement  for  motion  or  sensa- 
tion presented  by  the  spinal  cord ;  and,  moreover,  they  are  supported  by 
the  comparative  anatomy  of  this  system ;  for,  whatever  grade  of  animal 
life  we  may  consider,  the  appearance  of  a  new  function  or  of  a  new  in~ 
stinct  is  certain  to  be  connected  with  a  new  and  contemporaneous  devel- 
opment of  some  part  of  the  nervous  system. 

The  facts  which  have  been  observed  in  cases  where  one  cerebral  hem- 
isphere has  either  suffered  lesions  or  lost  its  functions,  do  not  present 
any  contradiction  to  the  preceding  doctrines  ;  for,  though  the  remaining 
hemisphere  may  seem  to  act  equally  well  alone,  as  did  both  together,  we 
are  very  apt  to  deceive  ourselves  as  regards  the  actual  facts,  a  statement 
which  may  be  illustrated  by  recollecting  how  easily  we  persuade  our- 
selves that  we  see  with  one  eye  as  well  as  with  two.  No  doubt,  in  many 
of  the  ordinary  cases,  one  hemisphere  of  the  brain  may,  like  one  eye,  seem 
to  act  well  enough,  but  a  more  critical  examination  proves  that  in  other 
cases  this  is  far  from  being  true.  That  the  two  hemispheres  act  sever- 
ally and  separately  is  clear  from  what  sometimes  ensues  in  diseased  con- 
ditions of  one  of  them,  or  when,  perhaps,  there  is  a  want  of  symmetry 
between  them,  those  remarkable  forms  of  mental  derangement,  some- 
times known  under  the  designation  of  double  life  or  duality  of  mind, 
then  ensuing. 

In  man,  the  weight  of  the  brain  averages  about  fifty  ounces ;  in  fe- 
males, about  forty-five ;  the  maximum  being  about  sixty-four,  weight  of  the 
and  the  minimum  about  twenty ;  in  the  case  of  idiots,  the  brain- 
mean  specific  gravity  of  the  gray  matter  is  stated  by  Dr.  Sankey  to  be, 
in  both  sexes,  1.034,  but  somewhat  less  early  and  late  in  life.  The 
specific  gravity  of  the  white  is  1.041,  and  this  varies  less  with  sex  and 
time  of  life  than  the  former. 

The  functional  activity  of  the  brain  depends  on  the  copious  supply  of 
arterial  blood.  It  is  computed  that  one  fifth  of  the  whole  quantity  in 
the  circulation  is  sent  to  this  organ.  It  is  delivered  through  the  two 


326  PRESSURE  ON  THE  BRAIN. 

internal  carotid  and  two  vertebral  arteries.     The  impetus  of 

Supply  of  .11111- 

blood  "to  the  the  current  is  checked  Toy  the  sinuous  course  these  vessels 
brain-  take,  or  "by  their  breaking  promptly  into  capillary  branches. 

A  freedom  of  anastomosis  among  them,  as  is  well  displayed  in  the  circle 
of  Willis,  affords  abundant  provision  for  accidental  stoppages  or  re- 
straints. 

Although  the  brain  is  inclosed  in  an  unyielding  cavity,  it  is  subject  to 
Atmos  heric  ^  pressure  of  the  air,  a  fact  which,  though  it  has  been  de- 
pressure  on  the  nied  by  some  physiologists,  follows  from  ordinary  physical 
principles.  And  since  the  quantity  of  blood  present  at  any 
moment  in  the  organ  varies  with  the  contemporaneous  functional  activ- 
ity, being  greater  as  that  activity  is  greater,  the  cerebro-spinal  fluid  also 
varies  in  amount.  Through  this  fluid  an  equality  of  pressure  is  there- 
fore insured,  no  matter  what  may  be  the  quantity  of  blood  in  the  brain. 

The  cerebro-spinal  fluid,  the  quantity  of  which  has  been  estimated  at 
Cerebro-spinal  two  ounces,  is  readily  absorbed  and  as  readily  reproduced. 
fluid-  The  act  of  adjustment  between  it  and  the  blood  requiring  a 

certain  period  for  its  completion,  the  brain  can  not  instantaneously  be 
brought  to  its  maximum  action.  Thus,  as  all  persons  observe,  when  we 
undertake  any  unusual  intellectual  duty,  there  is  a  certain  preparatory 
period  to  be  passed  through,  as  the  common  expression  is,  "  for  compos- 
ing the  thoughts."  t 

Pressure  upon  the  brain,  either  applied  mechanically  or  through  acci- 
Effect  of  me-  dental  effusions,  produces  at  once  functional  inactivity,  prob- 


chanicai  pres-  a^j  ty  interference  with  the  due  circulation  of  the  blood  ; 
changes  in  the  and,  in  like  manner,  any  marked  change  in  the  chemical  re- 
blood.  lations  of  that  fluid  exerts  on  the  brain  a  corresponding  ef- 

fect. Thus,  when  oxygen  gas  is  breathed,  or,  still  better,  protoxide  of 
nitrogen,  which  is  more  soluble  in  the  blood,  the  processes  of  intellection 
go  on  in  an  exaggerated  way,  and  ideas  in  rapid  succession,  and  in  unu- 
sual forms  of  combination,  flit  through  the  mind  ;  but,  as  the  consequence 
of  this,  since  the  lungs  can  not  remove  with  the  necessary  promptness 
the  carbonic  acid  which  is  arising,  the  narcotic  effects  of  that  body  are 
soon  experienced  ;  and  this  is  also  the  case  in  alcoholic  intoxication,  in 
the  advanced  stages  of  which  the  accumulation  of  carbonic  acid  in  the 
blood  gives  rise  to  the  same  result. 

That  different  regions  of  the  brain  have  independent  though  mutually 
Effect  of  size  commissured  faculties,  is  fully  established  by  the  phenomena 
tion  onhe™"  °f  the  neryes  of  sense,  nor  can  there  be  any  doubt  that  these 
brain.  differences  of  physiological  function  are  directly  dependent  on 

differences  of  anatomical  structure.  It  is,  indeed,  to  structural  differences 
that  we  should  impute  the  greater  or  less  efficiency  of  the  whole  organ, 
as  much  as  to  differences  of  its  weight.  Because  of  a  higher  elaboration, 


DOUBLENESS  OP  THE  NERVOUS  SYSTEM.          327 

the  brain  of  one  person  may  be  more  energetic  than  that  of  another,  even 
though  its  weight  may  be  less.  It  is  not  to  be  denied,  however,  that  there 
is  a  connection  between  mental  power  and  the  quantity  of  cerebral  matter, 
when  individuals  of  the  same  kind  are  compared,  or  that  in  the  animal 
series  the  psychical  powers  decline  as  the  cerebrum  diminishes  in  size. 

Few  topics  are  more  worthy  of  the  attention  of  the  physiologist  than 
that  of  the  variable  psychical  powers  of  man,  and  yet  few  have  Ilg  variable 
been  more  overlooked.     By  variable  psychical  powers  I  mean  psychical . 
those  periodicities  of  increase  and  diminution  in  our  intellect-  p<rv 
ual  efficiency,  which  may  be  noticed  not  only  in  diseased,  but  abo  in 
healthy  states.     On  the  principles  we  have  presented,  these  find  their 
explanation  in  the  temporary  physical  states  of  the  organ,  such  as  its 
condition  of  repair,  its  existing  facility  for  oxidation,  and  the  constitution 
of  the  blood  as  respects  a  proper  arterialization. 

The  most  striking  structural  characteristic  of  the  nervous  system  is  its 
symmetrical  doubleness,  the  cranial  and  spinal  nerves  com-  Symmetrical 
ing  forth  by  pairs  to  their  distribution  on  the  right  and  left  ^l™™°{ 
sides  of  the  body.     The  manner  of  development  from  the  tem. 
spinal  axis  laterally  implies  such  a  construction,  and,  indeed,  gives  ori- 
gin to  two  halves  so  equal  and  alike  that  it  has  often  been  said  each 
person  consists  of  two  separate  individuals.     Examining  those  organs 
which,  by  reason  of  the  elaborateness  of  their  mechanism  and  principles 
of  action,  enable  us  to  determine  with  satisfactory  precision  Fun»ction  of 
the  function  discharged  by  each  one  of  the  members  of  the  each  lateral 
pair,  as  in  the  case  of  the  eye  or  the  ear,  we  may  corne  to  the  organ 
following  conclusions :  Each  is  a  distinct  organ  in  itself,  capable  of  its 
meeting  the  requirements  of  the  economy  in  a  sufficiently  satisfactory 
manner,  and  therefore  forms  a  distinct  whole ;  but  the  pair  can  likewise 
act  simultaneously,  re-enforcing,  to  a  certain  degree,  each  oth-  Con.ointl 
er's  power,  though  in  this  double  action  there  by  no  means   double  organs 
arises  a  double  intensity  of  effect.     The  closure  of  one  ear  jjj^j  £™J£ 
to  a  sound  does  not  diminish  the  loudness  by  one  half,  nor  crease 'their 
does  the  shutting  of  one  eye  reduce  to  one  half  the  bright-  pre' 
ness  of  a  light ;  but,  though  there  is  not  such  a  doubling  of  effect  when 
both  eyes  or  both  ears  are  employed,  there  is  a  degree  of  precision  in  the 
resulting  indication  which  is  not  to  be  gained  by  the  use  of  one  of  these 
organs  alone0     In  such  a  double  organ,  then,  the  result  is  not  so  much 
a  heightening  of  the  final  impression  as  the  giving  to  it  of  a  greater  de- 
gree of  precision. 

Moreover,  each  organ  seems  to  exert  a  compensating  influence  over  its 
fellow  in  any  deficiencies  or  imperfections  it  may  possess.  Compensation 
Tims  it  is  rare  that  both  eyes  are  of  an  equal  optical  good-  of  defects- 
ness,  as  most  individuals  wiH  find  on  making  a  personal  examination; 


• 
328  INDEPENDENT   ACTION   OF   EACH   HEMISPHERE. 

but  in  vision  with  both  eyes  the  faults  of  the  more  imperfect  one  are 
merged  in  the  indications  of  the  better,  and  the  same  might  be  remark- 
ed of  the  ear ;  from  which  it  would  appear  that  this  doubleness  of  or- 
gans is  rather  for  the  purpose  of  introducing  a  principle  of  compensation 
than  one  of  conspiring  action,  the  object  intended  to  be  gained  being  a 
justness  of  perception  rather  than  an  increase  of  effect. 

These  observations  apply  to  double  organs  in  their  normal  states,  or, 
Effect  of  tem-  if  not  their  normal,  their  habitual  ones ;  but  if  to  the  eye, 
porary  disturb-  fQY  example  a  temporary  disturbance  is  given,  as  by  press- 

anceofoneor-  f  .     ,         .        ,  ,.      °      ,       „  n 

gan.  ure  which  renders  its  optical  axis  oblique,  the  fellow  organ 

being  permitted  to  retain  its  usual  position,  double  sight  is  the  result. 
It  is  true  that,  in  the  habitual  divergence  of  strabismus,  such  is  not  the 
effect,  one  of  the  images  disappearing,  or  perhaps  the  mind,  accommodat- 
ing itself  to  the  habitual  condition,  combines  the  two  into  one.  These 
circumstances  indicate  that  each  member  of  a  double  organ  can,  under 
conditions  of  disturbance,  exercise  an  independent  and  even  opposing  ac- 
tion to  its  fellow. 

It  has  by  some  been  supposed  that  the  mind  pays  attention  to  the  im- 
The  indications  pressions  of  only  one  of  the  pair  of  organs  at  a  time ;  thus, 
contem°  fated  *^at  we  see  ^ie  ^mages  furnished  by  only  one  eye,  though  we 
at  a  time.  can  with  very  great  quickness  direct  attention  to  those  fur- 
nished by  the  other,  and  therefore,  deceived  by  the  rapidity  with  which 
this  alternation  of  attention  can  be  accomplished,  our  belief  in  the  syn- 
chronous use  of  both  organs  is  an  error.  If  two  differently  colored  ob- 
jects, such  as  differently  tinted  wafers,  be  so  placed  as  to  be  separately 
and  yet  simultaneously  viewed  by  both  eyes,  the  mind  vainly  attempts 
to  combine  the  two  images  together.  We  do  not  see  the  resulting  form 
of  a  green  tint,  but  we  see,  according  as  our  attention  is  given  to  the 
right  or  left,  a  blue  or  a  yellow,  if  these  have  been  the  colors  of  the  wa- 
fers, and  these  colors  can  quickly  merge  into  one  another,  like  dissolving 
Illustrative  views.  There  is  a  simple  experiment  which  serves  to  support 
experiment.  tm's  view,  and  which  any  one  may  readily  make.  If  the  open 
hand  be  placed  along  the  nose,  so  as  to  divide  the  right  eye  from  the  left, 
and  we  look  upon  the  surface  of  a  uniformly-illuminated  sheet  of  paper 
covered  with  writing,  it  will  be  found  that  we  can  only  read  with  one 
eye  at  a  time,  but  that  the  mind  can  with  great  rapidity  determine  which 
eye  it  will  use.  In  this  little  experiment,  we  have,  moreover,  the  means 
of  estimating  the  relative  sensitiveness  of  the  two  eyes,  and  other  of  their 
optical  peculiarities ;  thus  it  will  be  commonly  remarked  that,  though  the 
paper  be,  as  we  have  said,  uniformly  illuminated,  that  part  of  it  which  is 
regarded  by  one  eye  is  brighter  than  that  seen  by  the  other,  this  being 
due  to  a  difference  in  their  sensibility.  It  will  also  frequently  occur 
that  the  two  portions  of  the  page  will  present  different  shades  of  tint, 


DOUBLE  TRAINS  OF  THOUGHT.  329 

the  one,  perhaps,  being  a  faint  greenish  gray,  while  the  other  is  of  a  yel- 
lowish white,  the  proper  color  given  to  it  by  the  candle  or  lamp  Tby  which 
it  is  seen. 

In  this  feature  of  double  construction  the  brain  itself  participates,  pre- 
senting a  right  and  left  half  approaching  one  another  in  form,  without 
being  absolutely  identical.  Much,  therefore,  of  what  has  been  said  re- 
specting the  mutual  relations  of  the  right  and  left  eye,  and  the  right  and 
left  ear,  must  apply  to  the  right  and  left  hemispheres  of  the  brain ;  and 
it  is  under  this  point  of  view  that  Dr.  Wigan  has  regarded  it  in  Indc  endent 
his  work  on  the  Duality  of  the  Mind.  Nor  can  there  be  any  action  of  each 
doubt  that  each  hemisphere  is  a  distinct  organ,  having  the  hemisPhere- 
power  of  carrying  on  its  functions  independently  of  its  fellow;  that,  though 
each  can  thus  act  separately,  both  can  act  simultaneously ;  and,  judg- 
ing from  the  cases  that  have  just  been  presented,  it  would  seem  that  we 
are  justified  in  inferring  that  the  common  action  of  the  two  hemispheres 
is  not  for  the  purpose  of  a  heightening  of  effect,  but  only  for  greater  pre- 
cision, and  that  in  the  same  manner  as  it  is  a  rare  thing  to  find  two  eyes 
or  two  ears  of  equal  goodness,  so  also  it  is  unusual  to  have  two  hemi- 
spheres which  are  precisely  alike.  The  defects  of  the  one  may  insubor<jina- 
be  compensated  by  the  superiorities  of  the  other,  and  thus  tion  of  one 
a  mean  result  be  attained ;  and  as  one  eye  or  one  ear  can, 
under  the  proper  circumstances,  overpower  its  fellow,  so  likewise  can  one 
hemisphere  of  the  brain,  except  in  certain  cases,  which  have  been  some- 
what imaginatively  described  as  insubordination  of  one  of  the  hemi- 
spheres, when  insanity  is  the  result,  the  healthy  half  being  unable  to 
control  the  diseased  one ;  and  for  this  reason,  we  often  observe  of  the 
insane  that  they  have  synchronously,  or,  at  all  events,  in  a  very  rapid  al- 
ternation, two  distinct  trains  of  thought,  and,  consequently,  Double  train  of 
two  distinct  utterances,  each  of  which  may,  so  to  speak,  be  thousht- 
perfectly  continuous  and  even  sane  by  itself,  but  the  incongruities  that 
arise  from  the  mingling  of  the  two  betray  the  condition  of  such  persons. 
In  fhis  case  doubleness  of  action  is  seen  in  its  most  exaggerated  aspect, 
but  in  a  less  degree,  it  may  be  remarked,  in  the  thinking  operations  of 
those  whose  minds  are  perfectly  sound.  Thus  there  is  no  student  but 
must  have  observed,  when  busily  engaged  in  reading,  that  his  mind  will 
wander  off  to  other  things,  though  he  may  mechanically  cast  his  eyes 
over  page  after  page ;  and  the  same  may  occur  in  listening  to  a  lecture 
or  sermon.  But,  though  the  insane  man  may  indulge  in  two  synchro- 
nous trains  of  thought,  he  never  indulges  in  three,  for  the  simple  reason 
that  he  has  not  three  hemispheres  to  do  it  with,  the  same  remark  apply- 
ing to  the  sane  man  in  the  accidental  wanderings  of  his  thoughts. 

The  overcoming  of  this  insubordination  of  one  of  the  hemispheres  may, 
to  a  very  considerable  degree,  be  accomplished  by  education,  of  which 


330  CASTLE-BUILDING. 

Effect  of  edu-  one  of  the  chief  results  is  that  it  exercises  us  in  the  habit  of 
cation.  thinking  of  one  thing  at  a  time,  of  thinking  therefore  with- 

out confusion,  and  of  arriving  at  conclusions  with  precision  and  decision. 
And  these  considerations  should  also,  in  Dr.Wigan's  view,  be  our  chief 
guide  in  the  cure  of  insanity,  doing  all  in  our  power  to  invigorate  the  ac- 
tion of  the  healthy  hemisphere,  and  enable  it  to  subdue  the  insubordina- 
tion of  the  diseased  one.  If  both  hemispheres  are  diseased,  the  case  is 
almost  hopeless. 

Of  the  independent  and  yet  complete  action  of  each  of  the  cerebral  hem- 
Perfect  action  isPneres  we  ^ave  abundant  and  interesting  proof.  Mental 
of  a  single  operations  can  be  carried  on  in  a  profoundly  diseased  state  of 
hemisphere.  Qne  Qf  fi^Q  organs,  as  multitudes  of  well-authenticated  cases 
attest — nay,  even  when  the  lesion  has  gone  so  far  as  to  amount  to  an 
absolute  and  entire  disorganization  of  one  of  the  hemispheres.  Similar 
evidence  is  also  furnished  by  those  interesting  cases  in  which,  by  accident, 
as  by  gunshot  wound,  destruction  of  one  side  has  occurred. 

Even  in  a  state  of  health  we  have  numerous  examples  of  this  inde- 
Intermixed  ac  Pen^ent  action  of  each  hemisphere.  While  engaged  in  ordi- 
tion  of  the  two  nary  pursuits  which  imply  a  continued  mental  occupation, 
hemispheres.  we  afe  occasiona]iy  troubled  with  suggestions  of  a  different 
kind.  A  strain  of  music,  or  even  a  few  notes,  may  be  perpetually  ob- 
truding, and  such  an  occurrence  we  could  scarcely  explain  save  upon  the 
principle  of  the  separate  action  of  these  organs,  the  one  interfering  with 
the  other.  That  precision  which  we  have  remarked  as  arising  from  the 
conjoint  use  of  two  eyes  and  two  ears  is  doubtless  also  attained  where 
the  two  hemispheres  are  acting  in  unison.  We  can,  moreover,  volunta- 
rily permit  one  to  rest  while  the  other  continues  its  duty,  as  we  can  vol- 
untarily make  use  of  one  eye,  disregarding  the  indications  of  the  other ; 
but  where  it  is  necessary  to  execute  a  critical  comparison  or  arrive  at  an 
accurate  judgment  of  things,  both  hemispheres  are  brought  into  action, 
as  are  both  eyes  when  we  intently  consider  an  object. 

Among  other  phenomena,  Dr.  Wigan  calls  attention  to  the  operation 
Castle-  of  castle-building,  as  it  is  designated,  as  illustrating  the  volunta- 
buiidmg.  ry  manner  in  which  we  permit  one  hemisphere  to  act,  presenting 
fanciful  delusions ;  the  other,  as  it  were,  watching  with  satisfaction  the 
operation,  and  in  this  respect  lending  itself  to  it.  Not  that  for  a  moment 
we  suppose  there  is  any  truth  in  the  ideas  suggested,  and  in  this  the 
phenomenon  differs  essentially  from  that  of  dreaming,  in  which  it  never 
occurs  to  us  that  the  scenes  and  actions  are  unsubstantial. 

Still  more  strikingly  do  those  singular  cases,  which  from  time  to  time 
Double  or  ai-  Present  themselves  to  the  physician,  of  double  or  alternate 
ternate  con-  consciousness,  illustrate  this  isolated  function  of  the  hemi- 
spheres. In  some  of  these,  which  have  been  carefully  ob- 


SENTIMENT   OP  FEE-EXISTENCE.  331 

served  and  authentically  recorded,  each  of  these  portions  of  the  brain  has 
continued  its  action  for  a  period  of  days,  or  even  weeks,  and  then,  relaps- 
ing into  a  quiescent  state,  has  been  succeeded  by  the  other,  thus  present- 
ing in  some  degree  an  analogy  of  what  is  observed  in  ordinary  cases  of 
insanity,  so  far  as  the  reciprocating  action  of  the  two  organs  is  concerned, 
but  differing  in  the  period  of  duration  of  their  function  ;  and  thus,  if  one 
of  them  should  have  undergone  deterioration,  or  have  suffered  lesion,  so 
that  it  has  been  reduced  to  what  might  be  termed  an  infantile  state,  the 
impressions  formerly  stored  up  in  it  having  been  for  the  most  part  lost, 
or  there  being  an  incapacity  in  it  to  make  use  of  them,  the  patient  will 
alternately  exhibit  what  has  been  aptly  termed  child  life  and  mature  life. 
For  a  few  days,  or  perhaps  weeks,  he  will  conduct  himself  in  the  ordi- 
nary manner  of  an  adult,  reading,  reasoning,  and  acting,  and  then,  for  a 
similar  period,  will  pass  into  a  condition  in  which  he  does  not  even  know 
his  letters,  and  reasons  and  acts  like  a  child.  These  phenomena  of  al- 
ternate and  double  intellection  are  interesting  in  the  highest  degree,  and 
seem  to  be  explicable  on  no  other  principle  than  that  which  this  author 
suggests. 

But  I  do  not  think  that  the  explanation  which  he  offers  of  the  senti- 
ment of  pre-existence  is  correct.  By  this  term  is  under-  Sentiment  of 
stood  that  strange  impression,  which  all  persons  have  occa-  Pre-existence. 
sionally  observed  in  the  course  of  their  lives,  that  some  incident  or  scene 
at  the  moment  occurring  to  them,  it  may  be  of  quite  a  trivial  nature, 
has  been  witnessed  by  them  once  before,  and  is  in  an  instant  recognized. 
Though  this  opinion  that  we  have  seen  a  present  incident  once  before 
sometimes  occurs  in  cases  where  the  circumstances  are  of  profound  in- 
terest to  us,  the  experience  of  most  persons  assures  us  that  it  is  more  fre- 
quently in  trivial  events.  Dr.  Wigan's  view  is,  that  it  arises  from  the 
almost  contemporaneous  action  of  the  two  hemispheres,  and  that,  under 
the  circumstances,  we  have  a  confusion  of  memory,  and  are  led  to  be- 
lieve that  there  has  been  an  interval  of  indefinite  duration,  when,  in 
point  of  fact,  it  was  an  impression  in  each  hemisphere  closely  coincident 
in  point  of  time.  This  explanation  turns  on  the  assumption  that  this 
sentiment  of  pre-existence  occurs  but  once.  He  denies  that  we  ever 
suppose  that  we  have  seen  the  thing  twice  before.  But  I  believe  that 
the  experience  of  many  individuals  assures  them  that  this  is  not  the  case, 
,  and  that  they  are  under  a  firm  persuasion  that  they  have  witnessed  the 
same  incidents  more  than  once  before,  nay,  perhaps  even  many  times. 
The  instance  which  this  author  furnishes  as  occurring  to  himself,  in 
which,  on  the  occasion  of  attending  the  funeral  of  an  exalted  personage, 
and  at  the  time  of  the  coffin  being  deposited  in  the  vault,  with  the  strik- 
ing solemnities  of  the  occasion  there  rushed  upon  his  mind  the  idea  that 
he  had  been  present  at  this  same  scene  once  before,  a  thing  which  was, 


332  LOSS   OF   PERCEPTION   OF   TIME. 

of  course,  an  impossibility,  is  very  instructive.  But  the  difficulty  in  the 
way  of  his  hypothesis  lies  in  the  fact  that  it  offers  us  no  explanation  of 
those  cases  in  which  we  are  perfectly  persuaded  that  we  have  witnessed 
the  thing  more  than  once  before,  though  it  may  answer  in  the  particular 
Loss  of  a  true  ins*ance  here  cited.  Perhaps  we  may  appropriately  recall  the 
perception  of  well-known  fact  offered  to  us  in  dreaming,  and  to  which  at- 
tention hereafter  will  be  more  particularly  directed,  that  there 
are  circumstances  under  which  our  mental  operations  are  carried  forward 
with  the  most  marvelous  speed.  Thus  a  sudden  sound,  which  awakes 
us,  or  even  a  flash  of  lightning,  which  is  over  in  a  moment,  may  be  in- 
corporated or  expanded  into  a  long  dream,  diversified  with  a  various 
multitude  of  incidents,  all  appearing  to  follow  one  another  in  an  appro- 
priate order,  and  occupying,  as  we  judge,  quite  a  long  time,  yet  all  nec- 
essarily arising  in  an  instantaneous  manner,  for  we  awake  at  the  moment 
of  the  disturbance.  Of  the  same  kind  is  that  remarkable  deception, 
which  is  authentically  related  by  those  who  have  recovered  from  death 
by  drowning,  that  in  the  last  moment  of  their  agony  all  the  various 
events  of  their  past  life,  even  those  of  a  trivial  kind,  have  come  rushing 
before  them  with  miraculous  clearness.  Mental  operations,  therefore, 
both  as  regards  old  recollections  and  new  suggestions,  may  take  effect 
with  wonderful  rapidity,  and  if  the  sentiment  of  pre-existence  is  to  be 
explained  on  the  principle  of  the  double  action  of  the  brain,  it  must  like- 
wise be  dependent  upon  the  fact  here  presented. 


THE   CRANIAL    NERVES.  333 


CHAPTER  XVII. 

OF  THE  CRANIAL  NERVES  AND  THE  GREAT  SYMPATHETIC. 

Enumeration  of  the  Cranial  Nerves. —  The  Third  Pair,  or  Oculo-motor. —  The  Fourth  Pair,  orPa- 
thetid. — The  Fifth  Pair,  or  Trigemini. —  The  Sixth  Pair,  or  Abducentes. — Illustrations  of  the 
Third,  Fourth,  Fifth,  and  Sixth  Pairs. — The  Seventh  Pair,  or  Facial. — Illustration  of  the 
Facial. — The  Ninth  Pair,  or  Glosso-pharyngeal. — Illustration  of  the  Glosso-pharyngeal. — The 
Tenth  Pair,  or  Pneumogastric. — Illustration  of  the  Pneumogastric. — Illustration  of  the  Laryn- 
geals. — The  Eleventh  Pair,  or  Spinal  Accessory. — The  Twelfth  Pair,  or  Hypoglossal. — Il- 
lustration of  the  Hypoglossal. 

The  Phrenic  Nerve. 

Of  the  Great  Sympathetic  System. — Position,  Structure,  and  Origin  of  the  Sympathetic. — Its  Re- 
lation with  the  Pneumogastric. — Its  Connection  with  the  Spinal  System. — Its  Plexuses. — Its 
Ganglia. — They  are  Reservoirs  of  Force. — Summary  of  the  Functions  of  the  Sympathetic. — 
Illustration  of  the  Sympathetic. —  The  Abdominal  Plexuses. — The  Solar  Plexus. — The  Mesen- 
teric  Plexuses. 

THERE  are  twelve  pairs  of  cranial  nerves :  1st.  The  olfactory;  2d.  The 
optic ;  3d.  The  oculo-motor ;  4th.  The  pathetic ;  5th.  The  tri-  The  cranial 
facial;  6th.  The  abducent ;  7th.  The  facial;  8th.  The  audito-  nerves- 
ry  ;  9th.  The  glosso-pharyngeal ;   10th.  The  pneumogastric ;  llth.  The 
spinal  accessory ;  12th.  The  hypoglossal. 

Of  these,  the  first,  the  second,  and  the  eighth,  being  nerves  of  special 
sensation,  may  be  more  conveniently  studied  in  connection  with  the  or- 
gans of  special  sense — the  nose,  the  eye,  the  ear. 

OF   THE   THIRD  PAIR,  OR   OCULO-MOTOR  NERVES. 

The  motor-oculi  nerve  arises  from  the  inner  side  of  the  crus  cerebri', 
near  to  the  pons  varolii,  some  of  its  fibres  passing  into  the  The  third  pair, 
gray  substance  of  the  crus.  Advancing  forward,  it  divides  or  oculo-motor. 
into  two  branches,  one  of  which  supplies  the  superior  rectus  andlevator 
palpebrae,  the  other  the  internal  rectus,  inferior  rectus,  and  inferior  ob- 
lique. Considering  the  place  of  origin,  it  would  be  expected  that  this 
nerve  is  wholly  motor,  and  this  is  confirmed  by  experiment.  When  the 
nerve  is  irritated  the  muscles  which  it  supplies  are  convulsed,  and  when 
it  is  divided  they  are  paralyzed.  Through  its  connection  with  the  len- 
ticular ganglion,  it  furnishes  motor  filaments  to  the  iris.  The  optic 
nerve,  the  corpora  quadrigemina,  and  this  nerve  together  constitute  a 
complete  nervous  arc,  and  impressions  made  on  the  retina  occasion  mo- 
tions in  the  iris. 


334  THE   FOURTH,   FIFTH,   AND   SIXTH   PAIRS. 

OF  THE  FOURTH  PAIR,  PATHETICI,  OR  TROCHLEAR  NERVES. 

This  nerve  arises  from  the  valve  of  Yieussens,  near  the  testis,  and, 
The  fourth  pair,  passing  around  the  cms  cerebri,  enters  the  orbit,  and  is  dis- 
or  pathetic!.  tributed  to  the  orbital  surface  of  the  superior  oblique,  or 
trochlear  muscle,  for  which  it  is  the  motor  nerve.  When  it  is  irritated 
that  muscle  is  convulsed. 

OF   THE   FIFTH  PAIR,  TRIFACIAL,  OR   TRIGEMINI. 

The  fifth  nerve  has  a  construction  so  closely  analogous  to  that  of  the 
The  fifth  pair,  spinal  nerves,  that  it  has  been  designated  the  spinal,  nerve  of 
or  trigemini.  ^he  head.  It  arises  by  two  roots,  the  anterior  of  which  is 
the  smaller,  the  posterior  having  a  large  ganglion,  the  ganglion  of  Gas- 
ser ;  with  this  ganglion  the  anterior  root  is  in  contact,  but  not  in  con- 
nection: it  passes  forward  to  the  inferior  maxillary  nerve.  From  the 
ganglion  three  branches  diverge,  the  ophthalmic,  the  superior  maxillary, 
and  inferior  maxillary,  the  first  proceeding  from  the  upper  angle  of  the 
ganglion,  the  second  from  the  middle,  the  third  from  the  inferior  angle. 
This  last  receives  the  motor  portion  of  the  nerve ;  the  first  and  second 
branches  are  sensory,  the  third  is  sensory  and  motor  also.  From  the 
sensory  portions  the  anterior  and  most  of  the  antero-lateral  portions  of 
the  head  are  furnished,  as  also  the  organs  of  special  sense  themselves,  so 
far  as  their  common  sensation  is  concerned.  The  motor  branch  supplies 
the  muscles  of  mastication. 

OF   THE    SIXTH  PAIR,  OR  ABDUCENTES. 

This  nerve  arises  by  several  filaments  from  the  upper  part  of  the  cor- 
The  sixth  pair,  pus  pyramidale,  near  to  the  pons  varolii,  and  is  distributed 
or  abducentes.  to  tne  external  rectus.  From  its  origin,  distribution,  and 
from  experiments  made  upon  it,  it  is  known  to  be  a  motor  nerve. 

ILLUSTRATIONS   OF   THE   THIRD,  FOURTH,  FIFTH,  AND   SIXTH  PAIRS   OF   NERVES. 

Fig.\§\\  1,  chiasm  of  optic  nerves;  2, 
third  pair ;  3,  nasal  nerve ;  4,  external  oculo- 
motor; 5,  ganglion  of  Gasser;  6,  nasal  nerve 
and  its  two  branches,  internal  and  external ; 
7,  nerve  of  obliquus  inferior ;  8,  ophthalmic 
ganglion ;  9,  ciliary  nerves  ;  #,  portion  of  ld- 
vator  palpebrae  superioris  and  rectus  superi- 
or ;  £,  rectus  inter  nus ;  c,  rectus  extern  us ;  d, 
fibrous  ring  of  the  recti  muscles. 

NERVES   IN  THE   ORBITAL   CAVITY. 

NemTs  of  the  orbit.  Fig.  162  i  1, 1,  optic  nerve  and  globe  of  the 


THE   FIFTH   NERVE. 


335 


Fig.  162. 


8     7    dJO    b 

Nerves  in  the  orbital  cavity. 


eye;  2, third  nerve ;  3,  superior  branch ; 
4,  nerve  of  obliquus  inferior;  5,  external 
oculo-motor ;  6,  ganglion  of  Gasser ;  7, 
ophthalmic  branch ;  8,  nasal  nerve ;  9, 
ophthalmic  ganglion;  10,  short  root  of 
ophthalmic  ganglion;  11,  ciliary  nerves ; 
12,  frontal  nerve ;  #,  levator  palpebras 
superioris  and  rectus  superior ;  Z>,  rectus 
inferior  ;  c,  obliquus  inferior ;  d,  rectus 
extemus  ;  e,  ring  of  the  recti  muscles. 


DIAGRAM   OF   THE   FIFTH  NERYE. 


Fig.  163. 


Fig.  163 :  1,  ganglion  of  Gasser ; 
2,  ophthalmic  ganglion ;  3,  its  long 
root  furnished  by  the  nasal  branch; 
4,  short  root ;  5,  sympathetic,  from 
the  plexus  surrounding  the  inter- 
nal carotid ;  6,  ciliary  nerves  trav- 
ersing the  sclerotic ;  7,  ciliary  gan- 
glion ;  8,  ganglion  of  Meckel ;  9, 
its  sensory  roots  from  the  superior 
maxillary ;  10,  petrous  branch  of 
vidian  nerve,  or  motor  root  of  the 
ganglion  of  Meckel ;  11,  its  sym- 
pathetic root ;  12,  naso- palatine 

Diagram  of  the  fifth  nerve.  ganglion,  receiving  at  its  upper  an- 

gle the  naso-palatine  nerve,  and  at  its  inferior  the  anterior  palatine ;  13, 
otic  ganglion  ;  14,  small  superficial  petrosal ;  15,  submaxillary  ganglion ; 
16,  sublingual  ganglion ;  17,  geniculated  ganglion;  18,  cavernous  ganglion. 


GANGLION  OF  GASSER  AND  ADJACENT  PARTS. 

Fig.  164.  _  Fig.  164 :    1,  ganglion   of  Gas- 

ser; 2,  ophthalmic  nerve;  3,  front- 
al branch  ;  4,  lachrymal ;  5,  nasal ; 
6,  opthalmic  ganglion;  7,  superior 
maxillary  nerve  ;  8,  orbital  branch ; 
9,  ganglion  of  Meckel ;  10,  petrosal 
branch  of  vidian  nerve;  11.  palatine 
nerves ;  12,  anastomosis  of  the  gan- 
glion *of  Meckel  with  the  nervous 
plexus  surrounding  the  internal  max- 
illary artery ;  13,  posterior  and  su- 
perior dental  nerves ;  14,  suborbital  nerve,  its  anastomoses  with  facial 


Ganglion  of  Gasser. 


336 


THE   FIFTH   NERVE. 


and  nasal;  15,  inferior  maxillary,  receiving  the  motor  portion  of  the  fifth 
pair  ;  16,  superficial  auriculo-temporal  nerve  ;  17,  buccal  nerve  ;  18,  sec- 
tion of  other  collateral  branches  of  inferior  maxillary  ;  19,  inferior  den- 
tal ;  20,  mental  nerve  ;  21,  lingual  ;  22,  chorda  tympani  ;  23,  facial 
nerve  ;  A,  external  carotid  artery  ;  B,  facial  artery  ;  C,  temporal  artery  ; 
D,  internal  maxillary  ;  E,  its  dental  branch  ;  F,  middle  meningeal  ;  a, 
membrana  tympani  ;  #,  glenoid  cavity  ;  <?,  orbicularis  oris  ;  d,  buccina- 
tor ;  £,  pterygoideus  internus  ;  /,  pterygoideus  externus  ;  g,  digastric  ; 
h  sterno-cleido-mastoid  muscle. 


THE   FIFTH  NERVE,  THE   GANGLION   OF   GASSER   BEING   REMOVED. 

Fig.  165.  Fig.  165  :  1,  ophthalmic,  cut  ;  2, 

superior  maxillary,  cut  at  both  ex- 
tremities ;  3,  ganglion  of  Meckel  ;  4, 
petrosal  and  carotid  branch  of  vidian 
nerve  ;  5,  abducent  ;  6,  nerve  of  Ja- 
cobson  ;  7,  superior  and  posterior 
dental  nerves  ;  8,  anterior  and  supe- 
rior dental  nerve  ;  9,  otic  ganglion  ; 
10,  gustatory  nerve  ;  11,  chorda  tym- 
pani ;  12,  submaxillary  ganglion  ; 
13,  anastomosis  of  lingual  with  hy- 
poglossal  ;  14,  sublingual  plexus  ;  15,  terminal  branches  of  gustatory  or 
lingual  nerve  ;  16,  inferior  dental  ;  17,  mylo-hyoid  branch  ;  18,  mental  ; 
19,  incisive  nerve  ;  20,  ganglion  of  glosso-pharyngeal  ;  21,  facial,  in  the 
aqueduct  of  Fallopius  ;  22,  hypoglossal  ;  a,  superior  maxillary  bone  ;  b, 
cartilages  of  the  nose  ;  £,  internal  wall  of  tympanic  cavity  ;  d,  ptery- 
goideus internus  muscle  ;  £,  buccinator,  cut  ;  y,  mylo-hyoid  muscle  ;  g, 
part  of  anterior  belly  of  digastric  ;  A,  sterno-cleido-mastoid,  turned  aside. 


The  fifth  nerve. 


ILLUSTRATION   OF  THE  TERMINAL   BRANCHES   OF  THE 
INFERIOR  MAXILLARY  NERVE. 

Fig.  166  :  1,  motor  and  sensory  roots 
of  ganglion  of  Gasser ;  2,  junction  of  mo- 
tor root  with  inferior  maxillary;  3,  auricu- 
lo-temporal nerve ;  5,  buccal  nerve ;  6, 
pterygoid  nerves ;  7,  cut  branches  of  tem- 
poral and  masseteric  nerves ;  8,  gustatory 
nerve;  9,  chorda  tympani;  10,  facial;  11, 
anastomosis  of  gustatory  and  inferior  den- 
tal nerves ;  12,  tonsillar  branch ;  13,  sub- 

The  inferior  maxiiiary.  maxillary  ganglion ;  14,  sublingual  plex- 

us; 15,  anastomosis  of  gustatory  and  hypoglossal  nerves;  16,  branches 


THE   FACIAL   NERVE. 


337 


of  gustatory;  17,  inferior  dental;  18,  mylo-hyoid  nerve;  19,  incisive 
branch  of  dental  nerve;  20,  branch  of  mental,  cut;  <z,  pterygoideus  in- 
ternus  ;  b,  part  of  pterygoideus  externus  muscle ;  c,  mylo-hyoid  muscle ; 
d,  portion  of  anterior  belly  of  the  digastric ;  e,  hypoglossal  muscle  ;  J\ 
portion  of  submaxillary  gland. 

OF   THE    SEVENTH  PAIR,  THE   FACIAL  NERVE. 

This  nerve  arises  from  the  upper  part  of  the  groove  between  the  oli- 
vary and  restiform  bodies,  and  near  the  pons.  varolii.  With  The  seventh 
the  auditory  nerve,  or  portio  mollis,  it  constitutes  the  seventh  Pair> or  facial, 
nerve  in  the  nomenclature  of  Willis,  and  derives  the  name  portio  dura, 
under  which  it  sometimes  passes,  from  the  density  and  closeness  of  its 
texture.  It  supplies  all  the  muscles  of  the  face  except  those  of  mastica- 
tion, which  are  supplied  by  the  fifth  nerve,  those  of  the  palate,  the  sta- 
pedius,  laxator  tympani,  and  tensor  tympani ;  also  the  muscles  of  the  ex- 
ternal ear,  and  some  of  those  of  the  tongue.  The  facial  is  a  centrifugal 
nerve.  If  irritated  near  its  origin,  there  is  no  sensation  of  pain ;  but  sub- 
sequently it  obtains  fibres  from  other  sources,  as  from  the  fifth  and  the 
pneumogastric.  After  it  has  been  joined  by  these,  irritation  is  acutely 
felt.  It  is  therefore  to  be  regarded  as  the  general  motor  nerve  of  the 
face,  influencing  the  function  of  respiration  through  reflex  action,  but  not 
being  connected  with  the  function  of  mastication.  Injury  of  it  produces 
paralysis  of  the  parts  to  which  it  is  distributed,  as,  for  example,  the  orbic- 
ularis  palpebrarum,  causing  inflammation  of  the  eye  and  opacity  of  the 
cornea,  through  inability  of  that  organ  to  free  itself  from  dust  and  spread 
the  lachrymal  secretion  over  its  surface.  In  like  manner,  the  sense  of 
hearing  may  be  injured  through  loss  of  control  over  the  muscular  struc- 
tures of  the  ear,  and  the  acuteness  of  the  sense  of  smell  diminished  from 
Fig.iw.  inability  to  introduce  the  air  in  a 

strong  current,  or  the  sense  of  taste, 
if  the  point  of  injury  be  previous  to 
the  giving  off  of  the  chorda  tympani. 
In  paralysis  of  the  facial  nerve  the 
muscles  of  the  face  become  powerless, 
and  the  countenance,  therefore,  dis- 
torted. 


ILLUSTRATION  OF   THE   FACIAL  NERVE. 

Fig.  167 :  1,  trunk  of  the  facial 
at  its  emergence  from  the  aqueduct 
of  Fallopius  ;  2,  occipito- auricular 
branch ;  3,  auricular  of  the  cervical 
plexus  ;  4,  twig  of  the  occipital  mus- 


The  facial  nerve. 


338  THE    GLOSSO-PHARYNGEAL   NERVE. 

cle ;  5,  twig  of  the  posterior  auricular  muscle ;  6,  twig  of  the  superior 
auricular ;  7,  anastomosis  of  the  facial  with  the  auricular  of  the  cervical 
plexus  ;  8,  branch  for  the  stylo-hyoid  and  posterior  belly  of  the  digastric ; 
9,  temporo-facial  anastomosis  with  the  superficial  auriculo-temporal  of 
the  fifth  pair ;  10,  temporal  ramifications  of  the  facial ;  11,  frontal  twigs  ; 
12,  superior  palpebral  twigs  ;  13,  middle  palpebral  twigs ;  14,  inferior 
or  motor  palpebral  twigs;  15,  suborbital  twigs  ;  16,  suborbital  plexus; 
17,  superior  buccal;  18,  cervico-facial  branch;  19,  buccal  branches,  anas- 
tomosing'with,  20,  buccal  nerve  of  fifth  pair;  21,  mental  twigs,  forming 
with,  22,  mental  nerve  of  fifth  pair,  the  mental  plexus ;  23,  cervical 
branches  ;  24,  transverse  cervical  branch  of  cervical  plexus  ;  25,  parotid 
branches  of  the  superficial  auriculo-temporal ;  26,  parotid  branches  of  the 
facial ;  #,  frontal  muscle ;  b,  occipital  muscle ;  c,  anterior  auricular ;  d, 
superior  auricular ;  0,  posterior  auricular;  f,  orbicularis  palpebrarum;  ^, 
zygomaticus,  major  ;  -A,  buccinator ;  ^orbicularis  oris  ;  &,  masseter;  £, 
parotid  gland ;  m,  platysma ;  n,  stylo-hyoid  and  posterior  belly  of  di- 
gastric ;  o,  sterno-cleido-mastoid ;  j?,  trapezius. 

OF   THE   NINTH   PAIR,  OR   GLOSSO-PHARYNGEAL. 

This  nerve  arises  by  five  or  six  filaments  from  the  groove  between 
The  ninth  pair,  ^ie  0^var7  an^  restiform  bodies.  Its  origin  may  be  traced 
or  giosso-pha-  to  the  vesicular  substance  in  the  floor  of  the  fourth  ventricle : 
passing  forward,  it  is  distributed  to  the  mucous  membrane 
of  the  base  of  the  tongue  and  fauces.  While  in  the  jugular  fossa  it 
forms  two  ganglia,  a  small  one  produced  by  its  posterior  fibres,  and  call- 
ed the  superior  ganglion  ;  a  second,  much  larger,  termed  the  inferior,  or 
ganglion  of  Andersch.  The  branches  given  off  by  the  glosso-pharyngeal 
are  the  muscular,  the  tympanic  or  Jacobson's  nerve,  which  is  distributed 
to  the  inner  wall  of  the  tympanum  and  interior  portions  of  the  ear ;  the 
pharyngeal,  which  supplies  the  pharynx,  and,  with  branches  of  the  pneu- 
mogastric  and  sympathetic,  forms  the  pharyngeal  plexus ;  the  lingual 
supplies  the  mucous  membrane  of  the  sides  and  base  of  the  tongue ; 
the  tonsillitic,  which  supplies  the  mucous  membrane  of  the  fauces  and 
soft  palate,  and  forms  a  plexus  round  the  base  of  the  tonsil.  Besides 
these,  the  glosso-pharyngeal  anastomoses  with  the  facial,  pneumogastric, 
accessory,  and  sympathetic. 

Examined  in  the  usual  way,  the  glosso-pharyngeal  proves  to  be  a  cen- 
tripetal nerve,  having  the  power  of  producing  reflex  motions  through  the 
nerves  of  deglutition,  its  motor  influence  being  chiefly  due  to  its  con- 
nections with  the  pneumogastric  and  accessory.  Though  thus  a  sen- 
sory nerve,  it  is  doubtful  whether  it  be  the  only  nerve  of  taste,  or  whether 
that  function  is  not  likewise  participated  in  by  the  lingual  branch  of  the 
fifth  pair.  It  is  certain  that  section  of  the  lingual  does  not  destroy  the 


THE   GLOSSOPHARYNGEAL   NERVE. 


339 


sense  of  taste,  and  also  that  those  parts  of  the  tongue  to  which  the 
glosso-pharyngeal  is  distributed  present  that  sense  in  the  most  marked 
manner.  The  inference  which  is  usually  drawn  is  that  this  nerve  and  the 
lingual  are  both  tactile  and  gustative,  and  this  renders  appropriate  its 
description  in  this  place  rather  than  among  the  nerves  of  special  sense. 


ILLUSTRATION  OF   THE   GLOSSO-PHARYNGEAL. 


Fig.  168. 


Fig.  168 :  1,  origin  of  the  glosso-pharyngeal 
between,  2,  the  pneumogastric,  and,  3,  the  facial.; 
4,  ganglion  of  Andersch;  5,  pharyngeal  branches; 
6,  anastomosis  of  the  glosso-pharyngeal  with  the 
lingual  branch  of  the  facial ;  7,  application  of  the 
spinal  to  the  superior  ganglion  of  the  pneumo- 
gastric ;  8,  branch  of  jugular  fossa ;  9,  plexiform 
ganglion  of  par  vagum  ;  10,  carotid  branch ;  11, 
superior  laryngeal  nerve ;  12,  external  laryngeal; 
13,  inferior  or  recurrent  laryngeal ;  14,  cervical 
branch  of  the  spinal ;  15,  bulbar  branch  of  same 
the  union  of  these  forms  a  trunk  which 


nerve 


The  glosso-pharyngeal. 


divides  into  two  branches  ;  16,  external  branch  ; 
17,  internal  branch ;  18,  cervical  portion  of  sym- 


pathetic ;  19,  hypoglossal,  cut. 


DIAGRAM   OP   GLOSSO-PHARYNGEAL. 


Fig.  169. 


Fig.  169  :  1,  facial ;  2,  glosso-pharyngeal;  3,  pneumo- 
gastric ;  4,  spinal ;  5,  hypoglossal ;  6,  superior  cervical 
ganglion ;  7,  7,  anterior  branches  of  the  two  first  cervical 
pairs ;  8,  plexus  enveloping  the  internal  carotid  artery ; 
9,  Jacobson's  nerve ;  10,  its  anastomotic  branch  with  the 
carotid  plexus  ;  11,  small  deep  petrosal,  which  passes  into 
the  great  superficial  petrosal;  13,  otic  ganglion ;  14,  anas- 
tomosis of  glosso-pharyngeal  with  lingual  branch  of  the 
facial;  15,  anastomosis  of  glosso-pharyngeal  and  pneumo- 
gastric ;  16,  anastomosis  of  the  pharyngeal  of  the  glosso- 
pharyngeal  with  that  of  the  pneumogastric  and  of  the 
spinal ;  17,  auricular  twig  of  Arnold  ;  18,  application  of 

Diagram  Of  anasto-    the  trunk  of  the  sPinal  to  tlie  superior  ganglion  of  the 
moses.  pneumogastric ;   19,  anastomosis  of  internal  branch  of  the 

spinal  with  the  ganglion  of  the  trunk  of  the  par  vagum  ;  20,  anastomosis 
of  pneumogastric  and  hypoglossal ;  21,  anastomosis  of  hypoglossal  with 
the  loop  formed  by  first  and  second  cervical ;  22,  22,  anastomosis  of  the 
two  first  pairs  with  the  cervical  ganglion ;  23,  pharyngeal  plexus ;  24, 
laryngeal  plexus ;  25,  anastomosis  of  the  external  branch  of  the  spinal 
with  the  anterior  branch  of  the  third  cervical  pair. 


MO  THE   PNEUMOGASTRIC   NERVE. 

OF  THE  TENTH  PAIR,  THE  PAR  VAGUM,  OR  PNEUMOGASTRIC  NERVE. 

The  pneumogastric  nerve  arises  by  six  or  eight  filaments  from  the 
groove  between  the  olivary  and  restiform  bodies  below  the  glosso-pha- 
ryngeal,  and,  like  it,  may  be  traced  to  the  vesicular  material  of  the  floor 
The  tenth  air  °^  tne  fourtn  ventricle.  It  first  presents  a  small  ganglion, 
or  pneumogas-  and  soon  after  a  second,  nearly  an  inch  in  length,  called  the 
plexus  gangliformis.  The  nerve  then  descends  the  neck  in 
the  sheath  of  the  carotid  vessels,  and  in  its  course  differs  on  the  right 
and  left  sides  respectively.  On  the  right  side  it  passes  between  the  sub- 
clavian  artery  and  vein,  descending  toward  the  stomach  and  solar  plexus 
on  the  posterior  portion  of  the  oesophagus  ;  on  the  left  it  enters  the  chest 
nearly  parallel  with  the  left  subclavian,  and  passes  to  the  stomach  and 
solar  plexus  along  the  anterior  portion  of  the  oesophagus. 

The  chief  branches  of  the  pneumogastric  are  the  auricular,  the  pharyn- 
geal,  the  superior  laryngeal,  the  cardiac,  the  inferior  laryngeal  or  recur- 
rent, the  anterior  pulmonary,  the  posterior  pulmonary,  the  cesophageal, 
and  the  gastric. 

The  pneumogastric  presents  several  plexuses  in  its  course,  and,  even 
when  distributed  on  the  stomach,  exhibits  flat,  membraniform  ganglia. 
It  supplies  three  great  classes  of  organs :  1st.  The  digestive,  as  the  pha- 
rynx, oesophagus,  stomach,  liver;  2d.  Respiratory,  as  the  larynx,  trachea, 
lungs ;  3d.  Circulatory,  as  the  heart  and  great  vessels.  It  associates  it- 
self intimately  with  the  sympathetic,  and  aids  it  in  forming  several  great 
plexuses. 

At  its  root  the  pneumogastric  is  sensory,  but  in  its  trunk  it  possesses 
a  double  function,  arising  from  its  intermingling  with  other  nerves,  as  the 
spinal  accessory  and  sympathetic.  Though  the  trunk,  if  irritated,  gives 
rise  to  pain,  we  are  not,  under  ordinary  circumstances,  conscious  of  indi- 
cations, as,  for  example,  in  the  act  of  breathing,  in  which  we  do  not  per- 
ceive the  necessity  of  respiration,  except  the  access  of  the  air  be  too  long 
delayed.  The  pharyngeal  branch  is  the  chief  motor  nerve  of  the  pharynx 
and  palate.  The  superior  laryngeal  is  the  sensory  nerve  of  the  larynx, 
the  inferior  laryngeal  being  the  motor.  Considered  along  with  the  spi- 
nal accessory,  the  pneumogastric  presents  an  analogy  to  a  spinal  nerve ; 
the  accessory  constituting  the  anterior  or  motor  root,  and  the  pneumo- 
gastric, with  its  ganglion,  the  sensory  root. 

The  pneumogastric  nerve  was  formerly  regarded  as  taking  an  influen- 
tial part  in  the  action  of  the  stomach  during  digestion.  The  precise  na- 
ture of  its  agency  in  this,  respect  has  been  already  alluded  to.  In  addi- 
tion, it  may  be  remarked  that  probably  through  this  nerve  is  the  sensa- 
tion of  hunger  conveyed  to  the  mind. 


THE    PNEUMOGASTRIC   NERVE. 


341 


Fig.  170. 


ILLUSTRATION   OF   THE   LEFT  TNEUMOGASTRIC   NERVE. 

Fig.  170 :  1, 1, 1,  the  pneumogastric  nerve ;  2,  anastomosis  of  it  with 
the  hypoglossal ;  3,  anastomosis  of  plexiform  ganglion  with  internal 
branch  of  the  spinal ;  4,  pharyngeal,  passing  in  front  of  the  internal  car- 
otid artery ;  5,  superior  laryngeal,  behind  the  internal  carotid  artery ;  6, 
external  laryngeal ;  7,  laryngeal  plexus,  formed  by  external  laryngeal 
and  great  sympathetic ;  8,  superior  cardiac  ;  9,  middle  cardiac ;  10,  10, 

inferior  laryngeal,  or  recurrent, 
forming  a  curve  round  the  arch 
of  the  aorta ;  11,  pulmonary  gan- 
glion ;  12,  its  anastomosis  with 
the  great  sympathetic  ;  13,  pos- 
terior pulmonary  plexus ;  14, 
cesophageal  plexus;  15,  curves 
formed  around  the  oesophagus 
by  the  right  and  left  pneumo- 
gastrics;  16,  cesophageal  strand 
traversing  the  diaphragm  ;  17, 
plexus  formed  by  the  strand 
upon  the  anterior  face  of  the  car- 
diac end;  18,  branches  for  the 
great  end  of  the  stomach;  19, 
branches  for  the  small  curva- 
ture ;  20,  branches  for  the  ante- 
rior face  of  the  stomach ;  21, 
hepatic  branches  commingling 
with  the  hepatic  plexus  of  the 
great  sympathetic,  and  ramify- 
ing in  the  substance  of  the  liver, 
22,  glosso- pharyngeal.  23,  its 
lingual  branch  ,  24,  pharyngeal 
branch  ;  25,  branch  for  the  sty- 
lo-pharyngeal  muscle;  26,  spi- 
nal ;  27,  internal  branch,  aiding 
to  form  the  pharyngeal  nerve  ; 
28,  external  branch;  29,  twig 

The  left  pneumogastric  nerve.  of  external  branch  anastomos- 

ing  with  the  third  cervical ;  30,  anastomosis  with  trapezian  branch  of 
the  fourth  cervical ;  31,  cervical  portion  of  great  sympathetic ;  32,  32, 
thoracic  portion ;  a,  thyroid  body ;  b,  trachea ;  c,  left  lung,  drawn  to  the 
right ;  d,  liver,  raised ;  e,  oesophagus ;  /,  great  end  of  the  stomach, 
drawn  to  the  left ;  g,  arch  of  the  aorta ;  the  carotid,  and  subclavian  ar- 
teries, cut. 


342 


THE   SPINAL   ACCESSORY   NERVE. 


Fig.  171. 


ILLUSTRATION   OF   PULMONARY   GANGLIA. 


Fig.  172. 


Fig.  171 :  1,1,  pulmonary  ganglia  ;  2,  median  anas- 
tomoses of  these  ganglia  at  the  posterior  face  of  the 
trachea,  and  origin  of  the  bronchi ;  3,  left  laryngeal 
nerve,  aiding  to  form  the  bronchial  plexus  ;  4,  anas- 
tomoses of  the  two  pneumogastrics  on  the  posterior 

Pulmonary  ganglia.        faCC   of  the  O3SOphagUS. 
ILLUSTRATION   OF   INFERIOR   LARYNGEALS,  ANTERIOR   PULMONARY,  AND   CARDIAC    PLEXUS. 

Fig.  172, 1,  1,  pneumogastric ;  2,  2,  superior  laryngeal;  3,  3,  exter- 
nal laryngeal ;  4,  superior  car- 
diac nerve;  5,  5,  middle  cardiac 
nerves  ;  6,  inferior  cardiacs  ;  7, 
cardiac  ganglion  and  plexus ;  8, 8, 
nerves  from  this  plexus  surround- 
ing the  coronary  plexus ;  9,  9,  an- 
terior pulmonary  plexus  ;  10,  10, 
inferior  laryngeal-:  the  left  em- 
bracing the  arch  of  the  aorta,  the 
right  the  subclavian  artery,  both 
go  to  the  posterior  face  of  the 
larynx;  11,  tracheal  branches; 
A,  pulmonary  artery ;  B,  its  left 
branch ;  C,  its  right  branch  ;  D, 
arch  of  the  aorta ;  E,  fibrous  cord 
arising  from  obliteration  of  the 
ductus  arteriosus  ;  F,  left  subclavian ;  G,  G,  left  primitive  carotid ;  H, 
brachio-cephalic  trunk,  cut  to  show  cardiac  nerves ;  I,  vena  cava  supe- 
rior ;  K,  left  coronary  artery  and  vein ;  L,  right  coronary  artery  and 
vein ,  #,  os  hyoides  ;  5,  projecting  portion  of  the  larynx ;  <?,  trachea ;  d, 
thyro-hyoid  muscle  ;  e,  c,  crico-thyroid  ;  /*,  /*,  scalenus  anticus  ;  #,  <?, 
thyroid  body ;  A,  A,  diaphragm ;  ?,  ?",  pericardium,  cut  away. 

OF  THE  ELEVENTH  PAIR,  OR  SPINAL  ACCESSORY  NERVE. 

The  spinal  accessory  arises  by  several  filaments  from  the  side  of  the 
The  eleventh  sPma^  cord,  as  low  as  the  fifth  or  sixth  cervical  nerve.  In 
pair,  or  spinal  its  upward  course  it  communicates  with  the  posterior  roots 
of  the  first  cervical.  It  then  divides  into  two  branches,  the 
smaller  joining  the  pneumogastric,  the  main  trunk  passing  onward,  and 
being  eventually  distributed  to  the  trapezius  muscle,  and  also  furnishing 
supplies  to  the  sterno-mastoid. 

The  spinal  accessory  is  a  motor  nerve,  as  appears  from  the  usual  evi- 


The  inferior  laryngeals. 


THE   HYPOGLOSSAL   AND    PHRENIC   NERVES.  343 

dence  of  irritation,  and  also  from  its  origin  and  distribution.  Its  action 
is  not  essential  in  ordinary  or  involuntary  respiration.  In  voluntary  res- 
piration it  is  brought  into  play. 

OF   THE   TWELFTH   PAIR,  OR   HYPOGLOSSAL  NERVE. 

This  nerve  arises  in  the  groove  between  the  pyramidal  and  olivary 
bodies,  by  8  or  10  filaments,  which  are  collected  into  two  The  twelfth 
bundles.     It  next  passes  forward  and  crosses  inward,  pur-  pair,  or  hypo- 
sues  a  course  which  is  concave  upward,  and  supplies  the  gossal< 
genio-hyoglossus  and  muscles  of  the  tongue  generally,  giving  off  the 
following  branches  in  its  course :  the  descendens  noni,  the  thyro-hyoid, 
and  filaments  connecting  the  gustative  nerve.     It  also  anastomoses  with 
the  pneumogastric,  spinal  accessory,  first  and  second  cervical  nerves,  and 
sympathetic. 

The  hypoglossal  is  the  motor  nerve  of  the  tongue,  irritation  of  it  giv- 
ing rise  to  movements  throughout  that  organ,  the  lingual  branch  of 
the  fifth  being  the  sensory.  The  hypoglossal  causes  the  muscles  of  the 
neck  to  aid  in  the  movements  necessary  for  articulate  speech. 

ILLUSTRATION   OF   THE   HYPOGLOSSAL   NERVE. 

1,  medulla  oblongata;  2,  glosso-pharyngeal ;  3,  pneumo- 
gastric ;  4,  superior  laryngeal ;  5,  spi- 
nal;  6,  first  cervical  pair ;  7,  second 
pair ;  8,  third  pair  ;  9,  fourth  pair ; 
10,  lingual;  11,  origin  of  hypoglos- 
sal ;  12,  anastomosis  of  hypoglossal 
with  first  cervical;  13,  anastomosis 
with  nervous  loop  of  two  first  cervi- 
cals  ;  14,  descending  branch  of  hy- 
poglossal, anastomosing  with,  15,  de- 
scending branches  of  cervical  plexus ; 
16,  twig  of  thyro-hyoid  muscle;  17, 
The  hypogiossai  nerve,  branches  of  hyoglossus  ;  18,  recur- 

rent  branch  of  stylo-glossus  ;  19,  branches  of  genio-hyoid ;  20,  plexiform 
branches  of  hypoglossal ;  21,  anastomotic  branch  with  the  lingual ;  22, 
branch  for  submaxillary  ganglion  ;  A,  vertebral  artery ;  B,  external  car- 
otid ;  C,  lingual ;  D,  temporal ;  E,  internal  maxillary ;  #,  portion  of  the 
condyle  of  the  occipital  bone ;  £,  median  section  of  atlas  ;  c,  styloid  pro- 
cess ;  d,  stylo-glossus  ;  e,  stylo-pharyngeus  ;  /*,  hyoglossus  ;  <?,  genio- 
glossus  ;  A,  pterygoideus  externus  ;  ?,  pterygoideus  internus. 

OF   THE   PHRENIC   NERVE. 

Although  the  phrenic,  or  internal  respiratory  nerve  is  not  strictly  in- 


344 


THE    GEEAT    SYMPATHETIC. 


The  phrenic  eluded  in  the  group  now  under  consideration,  yet,  considering 
nerve.  its  important  connection  with  the  motions  of  respiration,  it  is 

proper  to  describe  and  illustrate  it  here. 

It  arises  from  the  third  and  fourth  cervical  nerves,  aided  by  a  branch 
from  the  fifth,  or  from  the  brachial  plexus,  and  from  the  sympathetic. 
In  its  descent  it  communicates  with  the  lower  cervical  ganglion,  enters 
the  thorax  between  the  subclavian  vein  and  artery,  and,  passing  along 
•the  side  of  the  pericardium,  descends  to  the  diaphragm,  the  right  phrenic 
being  perpendicular,  and  the  left  running  obliquely  round  the  apex  of  the 
heart.  It  is  distributed,  for  the  most  part,  to  both  faces  of  the  diaphragm, 
superior  and  inferior.  It  is  the  motor  nerve  of  the  diaphragm. 


Fig.  174 


The  phrenic  nerve. 


ILLUSTRATION    OF    THE    PHRENIC    NERVE. 

Fig.  174:  1,1,  root  of  the  phrenic 
nerve,  furnished  by  the  fourth  cervi- 
cal ;  2,  2,  roots  from  the  brachial 
plexus  ;  anastomosis  of  this  nerve 
with  branch  of  the  subclavian ;  4, 
anastomosis  with  the  inferior  cer- 
vical ganglion ;  5,  5,  curve  of  the 
hypoglossal,  cut,  sending  a  twig  to 
the  phrenic  nerve  ;  6,  6,  pericardiac 
branches  of  the  phrenic  nerve ;  7, 
7,  branches  to  the  superior  face  of 
the  diaphragm;  8,  8,  branches  to 
the  inferior  face  of  the  diaphragm ; 
9,  anastomoses  .  of  these  branches 
with,  10,  the  solar  plexus  ;  11, 
transverse  communication  of  the 
phrenic  nerves. 


OF  THE  GREAT  SYMPATHETIC  NERVE. 


Under  the  designations  of  sympathetic,  visceral,  toisplanchnic,  gangli- 
Position  and  on*c'  intercosta^  or  nerve  of  organic  life,  passes  a  series  of 
structure  of  the  reddish  or  gray  ganglia,  interconnected  by  nervous  strands, 
sympathetic,  extending  along  each  side  of  the  vertebral  column,  from  the 
head  to  the  coccyx,  communicating  with  all  other  nerves  of  the  body, 
and  distributing  branches  to  the  internal  viscera,  or  organs  of  involunta- 
ry function.  These  ganglia  are  less  numerous  than  the  vertebrae ;  the 
chain  on  each  side  communicates  with  its  colleague  through  plexuses, 
and  the  ganglion  impar  is  the  common  uniting  point  on  the  coccyx  be- 
low. By  some  it  is  supposed  that  the  ganglion  of  Ribes,  and  by  others 
that  the  pituitary  body  has  the  same  function  in  the  cranium  above. 


CONNECTION  OF  SYMPATHETIC  AND   SPINAL. 


345 


What  are  here  spoken  of  as  nervous  strands  are  perhaps  more  correctly 
prolongations  of  the  ganglia  themselves. 

The  origin  of  the  sympathetic  has  been  long  a  subject  of  dispute,  some 
supposing  that  it  is  a  special  system,  of  which  the  ganglia  are  origin  of  the 
so  many  independent  centres,  establishing  incidental  commu-  sympathetic, 
nications  with  the  cerebro-spinal ;  others,  that  its  origin  is  in  the  internal 
viscera,  and  its  termination  in  the  cerebro-spinal  system,  this  opinion  be- 
ing supported  by  the  alleged  facts  that  the  sympathetic,  in  its  develop- 
ment, appears  before  the  other  parts  of  the  nervous  system,  and  simulta- 
neously with  the  splanchnic  organs,  and  that  it  has  been  found  in  mon- 
sters without  a  brain  or  spinal  cord ;  others,  again,  suppose  that  it  orig- 
inates from  the  roots  of  the  cerebro-spinal  system,  and  terminates  in  the 
interior  organs.  Regarding  it  in  this  light,  some  have  imputed  its  origin 
to  all  the  spinal,  and  fifth  and  sixth  cranial  conjointly ;  others  have  lim- 
ited it  to  the  two  latter. 

The  pneumogastric  nerve  aids  it  in  forming  three  of  its  plexuses,  the 
pharyngeal,  cardiac,  and  solar.  In  certain  respects  the  pneu-  Eelations  of 
mogastric  and  sympathetic  seem  to  exhibit  a  reciprocal  de- 
velopment,  in  some  of  the  lower  animals  the  former  pre-  pathetic, 
dominating  over,  and  supplying  the  place  of  the  latter;  and  this  replace- 
ment, it  is  said,  goes  on  in  the  descending  series  until,  in  the  cephalopo- 
dous  mollusks,  the  sympathetic  has  disappeared,  and  the  pneumogastric 
takes  its  place. 

Fig.  175  illustrates  the  relation 
of  the  sympathetic  and  spinal  nerves : 
c,  c,  anterior  fissure  of  the  spinal 
cord ;  «,  anterior  root  of  a  dorsal 
spinal  nerve ;  p,  posterior  root,  with 
its  ganglion ;  #',  anterior  branch ;  p'9 
posterior  branch ;  s,  sympathetic ;  <?, 
its  double  junction  with  the  anterior 
branch  of  the  spinal  nerve  by  a  white 
and  a  gray  filament. 

The  sympathetic  chain  therefore 
establishes  connections  Connection  of 
with  the  cerebro-spinal  SfgSfe 
system.  Each  spinal  tem. 
nerve  is  brought  into  relation  with 
it  through  two  strands,  a  tubular  or 
white,  and  a  gelatinous  or  gray. 
The  tubular  or  white  strand  may  be 
regarded  as  actually  arising  from  the 
spinal  cord,  and  consisting  of  motor 

Relation  of  the  sympathetic  and  spinal.  an(J  SenSOry  filaments.       It  makes  its 


Fiy.  1T5. 


346  THE   GKEAT   SYMPATHETIC. 

way  to  the  ganglion  of  the  sympathetic,  passes  over  and  through  it,  its 
fibres  conjoining  themselves  with  gray  ones,  which  they  have  gathered  in 
the  ganglion.  The  gray  or  gelatinous  root  is  to  "be  viewed  as  having  its 
origin  in  the  ganglion  of  the  sympathetic,  and  ^sending  its  fibres  chiefly 
to  the  ganglion  on  the  posterior  root  of  the  spinal  nerve,  but  few  of  them 
doubtfully  communicating  with  the  anterior  root.  The  fibres  which  seem 
to  enter  the  cord  are  probably  for  the  supply  of  blood-vessels.  Each  of 
these  sympathetic  ganglia  is,  therefore,  a  nervous  centre,  sending  forth 
strands  in  three  directions :  1st.  To  join  the  spinal  fibres  in  their  distri- 
bution ;  2d.  To  the  spinal  cord  itself,  or  chiefly  to  the  ganglia  on  the  pos- 
terior roots  of  its  nerves ;  3d.  To  the  next  sympathetic  ganglion  above. 
Sympathetic  In  the  various  plexuses  of  the  sympathetic,  vesicles  are  found, 
plexuses.  from  whicn  g^y  fibres  seem  to  originate.  The  branches  which 
supply  the  viscera  constantly  form  plexuses  ;  the  arteries  are  surrounded 
with  such  a  net-work.  The  splanchnic  ganglia,  with  their  interconnect- 
ing strands,  and  supplies  from  the  cerebro-spinal,  give  rise  to  four  great 
plexuses:  the  pharyngeal,  the  cardiac,  the  solar,  and  the  hypogastric. 
The  first  and  last  of  these  are  in  symmetrical  pairs ;  the  other  two  are 
single,  and  placed  on  the  median  line. 

From  its  construction  the  sympathetic  can  not  be  regarded  as  an  iso- 
Ph -sical  effects  ^ate^  or  self-acting  system,  since  all  its  branches  contain 
of  sympathetic  fibres  derived  from  the  cerebro-spinal.  In  function  it  must 
therefore  be  adjuvant  to  that  system,  and  it  must  be  admit- 
ted that  the  motor  and  sensory  qualities  of  the  included  spinal  fibres,  ac- 
cording as  they  have  been  derived  from  the  anterior  or  posterior  columns 
of  the  cord,  are  continued  in  their  association  with  the  sympathetic. 
Hence,  in  so  far  as  being  a  compound  nerve,  it  possesses  both  those  func- 
tions, and  this  conclusion  is  corroborated  by  such  facts  as  those  of  the 
distribution  of  the  sympathetic  both  to  muscular  portions,  as  to  the  heart, 
and  also  to  sensitive  ones  ;  by  the  circumstance  that  the  intestinal  canal 
from  the  stomach  to  the  end  of  the  colon  receives  its  nervous  supply 
from  this  source  alone.  Experiments  on  the  sympathetic  ganglia  estab- 
lish a  similar  conclusion,  irritation  of  the  cceliac  ganglion,  for  instance, 
giving  rise  to  increased  peristaltic  motions,  and  pathological  observations 
furnishing  like  evidence  as  regards  the  sensory  function.  Compared 
with  other  nerve  trunks,  the  sympathetic  is  much  less  active  in  these  re- 
spects, a  high  irritation  of  the  parts  supplied  by  it  often  being  required 
to  cause  pain,  and,  in  like  manner,  its  motor  fibres  are  little  under  the  in- 
fluence of  the  will. 

The  sympathetic  transmits  sensations  so  tardily  that  it  has  been  sup- 
posed that  one  office  of  its  ganglia  is  for  the  purpose  of  cutting  off  such 
impressions ;  and,  in  like  manner,  when  motor  fibres  of  the  cerebro-spi- 
nal system  pass  through  its  ganglia,  their  conducting  power  appears  to 


THE   GREAT   SYMPATHETIC.  347 

be  impaired.  There  does  not  seem  to  be  any  decisive  proof  that  any  of 
the  fibres  of  the  sympathetic,  properly  speaking,  are  motor  or  sensory,  or 
that  its  ganglia  produce  reflex  action,  the  agency  which  it  exerts  in  these 
respects  on  the  muscular  structure  of  the  heart,  blood-vessels,  digestive 
or  urinary  organs,  being  due  to  the  associated  cerebro-spinal  fibres. 

In  this  manner,  by  its  distribution  to  the  arteries,  the  sympathetic,  as 
a  compound  nerve,  exerts  a  power  over  the  passage  of  the  blood  through 
them  by  influencing  their  contractility,  and  thereby  their  diameter.  In 
virtue  of  this,  it  therefore  affects  the  rapidity  of  secretion,  and  also  regu- 
lates the  rate  of  nutrition.  The  entire  digestive  tract,  with  its  dependen- 
cies are  thus  brought  under  its  influence,  the  salivary  glands,  pharynx, 
oesophagus,  stomach,  intestine,  nasal,  bronchial,  and  pulmonary  sur- 
faces, etc. 

The  view  of  the  function  of  ganglia  presented  on  preceding  pages  is 
strongly  supported  by  the  mechanism  and  phenomena  of  the  Itg  an  Ha  are 
sympathetic  nerve.     Its  ganglia  permit  the  influence  passing  reservoirs  of 
along  the  nervous  cords  to  escape  therefrom  into  new  chan-    ( 
nels,  and  also  retain  and  store  up  nervous  power.     They  become,  there- 
fore, magazines  of  force,  and  are  hence  capable  of  sustaining  rhythmic 
movements.     Even  after  organs  have  been  exsected,  they  will  still  exhib- 
it, under  the  influence  of  these  ganglia,  their  accustomed  motion,  as  is  the 
case  with  the  heart,  which,  in  some  of  the  cold-blooded  animals,  will  con- 
tinue its  contractions  for  many  hours  after  it  has  been  cut  out  of  the  body. 

I  therefore  regard  the  sympathetic  system  as  having  for  one  of  it& 
main  functions  the  equalization  or  balancing  of  the  nervous  Conclusion 
force,  storing  up  all  transient  excesses  of  it,  and  furnishing  f^Sn^ftiL 
all  transient  deficiencies.  As  in  a  mechanical  contrivance,  sympathetic. 
in  which  the  prime  mover  works  in  an  irregular  way,  the  fly-wheel  har- 
monizes all  such  variations,  storing  up  or  supplying  power  as  the  cir- 
cumstances may  require,  so  does  this  complicated  apparatus  act  in  the 
mechanism  of  innervation.  And  it  is  worthy  of  remark,  that  some  such 
arrangement  would  seem  to  be  necessary,  since  the  organs  of  digestion,  to 
which  the  sympathetic  is  so  largely  directed,  are  periodically  in  activity 
and  periodically  quiescent. 

It  is  to  be  greatly  regretted  that  the  term  sympathetic  has  been  ap- 
plied to  this  important  nerve,  since  that  term,  as  defining  function,  has 
led  to  the  promulgation  of  theoretical  views  which  have  exerted  an  influ- 
ence to  the  disadvantage  of  the  progress  of  physiology — views  which  will 
not  bear  the  test  of  anatomical  criticism,  and  which  are  therefore  incor- 
rect. It  is  always  much  better  to  give  designations  in  allusion  to  struc- 
ture or  position  than  to  function,  especially  where  the  function  is  doubt- 
ful. For  this  reason,  the  title  of  intercostal  is  much  preferable  to  that 
of  nerve  of  organic  life,  and  trisplanchnic  better  than  sympathetic — an 


348 


THE    GKEAT    SYMPATHETIC. 


imposing  but  mysterious  epithet,  which  has  been  a  source  of  injury  to 
the  science,  and  which  it  would  be  well  even  now  to  replace  by  such  a 
term  as  vincular  or  moniliform  nerve,  or  some  title  of  equivalent  import. 


ILLUSTRATION   OF   THE    GREAT    SYMPATHETIC. 

Fig-m'  Fig.  176:   1,  globe  of  the  eye, 

dissected  so  as  to  show  the  ciliary 
nerves ;  2,  branch  of  the  inferior  ob- 
lique and  the  motor  root  of  the  oph- 
thalmic ganglion  ;  3, 3, 3,  the  three 
branches  of  the  trifacial,  in  connec- 
tion with  most  of  the  cranial  gan- 
glia, that  is,  with,  4,  ophthalmic  gan- 
glion, 5,  spheno-palatine,  6,  otic,  7, 
submaxillary,  and,  8,  sublingual ; 
9,  external  motor  oculi;  10,  facial 
and  its  anastomoses  with  the  sphe- 
no-palatine and  otic  ganglia  ;  11, 
glosso  -  pharyngeal ;  12,  12,  right 
pneumogastric  ;  13,  left  pneumo- 
gastric;  14,  spinal;  15,  hypoglos- 
sal;  16,  16,  cervical  plexus;  17, 
brachial  plexus  ;  18, 18,  intercostal 
nerves ;  19,  19,  lumbar  plexus  ; 
20,  sacral  plexus  ;  21,  superior  cer- 
vical ganglion,  furnishing  two  caro- 
tid branches,  forming  the  carotid 
plexus  around  the  artery  of  that 
name,  and  from  which  arise  the 
anastomoses  with,  22,  nerve  of  Ja- 
cobson,  23,  carotid  branch  of  vid- 
ian  nerve,  24,  external  motor  oc- 
uli, 25,  ophthalmic  ganglion  ;  26, 
twig  for  the  pituitary  gland;  27, 
anastomosis  of  superior  cervical 
ganglion  with  the  first  cervical 
pairs ;  28,  carotid  and"  pharyngeal 
branches ;  29,  pharyngeal  and  in- 
tercarotid  plexus  ;  30,  laryngeal 
branch,  anastomosed  with  the  external  laryngeal  of  the  pneumogastric ; 
31,  superior  cardiac  nerve  ;  32,  strands  of  junction  of  the  superior  cervi- 
cal ganglion  with,  33,  middle  cervical  ganglion  :  among  the  internal 
branches  of  the  latter  are,  34,  the  anastomotic  with,  35,  the  recurrent 


The  great  sympathetic  nerve. 


THE  ABDOMINAL  PLEXUSES. 


349 


nerve,  36,  middle  cardiac  nerve ;  37,  strand  of  junction  of  middle  cervical 
ganglion  with,  38,  inferior  cervical  ganglion ;  40,  twigs  furnished  by  in- 
ferior cervical  ganglion  around  the  subclavian  and  vertebral  arteries  ;  41, 
anastomotic  branch  with  the  first  intercostal  nerve ;  42,  cardiac  plexus 
and  ganglion ;  43,  44,  secondary  plexuses  of  right  and  left  coronary  ar- 
teries ;  from  45  to  46,  thoracic  ganglionary  chain ;  47,  the  great  splanch- 
nic traversing  the  diaphragm,  and  going  to,  48,  semilunar  ganglion  ;  49, 
little  splanchnic ;  50,  solar  plexus,  receiving,  51,  anastomosis  of  pneu- 
mogastric,  52,  phrenic  nerve;  53,  gastric  coronary;  54,  hepatic;  55,  sple- 
nic ;  56,  superior  mesenteric,  enveloping  the  arteries  of  those  names ;  57, 
renal  plexus ;  from  58  to  58,  lumbar  ganglionic  chain;  59,  lumbo-aortic 
plexus,  presenting  two  enlargements,  one,  60,  above,  the  other,  61,  below 
the  bifurcation  of  the  aorta;  62,  spermatic  plexus ;  63,  inferior  mesenteric; 
64,  hypogastric  plexus  ;  65  to  65,  sacral  ganglionic  chain ;  66,  terminal 
coccygeal  ganglion ;  A,  heart,  slightly  turned  aside  to  show  the  cardiac 
plexus  ;  B,  arch  of  the  aorta,  also  drawn  aside  by  hook ;  C,  innominata  ; 
D,  subclavian,  cut,  to  show  inferior  cervical  ganglion ;  E,  inferior  thy> 
roid;  F,  portion  of  external  carotid;  G,  internal  carotid;  H,  thoracic 
aorta ;  I,  abdominal  aorta ;  J,  primitive  iliac ;  K,  intercostals  ;  L,  pul- 
monary artery,  of  which  the  right  branch  is  cut ;  M,  superior  vena  cava, 
cut  at  its  origin ;  N,  vena  cava  inferior ;  O,  pulmonary  veins ;  #,  lach- 
rymal gland ;  &,  sublingual  gland ;  c,  submaxillary  gland ;  d,  thyroid 
body ;  e,  trachea  ;  f,  oesophagus,  going  to,  g,  the  stomach ;  A,  several  in- 
testinal loops  with  superior  mesenteric  plexus ;  i,  transverse  colon ;  j9 
sigmoid  flexure  ;  &,  rectum  ;  Z,  bladder ;  m,  ureter ;  ft,  prostate ;  o,  ve- 
Fi9-  ™-  sicula  seminalis ;  p,  vas  deferens ;  £,  sperm- 

atic cord;  r,  r,  diaphragm. 


THE  ABDOMINAL  PLEXUSES. 


The  abdominal  plexuses. 


Fig.  177:  1,  1, 1,  1,  portion  of  the  right 
and  left  ganglionic  chain ;  2,  coccygeal  gan- 
glion ;  3,  median  anastomoses  of  the  two 
sacral  cords ;  4,  4,  great  splanchnic,  right 
and  left,  traversing  the  diaphragm,  and  go- 
ing to,  5,  5,  semilunar  ganglia ;  6,  solar 
plexus  ;  7,  splenic  plexus ;  8,  hepatic  plex- 
us ;  9,  coronary  plexus  of  stomach ;  10, 
anastomoses  of  the  two  pneumogastrics, 
right  and  left,  with  solar  plexus  and  gastric 
coronary;  11,  diaphragmatic  plexus  and  su- 
perior capsular;  12,  anastomoses  of  these 
two  plexuses  with  the  phrenic  nerve ;  13, 
middle  capsular  plexus  ;  14,  inferior  capsu- 


350 


THE   SOLAR   PLEXUS. 


lar  plexus,  coming  from,  15,  renal  plexus ;  16,  16,  lesser  splanchnics, 
traversing  the  diaphragm;  17,  superior  mesenteric  plexus;  18,  sperm- 
atic plexus,  arising  from  three  sources,  the  renal,  lumbo-aortic,  and  hypo- 
gastric;  from  19  to  19,  lumbo-aortic  plexus;  20,  20,  its  bifurcations; 
21,  inferior  mesenteric  plexus ;  22,  22,  its  anastomoses  with,  23,  23, 
hypogastric  plexus  on  each  side ;  24,  24,  sacral  plexus  ;  «,  diaphragm, 
cut ;  £,  portion  of  stomach  and  oesophagus  ;  c,  spleen ;  d,  kidney  and  its 
supra-renal  capsule  ;  e,  testicle ;  /*,  ureter,  cut ;  A,  A,  aorta. 


THE    SOLAR   PLEXUS. 


Fig.  178:  1,  solar  plexus,  furnishing,  2,  hepatic  plexus;  3,  gastric 
coronary  plexus,  and,  4,  splenic  plexus  ;  5,  anastomoses  of  right  and  left 
pneumogastric  with  the  solar  plexus  and  gastric  coronary ;  6,  branches 
of  pneumogastric  going  to  the  liver ;  7,  plexus  of  biliary  ducts;  8,  origin 
of  superior  mesenteric  plexus ;  9,  renal  plexus ;  10,  capsular  plexus ; 
11,  11,  spermatic  plexus;  12,  commencement  of  lumbo-aortic  plexus; 
13,  portion  of  inferior  mesenteric  plexus ;  a,  the  liver,  raised ;  £,  the  stom- 
ach, cut  at  its  great  end ;  £,  the  spleen ;  d,  the  kidney ;  e,  kidney,  cut ; 
f,  supra-renal  capsule  ;  <7,  <?,  ureters  ;  .  Fig.  ITO. 

\  duodenum ;  i,  i,  pancreas. 


11  a  »     tt 

The  solar  plexus. 


The  mesenteric  plexuses. 


SUPERIOR  MESENTERIC   AND    INFERIOR   MESENTERIC   PLEXUS. 

Fig.  179:  1,  superior  mesenteric  plexus,  surrounding  the  divisions  of 
the  artery  of  the  same  name,  and  offering  many  flat  ganglia ;  2,  portion 
of  inferior  mesenteric  plexus ;  #,  ccecum  and  appendix  vermiformis ;  b,  b, 
transverse  colon ;  <?,  portion  of  small  intestine. 


THE   VOICE.  351 


CHAPTER  XVIII. 

OF  THE  VOICE. 

Origin  of  the  Voice. —  Comparative  Physiology  of  Noise,  Song,  Voice. — Distinction  between  Song 
and  Speech.— The  Larynx,  and  its  Action  in  Singing. — Mutter's  Explanation  of  the  Action  of 
the  Vocal  Organs. — Speaking  Animals  and  Machines. 

Nature  of  Words  and  their  constituent  Sounds. —  Vowels  and  Consonants. —  Whispering. —  Use 
of  the  Voice  of  Animals. 

Of  Languages:  their  Duration,  Character,  History. — Registry  of  Sounds  by  Writing  and  Print- 
ing.— Musical  Signs. — Alphabetic  Writing. 

FOR  the  production  of  the  sounds  necessary  for  intercommunication 
among  the  higher  animals,  and  particularly  for  the  speech  of  Voice  arises 
man,  it  might  be  supposed  that  some  complicated  and  elab-  p^ults^of 
orate  contrivance  must  needs  be  resorted  to.  This  object  is,  respiration, 
however,  accomplished  by  merely  employing,  on  its  escape  from  the  sys- 
tem, the  wasted  product  of  respiration,  the  breath,  which,  as  it  issues  out- 
ward through  the  respiratory  passages,  sets  in  motion  a  simple  mechan- 
ism, and  thereby  originates  all  the  exquisite  modulations  of  song,  and 
all  the  impressive  utterances  of  speech.  Is  it  not  to  be  admired  that 
thus,  out  of  dead  and  dismissed  matter,  results  of  so  high  an  order,  ma- 
terially and  mentally,  are  obtained? 

What  might  be  termed  the  comparative  physiology  of  the  voice  is  very 
simple.  It  appears*  first  in  invertebrate  animals  as  a  mo-  Com  arative 
notonous  noise  or  cry,  which  gradually,  in  higher  tribes,  be-  physiology  of 
comes  more  varied  in  loudness  and  note.  It  is  worthy  of  ' 
remark  that,  in  the  different  stages  of  his  existence  man  himself  furnishes 
an  illustration  of  this  course.  Voiceless  before  birth,  with  a  piteous  or 
monotonous  cry  in  early  infancy,  articulate  speech  and  song  are  the  re- 
sult of  education,  and  through  these  the  power  is  eventually  gained  of 
expressing  the  most  refined  emotions  and  the  most  elevated  ideas.  The 
solitary  bell-like  sound  which  the  nudibranchiate  gasteropods  emit,  thus 
produces,  by  its  successive  improvements,  a  wonderful  result  at  last. 

Among  insects  the  modes  of  producing  sounds  are  very  various,  some 
effecting  it  by  percussion,  some  by  the  friction  of  horny  or-  Production  of 
gans.      In  others,  the   extremity  of  the  trachea,  through  rudimentary 
which  the  air  escapes,  is  accommodated  with  vibrating  mem-  sounds- 
branes.     According  to  Burmeister,  the  contractions  of  the  muscles  of  the 
wings,  which  are  brought  vigorously  into  action  during  flying,  occasion 


352  RUDIMENTARY  SOUNDS. 

an  alternate  pressure  and  relaxation 
upon  the  tracheal  tubes.  The  air, 
thus  passing  in  and  out,  throws  into 
vibration  the  valves  of  the  spiracle, 
which,  as  seen  in  Fig.  180,  are  sus- 
pended upon  a  dozen  or  more  flexible 
supports  ;  but  their  free  edges,  ap- 
proaching within  a  certain  distance  of 
each  other,  are  thrown  into  quick  vi- 
bration by  the  passing  current,  in  the 
same  manner  as  is  the  vibrating  spring 
of  the  accordeon.  These  vibrating 
plates  of  insects  are  the  rudiments  of 

Spiracle  of  insect  what  ^  become  fa  perfect  ^£  ap_ 

paratus  in  man.  Again,  in  others,  the  swiftly-recurring  beating  of  the 
wings  produces  a  sound,  as,  for  example,  in  the  musquito.  Among  ver- 
tebrated  animals,  those  which  breathe  the  air  are  vocal,  nearly  all  fishes 
Sounds  of  rep-  being  mute.  From  fishes,  as  we  pass  upward,  the  sound 
tiles  and  birds.  an(j  t ne  instrument  which  makes  it  increase  together  in  com- 
plexity. Through  a  simple  chink,  the  air  expelled  from  the  respiratory 
sacs  of  snakes,  by  the  contraction  of  their  abdominal  muscles,  issues 
forth  as  a  mere  hiss,  the  sound  being  increased  in  the  frog  by  the  devel- 
opment of  resonant  cavities.  From  these  simple  noises  we  are  conduct- 
.ed  to  the  musical  notes  of  birds,  some  of  which  are  of  exquisite  purity 
and  sweetness.  In  these,  the  vocal  glottis  is  situated  at  the  bifurcation 
of  the  trachea,  another  glottis  being  above  for  the  final  es- 
cape of  the  air.  These  vertebrated  animals  first  introduce 
us  to  the  mechanism  for  articulate  speech,  the  rav&n  and  parrot  being 
able  to  pronounce  words  with  distinctness.  The  articulation  is  effected, 
as  in  man,  by  the  motions  of  the  tongue  and  other  portions  of  the  mouth. 
For  the  further  consideration  of  this  subject,  it  is  necessary  to  under- 
Distinction  be-  s^an(^  tnat  there  ig  a  distinction  between  song  and  speech, 
tween  song  and  Song  is  produced  by  the  glottis,  speech  by  the  mouth;  or, 
speech.  perhaps,  a  more  correct  statement  would  be,  that  the  larynx 

is  the  organ  of  song,  the  mouth  of  that  form  of  speech  which  we  call 
whispering,  and  for  which  nothing  is  required  but  a  stream  of  air  issuing 
from  the  fauces,  the  tongue  and  other  organs  giving  it  articulation ;  but 
for  audible  speech,  a  noise  is  created  in  the  larynx,  and  modified  by  ar- 
ticulation in  the  mouth. 

The  double  larynx  of  birds  is  replaced  by  a  single  larynx  in  man, 
which  serves  at  the  same  time  for  the  entrance  and  exit  of  air,  and  like- 
wise for  vocalization.  Those  birds  in  which  the  lower  larynx  is  absent 
are  voiceless.  A  general  idea  of  the  construction  of  the  organ  of  voice 


ACTION  OF  THE  VOCAL  COEDS.  353 

in  man  may  be  gathered  by  supposing  it  to  be  composed  of  three  por- 
tions, the  trachea,  the  larynx,  and  the  mouth.  The  trachea  Description  of 
is  the  tube  by  which  air  is  brought  from  the  lungs  and  de-  the  larJnx- 
livered  into  the  larynx,  which  is  a  superposed  structure,  arranged  upon 
the  cricoid  cartilage,  on  which  is  articulated  the  thyroid  cartilage  by  its 
lower  horns,  around  which  a  certain  degree  of  rotation  can  be  accomplish- 
ed, so  that  the  front  of  the  thyroid  may  be  elevated  or  depressed  with  a 
kind  of  bowing  motion.  Posteriorly,  on  the  cricoid  cartilage  are  placed 
the  arytenoid  cartilages,  which  can  be  approached  or  separated  from  each 
other,  and  from  their  summits  pass  to  the  front  of  the  thyroid  cartilage 
the  inferior  laryngeal  ligaments  or  vocal  cords.  These  constitute  the 
essential  organ  of  sound.  The  thyroid  cartilage,  by  its  motions,  can  de- 
termine the  strain  put  upon  them,  and  the  arytenoids  can  either  bring 
them  into  parallelism,  or  place  them  at  an  acute  angle.  The  chink  or  fis- 
sure between  them  is  the  rima  glottidis  :  its  figure  and  width  vary  with 
the  recession  or  approximation  of  the  vocal  cords,  which,  as  the  air  passes 
by  them,  are  thrown  into  vibration  in  the  same  manner  as  the  reed  in  mu- 
sical instruments.  The  epiglottis  cartilage,  which  is  above,  guards  the 
passage,  and  may  also  be  supposed,  by  its  descent,  to  deaden  the  sounds. 

The  slowness  or  rapidity  of  the  vibration  is  dependent  on  the  stretch 
of  the  vocal  cords.  The  manner  in  which  various  degrees  Regulation  of 
of  tension  can  be  given  to  the  cords  is  readily  understood  by  thevocai  cords, 
considering  their  attachments.  In  front,  as  we  have  said,  they  are  fast- 
ened to  the  thyroid  cartilage,  posteriorly  to  the  arytenoids.  When  the 
thyroid  cartilage  executes  a  bowing  motion  forward,  the  vocal  cords  are 
put  upon  the  stretch,  and  similar  variations  of  their  tension  and  also  of 
their  position  can  be  given  by  the  movements  of  the  arytenoid  cartilages 
behind.  When  the  air  is  moving  in  and  out  without  giving  rise  to  any 
sound,  the  chink  of  the  glottis  is  angular,  its  point  being  forward,  and 
from  that  the  cords  diverge  posteriorly.  For  the  production  of  sound, 
the  cords  must  be  brought  parallel,  or  even  inclining  toward  each  other. 
If  they  incline  away  from  each  other,  no  sound  will  be  produced.  The 
pitch  of  the  note  will  be  determined  by  the  stretch  of  the  cords,  and  this, 
in  its  turn,  will  be  determined  by  the  contraction  of  the  vocal  muscles. 
The  crico-thyroid  and  sterno-thyroid  bow  the  front  of  the  thyroid  cartil- 
age down,  the  thyro-arytenoid  and  thyro-hyoid  carry  it  back ;  the  for- 
mer therefore  stretch  the  cords,  and  the  latter  relax  them.  The  opening 
of  the  glottis  is  likewise  determined  by  other  muscles,  the  posterior  cri- 
co-arytenoid  dilating  it,  and  the  lateral  crico-arytenoid  and  the  transverse 
arytenoid  closing  it. 

Fig.  181,  p.  354,  is  the  larynx,  seen  in  profile :  <z,  a,  half  of  the  hyoid 
bone ;  b,  thyroid  cartilage,  cut ;  c,  thyro-hyoid  membrane ;  <#,  cricoid 
cartilage ;  e,  trachea ;  f,  oesophagus  ;  g,  epiglottis ;  A,  great  horn  of  the 

Z 


354 


ACTION   OF   THE   VOCAL   ORGANS. 


Fig.  181. 


of  larynx. 


Posterior  view  of 
larynx. 


thyroid  cartilage,  united  to,  t,  the  great  horn  of  the  os  hy- 
oides  by,  &,  the  lateral  thyro-hyoid  ligament ;  Z,  thyro-hyoid 
membrane,  traversed  by  the  superior  laryngeal  nerve ;  m, 
posterior  crico-arytenoid  muscle ;  ft,  lateral  crico-arytenoid ; 
1,  inferior  laryngeal  nerve;  2,  posterior  crico-arytenoid 
twigs  ;  3,  lateral  crico-arytenoid  twigs ;  4,  thyro-arytenoid 
twigs  ;  5,  arytenoid  twig. 

Fig.  182  is  the  posterior  view  of  the  lar- 
ynx :  a,  base  of  the  tongue ;  £,  posterior  bor- 
der of  the  thyroid  cartilage  ;  c,  <?,  thyroid  body ;  d,  pos- 
terior crico-arytenoid  muscle ;  0,  arytenoid  muscle ;  1,1, 
superior  laryngeal,  traversing  the  superior  thyro-hyoid 
membrane,  and  giving  off  lingual  and  epiglottic  branches, 
and  others  to  the  mucous  membrane  covering  the  poste- 
rior face  of  the  larynx ;  2,  twig  for  the  arytenoid  muscle ; 
3,  anastomotic  of  Galien  ;  4,  inferior  laryngeal ;  5,  tra- 
cheal  branches ;  6,  twig  for  the  posterior  crico-arytenoid 
muscle ;  7,  twig  for  the  arytenoid  muscle ;  8,  branch  for  the  lateral  crico- 
arytenoid  and  posterior  crico-arytenoid  muscles. 

The  researches  of  Miiller  furnish  the  best  account  we  possess  of  the 
Midler's  ex-  action  of  the  vocal  organs.  He  has  shown  that  the  larynx 
the  action  of  the  *s  essentially  a  reed  instrument  with  a  double  membranous 
vocal  organs,  tongue.  That  the  rima  glottidis  is  the  seat  of  the  origin  of 
the  sound  is  proved  by  the  fact  that  when  an  aperture  exists  in  the  tra- 
chea below  the  glottis  the  voice  disappears,  but  if  above  the  glottis  there 
is  no  effect.  Magendie  records  the  case  of  a  man  who  had  a  fistulous 
opening  in  his  trachea,  and  who  could  not  speak  unless  he  closed  it  or 
wore  a  tight  cravat.  Moreover,  the  human  or  animal  larynx  can  be  made 
to  produce  its  characteristic  sounds  with  more  or  less  distinctness,  after  it 
has  been  removed  from  the  body,  by  directing  a  current  of  air  through 
the  trachea.  Cases  have  occurred  which  have  afforded  the  opportunity 
of  observing  the  condition  of  the  glottis  while  emitting  sounds.  The 
vocal  cords  are  brought  into  parallelism  with  one  another,  and  separated 
by  an  interval  of  scarcely  more  than  from  the  y^  to  the  y|^  of  an  inch  ; 
but  when  the  air  is  moving  in  and  out  silently,  the  fissure  assumes  a  di- 
vergent or  triangular  form. 

Professor  Miiller  gives  the  following  account  of  the  mode  of  produc- 
tion of  the  notes  of  the  natural  voice.  "  The  vocal  ligaments  vibrate  in 
their  entire  length,  and  with  them  the  surrounding  membranes  and  the 
thyro-arytenoid  muscles.  For  the  deepest  notes,  the  vocal  ligaments  are 
much  relaxed  by  the  approximation  of  the  thyroid  to  the  arytenoid  car- 
tilages. The  lips  of  the  glottis  are,  in  this  state  of  the  larynx,  not  only 
quite  devoid  of  tension  j  they  are,  when  at  rest,  even  wrinkled  and  pli- 


OF  SINGING.  355 

cated,  "but  they  become  stretched  "by  the  current  of  air,  and  thus  acquire 
the  degree  of  tension  necessary  for  vibration.  From  the  deepest  note 
thus  produced,  the  vocal  sounds  may  be  raised  about  an  octave  by  al- 
lowing the  vocal  cords  to  have  a  slight  degree  of  tension,  which  the  elas- 
tic crico-thyroid  ligament  can  give  them  by  drawing  the  thyroid  cartilage 
toward  the  cricoid.  The  medium  state,  in  which  the  cords  are  neither 
relaxed  and  wrinkled  nor  stretched,  is  the  condition  for  the  middle  notes 
of  the  natural  register,  those  which  are  most  easily  produced.  The  or- 
dinary tones  of  the  voice  in  speaking  are  intermediate  between  these  and 
the  deep  bass  notes.  The  higher  notes  are  produced  and  the  correspond- 
ing falsetto  notes  avoided  by  the  lateral  compression  of  the  vocal  cords, 
and  by  the  narrowing  of  the  space  beneath  them  by  means  of  the  thyro- 
arytenoid  muscles,  and  farther  by  increasing  the  force  of  the  current  of 
air ;  the  muscular  tension  given  to  the  lips  of  the  glottis  by  the  muscles 
above  mentioned  must  also  be  taken  into  account,  as  contributing  to  the 
production  of  the  notes  of  the  natural  register." 

An  artificial  larynx,  constructed  in  such  a  way  as  to  represent  more 
or  less  perfectly  the  preceding  conditions,  will  give  rise  to  Artificial  la- 
sounds  analogous  to  those  of  the  human  larynx.      Such  have  rynx- 
been  made  of  leather,  and,  better  still,  of  caoutchouc. 

The  narrower  the  glottis  is  made,  and  the  more  tightly  the  cords  are 
strained,  the  more  rapidly  they  will  vibrate,  and  the  higher  will  be  the 
musical  note  emitted.  In  an  individual  the  range  of  the  Relations  of  the 
voice  is  rarely  three  octaves,  but  the  male  and  female  voice,  larynx  in  sing- 
taken  together,  may  be  considered  as  reaching  to  four.  Gen-  mg' 
erally,  the  lowest  female  note  is  about  an  octave  higher  than  the  lowest 
male,  a  similar  remark  applying  to  their  highest  notes  respectively. 
They  differ  also  intrinsically  from  each  other,  just  as  different  wind  in- 
struments sounding  the  same  note  give  it  of  a  different  quality.  More- 
over, in  each  sex  there  arc  different  voices  :  in  the  male,  the  base  and  the 
tenor ;  in  the  female,  the  contralto  and  soprano.  The  base  usually  reach- 
es lower  notes  than  the  tenor,  and  the  tenor  higher  than  the  base ;  the 
contralto  reaches  usually  lower  notes  than  the  soprano,  and  the  soprano 
higher  ones  than  the  contralto,  though  these  distinctions  are  by  no  means 
uniform.  There  are,  again,  intermediate  complications :  thus  the  bary- 
tone intervenes  between  the  base  and  the  tenor,  and  the  mezzo  soprano 
between  the  contralto  and  soprano.  The  chief  reason  for  the  difference 
between  the  voice  in  the  sexes  is  in  the  difference  of  the  length  of  their 
vocal  cords,  which  are  in  men  and  women*  respectively  in  the  proportion 
of  three  to  two ;  but  besides  this,  those  personal  peculiarities  which  we 
so  readily  recognize  in  the  voices  of  individuals  are  due  to  differences  in 
the  structure  of  the  tissues  forming  the  vocal  mechanism,  or  peculiarities 
in  the  size  and  condition  of  the  resonant  cavities.  Frequently  the  same 


356  NATURE  OF  VOCAL  SOUNDS. 

individual  is  capable  of  singing  in  two  different  voices,  known  as  chest 
notes  and  falsetto  notes.  The  chest  notes  are  produced  by  the  ordinary 
mode  of  vibration ;  the  falsetto  notes,  which  are  purer  or  more  fluty,  are 
considered  to  be  probably  due  to  vibrations  of  the  harmonic  subdivisions 
of  the  column  of  air  in  the  trachea,  or  to  vibrations  of  the  inner  borders 
of  the  vocal  cords. 

While  thus  song  is  laryngeal,  speech,  which  is  a  modification  thereof, 
Speaking  ani-  *s  ora*'  or  Produced  ^7  tne  mouth.  Man  is  not  alone  endow- 
mais  and  ma-  ed  with  the  faculty  of  uttering  articulate  sounds :  there  are 
several  other  animals  which,  by  education,  may  be  taught  to 
express  them.  Ingenious  mechanics  have  also  repeatedly  invented  in- 
struments, the  construction  of  which,  being  upon  the  same  principle  as 
that  of  the  vocal  organs,  has  combined  the  sounds  of  letters  into  words, 
and  even  into  sentences,  a  convincing  proof  not  only  of  the  mechanical 
nature  of  articulate  sounds,  but  also  of  the  perfect  manner  in  which  the 
natural  mechanism  is  understood.  Animals  which  have  been  taught  to 
speak  may  also  be  regarded  as  automata,  for  they  have  no  comprehen- 
sion of  what  it  is  they  are  uttering,  and  never  produce  articulate  com- 
binations spontaneously,  but  only  as  the  result  of  instruction. 

Like  the  automata  just  alluded  to,  the  human  voice  expresses  words 
Words  originate  ^v  combining  their  constituent  letters  together.  Gramma- 
by  combining  rians  divide  letters  into  two  groups,  vowels  and  consonants, 
defining  the  vowel  as  a  sound  that  can  be  uttered  by  itself, 
the  consonant  taking  its  name'  from  the  fact  that  it  can  only  be  uttered 
consonantly  with  a  vowel.  By  personal  experiment,  it  may  be  easily 
proved  that  the  vowel  is  a  continuous  sound,  which  may  be  kept  up  just 
as  long  as  the  breath  will  enable,  and,  on  examining  the  position  of  the 
Consonants  tongue  and  other  movable  portions  of  the  mouth,  the  particular 
and  vowels,  arrangement  necessary  for  pronouncing  the  letters  #,  0,  z,  o,  u, 
or  the  sixteen  or  eighteen  vowel  sounds  of  the  Continental  languages,  will 
be  detected.  It  will  be  found  that  the  determining  condition  is,  for  the 
most  part,  the  peculiar  modification  of  the  oral  apertures.  It  will  also 
be  discovered  that  articulation  is  wholly  independent  of  the  larynx,  since 
merely  by  expelling  the  air  through  the  mouth,  without  permitting  any 
laryngeal  sound  to  be  formed,  all  the  letters  may  be  articulated  in  a  whis- 
per. M.  Deleau  has  illustrated  this  fact  in  an  ingenious  way  by  put- 
ting an  India-rubber  tube  through  the  nostril,  so  as  to  reach  the  poste- 
rior portion  of  the  mouth,  and  causing  another  individual  to  blow  gently 
through  it ;  while  the  organs  of  the  mouth  are  silently  thrown  into  those 
Nature  of  whis-  positions  necessary  for  the  utterance  of  any  particular  sound, 
penng.  t^at  articulate  sound  will  at  once  appear  in  whispers ;  but 

if,  while  this  is  being  done,  the  larynx  is  permitted  to  yield  a  sound,  two 
voices  then  are  heard,  one  in  audible  speech  and  one  in  a  whisper,  the 


NATURE   OF  LANGUAGES.  357 

former  belonging  to  the  individual  who  is  making  the  experiment,  and 
the  other  arising  from  the  air  which  his  companion  is  blowing  into  the 
tube.  There  is  no  kind  of  difficulty  in  constructing  a  simple  kind  of  in- 
strument from  which  the  sounds  of  the  vowels  can  be  produced  by  gen- 
tly blowing  air  into  it. 

The  consonants  are  of  two  kinds,  the  explosive  and  continuous.  The 
former  arise  from  an  abrupt  and  momentary  action,  and  dis-  Explosive  and 
appear  at  once;  as  examples  of  these,  the  letters  b,  d,p,  in  continuous  con- 
which  it  may  be  remarked  that  the  characteristic  of  the 
sound  disappears  in  an  instant ;  hence  the  term  explosive ;  and  if  any 
attempt  be  made  to  continue  it,  it  issues  in  the  utterance  of  the  vowel  e  ; 
but  in  the  continuous  consonants  this  does  not  take  place,  as  in  the  let- 
ters n,f,  s.  In  the  case  of  the  consonants,  as  in  that  of  the  vowels,  the 
peculiar  arrangement  of  the  parts  of  the  mouth,  though  difficult  to  de- 
scribe, may  be  readily  ascertained  by  personal  experiment. 

Of  vocal  sounds  thus  originating,  it  may  be  remarked,  .that  in  the  low- 
er tribes  of  animals,  their  chief  use  seems  to  have  reference  to  Use  of  the 
the  perpetuation  of  the  race.  Even  in  the  highest,  the  changes  voice  of  ani- 
of  the  reproductive  and  vocal  organs  often  occur  contempora- 
neously ;  but,  though  this  may  be  true  of  mere  sounds,  the  modulated 
variations  thereof  have  a  far  more  general  use.  Of  languages  it  may  be 
said  that  they  are  the  creation  of  groups  or  nations  of  .men,  not  of  indi- 
viduals, and  hence  they  reach  beyond  the  compass  of  indi-  of  languages: 
vidual  life,  in  some  instances  having  endured  for  thousands  their  duration, 
of  years.  Moreover,  if  critically  considered,  each  often  contains  the  his- 
tory of  the  race  by  which  it  is  spoken,  and  even  manifests  the  broader 
features  of  its  character ;  so  our  own  tongue  contains  the  indications  of 
the  two  chief  political  events  which  have  befallen  the  English  nation,  at 
least  so  far  as  foreign  relations  are  concerned — the  conquest  of  Britain  by 
the  Komans,  and,  a  thousand  years  after,  by  the  French.  In  conse- 
quence of  the  first  of  these  events,  the  language  became,  so  far  as  com- 
mon expressions  are  concerned,  almost  bi-lingual.  Such  simple  illustra- 
tions as  the  words  God,  deity ;  fatherly,  paternal ;  motherly,  maternal ; 
heavenly,  celestial ;  earthly,  terrestrial ;  hellish,  infernal ;  womanly,  fem- 
inine, may  serve  as  examples.  So  well  recognized  are  these  principles 
among  linguists  that  they  are  resorted  to  for  the  decision  of  pre-historic- 
al  questions.  The  best  and  most  precise  evidence  that  we  have  of  the 
Indian  origin  of  the  German  nations  is  derived  from  the  occurrence  of 
Sanscrit  roots  in  their  vocabulary,  and  analogies  in  their  grammar.  The 
names  of  many  domestic  animals,  of  farming  implements,  and  of  many 
common  objects,  are  the  same  in  Sanscrit,  Latin,  Greek,  and  German. 

Nay,  even  more  than  this,  from  the  structure  of  a  language,  collated 
with  the  history  of  the  people  by  which  it  is  spoken,  we  can  often  judge 


358  NATURE   OF   LANGUAGES. 

Connection  of  °f  tne  influence  of  events  more  perfectly  than  in  any  other 
language  with  wav •  so  in  the  two  instances  which  we  are  referring  to  as 
toitie^Sd011 "  illustrations  of  these  remarks,  the  French  conquest  did  not 
history.  make  that  deep  and  abiding  impression  which  the  Roman  one 

had  done.  -  A  thousand  years  had  elapsed  between  the  invasion  of  Ca3sar 
and  that  of  William  of  Normandy,  eight  hundred  only  from  the  latter 
event  to  our  times,  yet  the  influence  of  the  masculine  and  civilizing  Ro- 
man has  reached  through  that  long  interval,  has  made  the  deepest  im- 
pression en  the  national  character,  and  is  manifested  in  almost  one  half 
of  the  sentences  that  we  utter. 

Connected  with  articulate  speech,  it  may  not  be  out  of  place  to  allude 
Registry  of  briefly  to  those  great  advances  which  have  been  made  by  the 
in^a^d^rtnf"  genms  °^  man  in  tne  permanent  record  or  registering  by 
ing.  written  signs  ;  and  as  sounds  are  of  two  kinds,  musical  and 

articulate,  so  we  have  two  distinct  methods  of  writing  ;  and  this,  leaving 
out  all  the  earlier  and  more  imperfect  forms,  a  method  for  music  and  one 
for  speech.  Of  the  former,  it  is  scarcely  necessary  to  remark  that  it  is 
universal ;  the  combination  of  sounds  designed  to  be  conveyed  is  com- 
prehended at  once  by  men  of  every  nation ;  but  in  the  writing  for  speech, 
various  methods  have  been  employed  at  different  times  and  by  different 
Different  meth  nati°ns>  ^rom  mere  picture  writing,  each  sign  of  which  called 
ods  of  express-  forth  in  different  languages  different  sounds,  through  the  hi- 
ing  language.  er0giyphic  and  Chinese  methods  up  to  that  most  splendid 
invention  of  later  ages,  alphabetic  writing,  the  principle  of  which  is  ab- 
solutely perfect,  because  it  is  natural,  being  to  decompose  each  word  into 
each  constituent  vowel  or  consonant  sound  which  it  contains,  and  to 
write  a  mark  or  letter  representing  each  of  those  sounds.  Though  many 
circumstances  have  contributed  to  the  advancement  of  the  human  race,  it 
can  not  be  doubted  that  this  invention  has  exceeded  all  others  in  power, 
and  that  alphabetic  writing  has  been  the  great  instrument  of  civilization. 


OF   THE   SENSES.  359 


CHAPTER  XIX. 

OF  HEAEING. 

The  Senses:  General  Remarks  upon. — Five  Organs  of  Sense. — Necessity  of  Apparatus  for  the 
Appreciation  of  Time,  Space,  Pressure,  Temperature,  and  Chemical  Qualities. 

Of  Hearing. — General  Structure  of  the  Organ  of  Hearing. — Physical  Peculiarities  of  Sounds,  In- 
tensity, Time  of  Vibration,  and  Quality. — The  Tympanum,  Cochlea,  and  Semicircular  Canals 
are  for  the  Appreciation  of  these  peculiarities. 

Structure  and  Functions  of  the  Tympanum,  or  Measurement  of  Intensity. 

Structure  of  the  Cochlea,  its  Spiral  Lamina  and  Scalce. — Measures  the  Time  of  Vibration. — Ac- 
complishment of  Interference  in  the  Scalce. —  Comparative  Anatomy  of  the  Cochlea. 

Structure  of  the  Semicircular  Canals. — They  estimate  the  Quality  of  Sounds. 

Comparative  Anatomy  of  the  Auditory  Mechanism. — Its  Progress  in  Development. — Imperfection 
of  the  Doctrine  of  Means  and  Ends. 

OF  THE  SENSES. 

THE  organs  and  functions  which  have  thus  far  been  described  have 
reference,  for  the  most  part,  to  the  conservation  of  the  indi-  Function  of 
vidual  being,  maintaining  its  structure  unimpaired,  notwith-  the  senses- 
standing  the  waste  it  is  perpetually  undergoing,  or  conducting  its  devel- 
opment. We  now  enter  on  the  consideration  of  a  totally  distinct  ap- 
paratus, the  object  of  which  is  to  put  the  individual  in  relation  with  ex- 
ternal nature,  and  to  which,  therefore,  the  designation  of  mechanism  of 
external  relation  may  be  appropriately  given. 

For  the  sentient  being  in  its  highest  development,  means  must  be  pro- 
vided for  the  perception  of  time,  space,  force,  and  quality.  Five  organs 
This  is  accomplished  by  what  are  termed  the  organs  of  sense.  of  sense- 
They  are  five  in  number :  1st.  The  organ  of  hearing ;  2d.  That  of  see- 
ing ;  3d.  That  of  touching ;  4th.  That  of  smelling ;  5th.  That  of  tasting. 
In  the  further  description  of  the  senses,  it  will  be  found  that  the  ear  is 
the  organ  of  time ;  the  eye  that  of  space ;  the  tactile  apparatus  is  for  the 
perception  offeree ;  and  that  the  mechanism  for  smelling  and  tasting  con- 
jointly determine  the  chemical  qualities  of  bodies ;  that  of  smelling  ad- 
dressing itself  to  substances  which  are  in  the  vaporous  and  gaseous  state ; 
and  that  of  tasting,  to  such  as  are  liquid  or  dissolved  in  water. 

We  shall  pursue  the  description  of  the  senses  in  the  order  in  which 
they  have  been  just  enumerated,  premising  of  them  respect-  The  ear  is  the 
ively  that,  the  function  of  hearing  being  the  reception  of  the  orsan  of  time- 
succession  of  sounds,  periods  of  silence,  musical  notes,  and  their  modu- 
lations, together  with  the  peculiarities  of  articulate  speech,  things  which 
are  all  inherently  and  essentially  connected  with  the  lapse  of  time,  the 


360  OF   HEARING. 

The  eye  is  the  ear  is  in  a  philosophical  sense  the  time  organ ;  that,  the  func- 
organ  of  space,  ^ion  of  the  eye  being  the  estimation  of  extents,  the  position 
of  objects,  their  sizes  and  apparent  distances,  this  apparatus  is,  in  reality, 
the  space  organ,  its  indications  in  this  particular  being  rendered  more 
perspicuous  and  more  intense  by  its  quality  of  being  affected  by  varia- 
tions of  color ;  that  as  the  tactile  mechanism  is  affected  by  extraneous 
Touch  is  for  ^orces»  sucn  as  pressures,  estimating  their  degree  of  power,  and 
pressure  and  being  likewise  influenced  by  things  which  are  at  a  distance, 
temperature.  ^  temperatures  Of  wnicn  are  different  from  the  standard 
which  it  observes,  but  not  by  electrical,  magnetic,  or  luminous  agencies, 
we  may  infer  that  its  functions  are  limited  to  a  relation  with  mechanical 
Smell  and  taste  powers,  strictly  speaking,  and  to  heat;  that  smell  and  taste, 

for  chemical      though  conveniently  treated  of  as  separate  functions,  de- 
qualities  of  gas-          °  .         *  .  ' 
es  and  liquids  pendent  on  separate  organs,  are,  in  reality,  allied  in  the  de- 

respectiveiy.  termination  of  the  chemical  peculiarities  of  bodies,  and  re- 
spectively adapted  to  the  appreciation  of  those  peculiarities,  according  as 
the  substance  presented  may  have  the  gaseous  or  liquid  form. 

OF  HEAEING. 

The  organ  of  hearing  is  composed  of  three  parts,  the  external  ear,  the 
tympanic  cavity  or  tympanum,  and  the  labyrinth. 

The  external  ear  consists  of,  1st.  The  pinna,  which  is  for  the  purpose 
Oftheexter-  °f  collecting  soniferous  waves,  and  directing  them  into,  2d. 
nal  ear.  The  meatus  auditorius  or  auditory  canal,  a  tube  about  an  inch 
long,  and  extending  to  the  tympanum.  It  is  not  perfectly  cylindrical, 
its  vertical  diameter  being  the  greatest,  and  it  is  curved  so  as  to  be  con- 
cave downward.  The  interior  is  protected  by  hairs,  and  by  a  waxy  se- 
cretion of  the  ceruminous  glands. 

The  tympanum,  tympanic  cavity,  or  middle  ear,  is  within  the  petrous 
Ofthetympa-  tone.  It  is  bounded  exteriorly  by  a  thin  oval  membrane, 
num-  the  membrana  tympani,  which  is  placed  obliquely  across  the 

meatus,  at  an  angle  of  about  45  degrees,  its  outward  plane  looking  down- 
ward. Across  the  tympanum  there  is  a  chain  of  three  small  bones,  the 
malleus  or  hammer,,  the  incus  or  anvil,  and  the  stapes  or  stirrup.  The 
malleus  is  attached  by  its  handle  to  the  membrana  tympani,  and  the 
stapes,  which  is  at  the  other  extreme  of  the  chain,  is  fastened  by  its  foot- 
plate to  the  membrane  of  the  fenestra  ovalis.  To  the  short  process  of 
the  malleus,  the  tendon  of  the  tensor  tympani  is  attached,  and  to  the  neck 
of  the  stapes  the  stapedius.  Besides  these,  other  muscles  of  the  tympa- 
nic cavity  may  be  doubtfully  mentioned,  as  the  external  muscle  or  laxa- 
tor  tympani,  and  the  laxator  tympani  minor.  Into  the  tympanic  cavity 
there  are  ten  openings,  of  which  the  more  important  ones  are,  1st.  That  of 
the  meatus  auditorius ;  2d.  The  fenestra  ovalis,  which  is  of  an  elliptic 


STRUCTURE  OF  THE  EAK.  361 

shape  and  opposite  the  preceding,  the  foot-plate  of  the  stapes,  as  has  been 
said,  being  placed  upon  it ;  it  is  also  sometimes  called  fenestra  vestibuli ; 
3d.  Fenestra  rotunda,  which  is  below  the  preceding,  and  separated  from 
it  by  the  promontory.  From  the  circumstance  that  it  leads  from  the 
tympanum  to  the  cochlea,  it  is  also  called  fenestra  cochlea? :  like  the  pre- 
ceding, it  is  closed  by  a  double  membrane ;  4th.  The  Eustachian  tube, 
which  extends  from  the  anterior  of  the  tympanum  to  the  pharynx ;  and, 
5th.  The  mastoid  cells.  The  smaller  openings  are  for  the  passage  of  va- 
rious nerves  and  muscles. 

The  labyrinth,  called  likewise  the  internal  ear,  consists  of  three  parts, 
.the  vestibule,  the  semicircular  canals,  and  the  cochlea. 

The  vestibule  has  three  corners,  an  anterior,  a  superior,  and  a  poste- 
rior, termed  its  ventricles.  There  open  into  it  the  fenestra  oftheiaby- 
ovalis,  the  scala  vestibuli,  and  the  five  openings  of  the  three  sem-  rinth- 
icircular  canals.  Besides  these  there  are  some  smaller  ones,  as  the  aque- 
duct of  the  vestibule,  and  foramina  for  small  arteries,  and  for  the  branch- 
es of  the  auditory  nerve.  The  semicircular  canals  are  three  bony  semi- 
circles opening  into  the  vestibule :  upon  one  of  the  branches  of  each  there 
is  a  dilatation,  the  ampulla.  The  three  canals  are  respectively  placed  in 
planes  at  right  angles  to  each  other.  The  cochlea  is  a  spiral  bony  canal 
raised  upon  a  central  axis,  the  modiolus  :  its  interior  is  divided  into  two 
passages  or  scalar  by  the  lamina  spiralis.  These  communicate  at  the 
apex  of  the  cochlea  through  a  small  aperture,  their  other  extremities 
opening  differently ;  the  scala  vestibuli  into  the  anterior  ventricle  of  the 
vestibule,  and  the  scala  tympani  through  the  fenestra  rotunda  into  the 
tympanum.  The  labyrinth  contains  interiorly  a  membrane,  the  mem- 
branous labyrinth.  Between  the  membranous  labyrinth  and  the  bony, 
a  liquid,  the  perilymph,  intervenes  ;  the  membranous  labyrinth  being 
also  filled  with  liquid,  the  endolymph.  There  is  no  perilymph  in  the 
cochlea. 

Of  the  three  portions  of  the  ear,  the  external  canal  is,  of  course,  full 
of  air,  as  is  also  the  tympanic  cavity  or  drum ;  but  the  labyrinth,  as  we 
have  seen,  is  filled  with  a  liquid,  and  in  this  the  terminal  filaments  of 
the  auditory  nerve  are  placed. 

The  essential  part  of  the  mechanism  of  hearing  is  the  auditory  nerve, 
which  arises  from  the  anterior  wall  of  the  fourth  ventricle,  of  the  audi- 
and  then,  joining  the  facial,  passes  forward  upon  the  crus  cer-  '  torJ -nerve. 
ebelli ;  reaching  tha  meatus,  it  divides  into  two  portions,  the  cochlear  and 
vestibular  nerves,  which  subdivide  again,  and  are  distributed  to  the  ves- 
tibule and  cochlea  respectively  in  the  manner  hereafter  explained. 

VIEW   OF  EXTERNAL,  MIDDLE,  AND   INTERNAL  EAR. 

Fig.  183  :  #,  #,  pavilion  and  external  auditory  canal,  or  external  ear ; 


362 


STRUCTURE   OF   THE   EAR. 


Fig.  1S3. 


External,  middle,  and  internal  ear. 


#,  tympanic  cavity,  containing  the  bones ; 

c,  hammer  and  its  three  muscles,  viz., 

d,  internal  muscle,  lodged  in  the  thick- 
ness of  the  superior  wall  of  Eustachian 
tube,  and  bending  at  a  right  angle  to  be 
inserted  in  superior  part  of  handle  of 
hammer ;  e,  anterior  muscle  of 'hammer; 
jf,  external  muscle  of  hammer ;  g,  inte- 
rior half  of  membrana  tympani,  holding 
the  handle  of  the  hammer ;  A,  tube  of 
Eustachius  ;  i,  internal  ear  or  labyrinth. 


Tympanic  cavity. 


TYMPANIC   CAVITY,  ITS   BONES,  MUSCLES,  AND  NERVES. 

Pig.  184 :  «,  hammer,  holding,  by  the  anterior  and  superior  part  of  its 

handle,  and  by  its  round  extremity,  #,  the 
membrana  tympani ;  <?,  internal  muscle  of 
hammer ;  d,  stirrup  upon  fenestra  ovalis  ; 
0,  muscle  of  stirrup ;  1,  facial  nerve,  com- 
municating with,  2,  great  superficial  pe- 
trosal,  and,  3,  little  superficial  petrosal ; 
4,  chorda  tympani ;  5,  5,  nervous  twig  of 
internal  muscle  of  hammer,  arising  from 
motor  portion  of  fifth  pair,  and  traversing  otic  ganglion ;  6,  nervous  twig, 
arising  from  facial  and  going  to  muscle  of  stirrup ;  7,  ganglion  of  Gasser. 

DIAGRAM    SHOWING  THE   FACIAL   IN   THE   AQUEDUCT  OF   FALLOPIUS  AND   ITS   ANASTOMOSES. 

Fig.  185 :   1,  facial ;  2,  nerve  of  Wrisberg ;  3,  petrosal  twig  of  vidian 
Fig.  185.  nerve ;   4,  ganglion  of  Meckel ;  5,  little 

petrosal  of  Longet ;  6,  twig  of  muscle  of 
stirrup;  7,  auricular  twig  of  Arnold ;  8, 
chorda  tympani,  cut ;  9,  ganglion  of  An- 
dersch  ;    10,  nerve  of  Jacobson,  divided 
into  six  twigs,  viz.,  11,  twig  anastomos- 
ing   with,  12,  carotid   plexus,  13,  twig 
anastomosing  with  great  superficial  pe- 
Faciai  in  the  aqueduct  of  Faiiopius.        trosal  (little  deep  petrosal  of  Arnold),  14, 
little  superficial  of  Arnold,  uniting  with  little  petrosal  of  Longet  to  form 
15,  a  common  trunk,  which  goes  to  16,  otic  ganglion ;   17,  twig  of  fenes- 
tra rotunda ;  18,  twig  of  fenestra  ovalis  ;  19,  twig  of  tube  of  Eustachius. 
The  explanation  usually  given  of  the  functions  of  these  various  parts 
Common  hy-     is  as  follows  :  The  waves  of  sound,  moving  through  the  at- 
functSn  of  the  Biosphere,  pass  down  the  exterior  canal  and  strike  upon  the 
auditory  parts,  membrane  of  the  drum,  which  is  thrown  into  vibration  there- 


PEOPERTIES    OF   SOUND.  363 

by.  The  little  bones  which  form  a  chain  from  this  membrane  to  the  oval 
one  at  the  back  of  the  drum  participate  in  this  movement,  and,  indeed, 
serve  to  convey  it,  without  much  loss,  across  the  cavity.  It  is  consider- 
ed that  this  is  their  function,  since  it  may  be  proved  experimentally  that 
wave  sounds  going  through  such  a  solid  combination,  surrounded  by  at- 
mospheric air,  pass  with  but  very  little  loss  of  intensity.  Under  the  im- 
pulses thus  communicated  to  it,  the  oval  membrane  commences  to  vi- 
brate, and  in  those  movements  the  water  in  the  labyrinth  joins ;  and  so 
the  filaments  of  the  auditory  nerve  become  aifected,  and  the  sensation  of 
sound  is  transmitted  to  the  brain.  It  is  supposed  that  the  three  semi- 
circular canals,  which  are  set  at  right  angles  to  one  another,  as  it  were, 
occupying  the  three  adjoining  faces  of  a  cube,  are  for  the  purpose  of  de- 
termining in  what  direction  the  sound  is  coming — whether  upward,  down- 
ward, or  laterally.  Moreover,  it  is  believed  that  the  little  muscles  winch 
operate  on  the  membrane  of  the  drum  have  the  duty  of  tightening  or 
slackening  it  so  as  to  receive  the  sounding  waves  in  the  most  available 
way. 

It  is  not  necessary  to  enter  on  a  lengthy  criticism  of  this  explanation. 
Physiologists  have  long  regretted  that  it  assigns  no  use  for  Criticisms  on 
many  of  the  most  complicated  and  delicate  arrangements  con-  this  hypothe- 
nected  with  the  ear,  offers  no  explanation  of  the  manner  in  S1S' 
which  that  intricate  organ  is  enabled  to  present  to  the  mind  the  various 
relations  of  sound,  and  is  inconsistent  with  many  of  the  facts  of  compar- 
ative anatomy.  Indeed,  it  is  very  plain  that  a  true  interpretation  of  the 
action  of  the  different  regions  and  structures  of  the  ear  can  only  be  given 
from  a  conjoint  study  of  the  physical  nature  and  properties  of  sounds,  of 
the  peculiarities  of  the  soniferous  waves  which  it  is  necessary  pr0permodeof 
for  us  to  perceive,  of  the  comparative  anatomy  of  the  ear  as  obtaining  a 

i  •        11  ,   -1  ri't*  i  ^  ,  t  true  interpret- 

presented  in  all  tribes  ol  liie ;  and,  since  mere  must  be  a  cor-  ation  of  these 
respondence  among  the  lower  tribes — perhaps  we  might  have  functions- 
said  the  higher  too — between  the  organs  of  voice  and  the  organs  of  audi- 
tion, the  obscure  points  in  the  structure  of  the  latter  may  be  illustrated 
by  what  is  known  of  the  former.     To  these  might  be  added  the  study  of 
its  embryonic  development.     It  is  by  the  aid  of  these  different  means 
that  I  pass  to  the  description  of  the  function  of  audition. 

What,  then,  are  the  physical  peculiarities  existing  in  the  waves  of 
sound  which  we  actually  perceive?  They  are  these  three,  Three  hvsical 
1st.  The  intensity,  that  is,  loudness  or  feebleness  of  the  peculiarities  of 
sound;  2d.  Its  note  or  pitch;  3d.  Its  quality;  for  two  sounds  s< 
of  the  same  intensity  and  note  may  differ  characteristically.  The  sound 
of  the  violin  differs  from  that  of  the  flute,  and  this,  again,  from  that  of 
the  human  voice.  Our  organ  of  audition  is  so  constructed  that  it  is  af- 
fected by  each  of  these  peculiarities,  and  transmits  them  to  the  mind. 


364  STKUCTUEE    OF   THE   DEUM. 

In  this  respect  we  may  speak  of  it  as  a  perfect  organ ;  for  all  mathemati- 
cians who  have  written  on  the  subject  of  sound  agree  in  setting  forth  the 
three  peculiarities  that  have  "been  mentioned,  intensity,  note,'  quality,  as 
the  grand  features  of  waves  of  sound,  and  this  upon  a  mere  abstract  dis- 
cussion of  acoustics.  Now  these  three  essential,  abstract,  or  theoretical 
peculiarities  of  sound-waves  are  the  very  three  which  the  organ  of  hear- 
ing seizes  upon,  and  so  we  are  justified  in  saying  that,  in  this  respect,  it 
is  perfect  in  its  construction.  Premising  the  remark  that  mathemati- 
cians have  abundantly  proved  that  the  intensity  of  sounds  depends  upon 
the  amplitude  of  excursion  of  the  vibrating  particles,  and  the  pitch  or  note 
upon  wave  length,  I  shall  now  proceed  to  offer  some  arguments  in  proof  of 
the  proposition  that  the  triple  function  of  the  ear  is  discharged  in  the  fol- 
Functionofthe  l°wmg  way :  1^.  That  the  drum  is  for  the  measurement  of 
drum,  cochlea,  intensity;  2d.  The  cochlea  for  the  recognition  of  wave  length; 

canals.  ^  ^Q  semicircular  canals  for  the  appreciation  of  quality. 
I  shall  endeavor  to  show  that  the  ear  is  not  a  homogeneous  organ,  as  the 
older  hypothesis  supposed,  but  that  one  or  other  of  these  instrumental 
parts  may  be  absent,  and  with  it  will  disappear  its'  special  function,  forti- 
fying this  view  with  facts  presented  by  comparative  anatomy,  by  embry- 
onic development,  and  also  by  the  relations  of  the  voice,  and  showing 
the  parallel  between  the  structure  and  functions  of  the  ear,  the  organ  for 
normal  vibrations,  and  of  the  eye,  the  organ  for  transverse  ones  ;  and  the 
analogy  and  the  identity  of  their  embryonic  development ;  that,  for  in- 
stance, the  drum  is  the  equivalent  of  the  iris,  and  the  cochlea  of  the  ret- 
ina and  its  adjacent  parts. 

1st.  On  the  measurement  of  the  intensity  of  sound,  structure  of  the 
tympanic  cavity  or  drum,  and  its  functions. 

The  tympanic  cavity  or  drum  of  the  ear,  as  we  have  briefly  described, 
Structure  of  *s  an  a^r  cav^7  °^  a  cylindroid  and  flattened  shape,  in  the 
the  drum  and  petrous  portion  of  the  temporal  bone.  Outwardly  it  is 
its  functions.  bounded  ^y  the  membrana  tympani,  and  on  other  sides  by 
the  petrous  bone :  it  is  crossed  by  a  chain  of  bones,  three  in  number,  and 
named  the  malleus  or  hammer-bone,  the  incus  or  anvil,  and  the  stapes 
or  stirrup.  The  Eustachian  tube  affords  a  channel  of  communication 
from  the  interior  of  the  drum  to  the  pharynx.  Moreover,  there  is  a  com- 
munication with  the  mastoid  cells,  but  the  Eustachian  tube  is  the  only 
outlet  to  the  atmosphere.  The  whole  cavity  of  the  tympanum  is  lined 
with  mucous  membrane  and  ciliated  epithelium,  which  is  also  reflected 
over  the  bony  chain.  Upon  the  inner  wall  of  the  tympanum  are  two 
chief  apertures,  the  fenestra  ovalis  and  the  fenestra  rotunda,  each  closed 
by  membrane.  The  chain  of  bones  is  attached  at  one  end  by  the  handle 
of  the  malleus  to  the  membrana  tympani,  at  the  other  by  the  foot  of  the 
stirrup  to  the  membrane  of  the  fenestra  ovalis. 


ACTION   OF  THE   EAR  MUSCLES.  365 

It  is  to  be  remarked  that  the  membrana  tympani  is  placed  obliquely 
at  the  bottom  of  the  external  canal.  In  a  hollow  bony  cone,  Action  of  the 
rising  upon  the  interior  wall  of  the  tympanum,  and  called  the  tensor'tym-* 
pyramid,  the  stapedius  muscle  is  placed.  Through  a  little  pani. 
aperture  at  the  apex  of  the  pyramid  its  tendon  goes  out,  and  is  inserted 
in  the  neck  of  the  stapes.  Its  action  seems  to  be  to  make  pressure  on 
the  membrane  of  the  fenestra  ovalis,  but  as  it  does  this,  it  tilts  the  stapes 
into  an  oblique  position.  A  second  muscle,  the  Censor  tympani,  is  at- 
tached in  front  to  the  under  surface  of  the  petrous  bone,  and  is  inserted 
in  the  short  process  of  the  malleus ;  when  it  contracts  it  makes  tension 
upon  the  membrana  tympani,  drawing  it  more  tightly  inward.  It  is  to 
be  especially  remarked  of  both  these  muscles  that  they  are  voluntary ; 
that  is,  of  the  striated  variety.  Two  other  muscles  are  described  by 
some  anatomists,  and  have  been  indicated  in  Fig.  183  and  184.  Their 
existence,  however,  is  disputed  by  others. 

In  the  opinion  of  Mr.  Toynbee,  the  action  of  the  two  voluntary  mus- 
cles of  the  ear  is  as  follows.  By  the  tensor  tympani  the  Mr.Toynbee's 
base  of  the  stapes  is  pressed  inward  to  ward  the  vestibule,  as  views  of  the  ac- 

_.r  n  _  ,  ,  tionof  the  sta- 

is  a  piston  in  its  cylinder,  and,  as  soon  as  the  muscle  ceases  pediusandten- 
to  act,  the  elastic  ligaments  which  attach  the  circumference  sor  ^P*111- 
of  the  base  of  the  stapes  to  that  of  the  fenestra  ovalis  draw  it  out  again. 
The  stapes  is  moved  by  two  muscles,  the  tensor  tympani  and  the  stape- 
dius, it  being  commonly  supposed  that  the  latter. aids  the  former  in  press- 
ing the  stapes  inward,  but  he  shows  that  it  rotates' the  base  of  the  stapes 
and  withdraws  it  from  the  cavity  of  the  vestibule.  This  may  be  demon- 
strated by  pulling  the  stapediusj  when  the  fluid  in  the  scala  vestibuli 
will  be  found  to  move  correspondingly.  He  therefore  asserts  that  the 
stapedius  is  the  antagonist  of  the  tensor,  the  former  relaxing  the  laby- 
rinthine fluid,  membrana  rotunda,  and  membrana  tympani,  the  latter 
rendering  them  more  tense.  Agreeably  to  this,  the  stapedius  is  supplied 
from  the  portio  dura,  and  the  tensor  from  the  otic  ganglion.  This  con- 
struction might  lead  to  the  supposition  that  the  tensor  affords  protection 
from  loud  sounds,  and  the  stapedius  enables  the  most  delicate  whisper  to 
be  heard,  as  in  listening.  Together  they  regulate  the  amount  of  sono- 
rous vibrations  which  enter  the  labyrinth.  Hence  the  effect  of  the  de- 
struction of  the  membrana  tympani  is  to  make  sounds  unendurable.  In 
confirmation  of  this  is  quoted  the  case  of  a  patient  who,  under  those  cir- 
cumstances, could  not  bear  the  whistling  of  another  patient  in  an  adjoin- 
ing bed,  and  the  observation  of  Cheselden  that  a  dog,  in  which  both 
membrana3  tympani  had  been  destroyed,  for  some  time  received  strong 
sounds  with  horror. 

We  shall  now  present  some  reasons  for  supposing  that  the  function 
of  the  tympanum  is  for  determining  the  first  property  of  sounding  waves, 
that  is,  their  intensity. 


366  EFFECTS    OF   TENSION    OF   THE   TYMPANUM. 

It  has  been  proved  by  the  experiments  of  Savart  and  Miiller,  that 
Ofthedeterm-  when  the  tension  of  the  membrana  tympani  is  increased,  so- 
ination  of  the  norous  undulations  pass  with  less  readiness  through  it.  In- 

intensity  of  so- 

niferouswaves.  deed,  this  may  be  yenned  by  personal  experiment,  as  when, 
by  a  strong  effort  of  .expiration  or  inspiration,  the  mouth  and  nostrils  be- 
ing closed,  we  compress  air  into  the  tympanic  cavity  or  withdraw  it  there- 
from through  the  Eustachian  tube,  and  thereby  stretch  the  membrana 
tympani  outwardly  or  inwardly,  the  hearing  at  once  becomes  indistinct, 
and  sounds  are  enfeebled.  The  same  ensues  on  going  down  in  a  diving- 
bell,  or  suddenly  ascending  in  a  balloon.  Of  the  former  effect,  Dr.  Col- 
Deafness  in  the  ladon  gives  the  following  account  during  a  descent  in  a  div- 
diving-beii.  ing-bell  at  Howth  in  1820.  "We  descended,"  says  he, 
"  so  slowly  that  we  did  not  notice  the  motion  of  the  bell ;  but  as  soon 
as  the  bell  was  immersed  in  water,  we  felt  about  the  ears  and  forehead  a 
sense  of  pressure,  which  continued  increasing  during  some  minutes.  I  did 
not,  however,  experience  any  pain  in  the  ears,  but  my  companion  suffered 
so  much  that  we  were  obliged  to  stop  our  descent  for  a  short  time.  To 
remedy. that  inconvenience,  the  workmen  instructed  us,  after  having  closed 
our  nostrils  and  mouth,  to  endeavor  to  swallow,  and  to  restrain  our  respi- 
ration for  some  moments,  in  order  that,  by  this  exertion,  the  external  air 
might  act  on  the  Eustachian  tube.  My  companion,  however,  having  tried 
it,  found  himself  very  little  relieved  by  this  remedy.  After  some  minutes 
we  resumed  our  descent.  My  friend  suffered  considerably :  he  was  pale ; 
his  lips  were  totally  discolored ;  his  appearance  was  that  of  a  man  on  the 
point  of  fainting ;  he  was  in  involuntary  low  spirits,  owing  perhaps  to  the 
violence  of  the  pain,  added  to  that  kind  of  apprehension  which  our  situa- 
tion unavoidably  inspired.  This  appeared  to  me  the  more  remarkable,  as 
my  case  was  totally  the  reverse.  I  was  in  a  state  of  excitement  resem- 
bling the  effect  of  some  spirituous  liquor.  I  suffered  no  pain.  I  expe- 
rienced only  a  strong  pressure  around  my  head,  as  if  an  iron  circle  had 
been  bound  about  it.  I  spoke  with  the  workmen,  and  had  some  diffi- 
culty in  hearing  them.  This  difficulty  of  hearing  rose  to  such  a  height 
that  during  three  or  four  minutes  I  could  not  hear  them  speak.  I  could 
not,  indeed,  hear  myself  speak,  though  I  spoke  as  loudly  as  possible, 
nor  did  even  the  great  noise  caused  by  the  violence  of  the  current  against 
the  sides  of -the  bell  reach  my  ears." 

Under  natural  circumstances,  a  stretching  of  the  membrane  inwardly 
Action  of  the  *s  accomplisne(l  by  the  contraction  of  the  tensor  tympani  mus- 
musciesofthe  cle,  the  stapedius  holding  tight  contemporaneously  on  the 
loop  of  the  stirrup,  and  preventing  disturbance  of  position  of 
the  bony  chain  at  that  end,  and  hindering  any  outward  bulging  of  the 
membrane  of  the  fenestra  ovalis.  When,  therefore,  the  soniferous  waves 
impinge  upon  the  membrana  tympani,  they  tend  to  throw  it  into  vibra- 


THE   EUSTACHIAN  TUBE.  367 

tion ;  the  tensor  tympani  contracts  to  such  an  extent  as  to  bring  the 
membrane  to  a  standard  of  tension,  and,  since  this  muscle  is  of  the  vol- 
untary kind,  the  mind  judges  of  fhe  degree  of  force  which  is  required  to 
produce  that  result  just  as,  when  we  lift  from  the  ground  bodies  of  dif- 
ferent weights,  we  judge  with  a  certain  precision  of  the  degree  of  force 
necessary  to  be  put  forth.  The  condition  of  contraction  of  the  tensor 
tympani  therefore  enables  the  mind  to  measure  the  intensity  of  the  sound- 
ing waves. 

But  this  muscular  contraction  is  strictly  a  reflex  act,  and  is  therefore 
preceded,  as  all  such  acts  are,  by  an  impression.  That  impression  is 
made,  as  we  shall  presently  find,  primarily  on  the  auditory  nerve.  But 
since  these  reflected  acts  are  not  sensory,  the  mind  has  no  knowledge  of 
the  effect  impressed  in  this  respect  upon  the  auditory  nerve,  and  only  be- 
comes sensible  of  it  in  an  indirect  way,  through  the  contractions  which 
have  ensued  in  the  tensor  tympani  muscle. 

In  this  view  of  the  case,  the  use  of  the  Eustachian  tube  becomes  ob- 
vious ;  it  is  to  form  a  ready  passage  for  the  air  inwardly  or  tlseoftheEus- 
outwardly,  so  that  no  condensation  or  rarefaction  shall  occur  tachian  tube- 
within  the  tympanic  cavity ;  for  such  rarefactions  and  condensations 
would  disturb  the  action  of  the  contracting  muscle,  and  make  it  yield  a 
false  estimate.  Besides  this,  the  Eustachian  tube,  as  has  long  been 
known,  affords  an  outlet  for  mucus. 

In  the  explanation  here  presented,  the  function  of  the  ossicles  is  rather 
for  the  purpose  of  tension  than  of  conduction,  though  it  is  Function  of  the 
not  denied  that  sounds  may  pass  readily  along  them.  They  ossicles- 
are  to  be  regarded  as  aiding  in  the  perfection  of  auditory  perceptions,  but 
yet  not  as  being  absolutely  essential  to  the  appreciation  of  sounds,  or 
even  of  their  finer  modifications.  Whatever  affects  the  facility  of  vibra- 
tion of  the  membrana  tympani,  such  as  its  thickening,  or  stiffening,  or 
unusual  dryness,  will  render  the  hearing  dull,  but  the  membrane  itself 
may  be  perforated,  or  even  undergo  extensive  lesions,  without  any  appar- 
ently corresponding  effect.  But  if  the  stapes  be  injured  or  be  removed, 
deafness  is  at  once  the  result. 

There  is  nothing  remarkable  in  the  precision  with  which  the  contrac- 
tions of  the  two  muscles  which  stretch  the  membrane  of  the  Precision  in  es- 
drum  are  made.  The  same  precision  is  illustrated  in  the  timatingthe 

,,  ,  ,  i  •  i       f  i  i          -i  rm  contraction  of 

case  of  the  muscles  which  adjust  the  vocal  cords.     The  state  the  auditory 
of  these  may  be  determined  to  the  -llr^00  part  of  an  inch.       ™scies. 

It  might  perhaps  be  inquired,  Why  should  not  the  function  of  determ- 
ining the  intensity  of  sounds,  as  well  as  their  wave  length,  be  imputed 
directly  to  the  auditory  nerve  ?  It  is  with  the  ear  as  with  the  eye,  the 
mechanism  for  determining  wave  length  can  only  act  with  uniformity 
when  the  agent  to  be  measured  is  reduced  to  a  standard  intensity.  A 


368  STRUCTURE  OF  THE  COCHLEA. 

bright  light  falling  upon  the  eye  brings  on  a  contraction  of  the  pupil. 
And  so  with  the  ear.  A  partial  deafening  must  be  established  to  adjust 
the  intensity  of  sound,  that  the  auditoly  nerve  may  act  under  standard 
circumstances.  The  primary  impression  therefore  made  upon  that  nerve 
by  the  loudness  of  sounds  is,  so  to  speak,  consumed  by  being  converted 
as  a  reflex  act  into  motion,  because  there  is  a  necessity  that  the  tensor 
and  stapedius  should  move,  and  reflex  acts  do  not  affect  the  mind,  but 
it  instantly  perceives  the  condition  of  contraction  of  those  muscles,  and 
so  estimates  the  intensity  of  the  sound. 

2d.  On  the  measurement  of  wave  length,  or  time  of  vibration  of  sounds. 
Structure  of  the  cochlea  and  its  functions. 

The  structure  of  the  cochlea  is  so  significant  that  its  true  function 
Structure  of  has  been  long  ago  more  or  less  distinctly  recognized.  Thus 
the  cochlea,  p^  Young  speaks  of  it  as  a  micrometer  of  sound.  Many 
physiologists  regard  it  as  determining  the  flote  or  pitch.  Any  one  who 
remarks  the  gradually  decreasing  width  of  its  spiral  lamina,  and  the 
manner  in  which  the  ultimate  filaments  of  the  auditory  nerve  are  spread 
thereon,  becoming  shorter  and  shorter  as  they  ascend  the  scale — who  re- 
calls the  structure  of  the  harp,  or  gradually  shorter  strings  of  the  piano- 
forte, could  scarcely  fail  of  being  impressed  with  the  truth  of  this  conclu- 
sion. The  function  of  the  cochlea  is  the  determining  of  wave  length, 
that  is,  the  time  of  vibration  or  note  of  sounds. 

The  cochlea  has  been  described  as  resembling  a  snail's  shell  in  appear- 
ance. It  is  a  conical  tube,  wound  spirally,  and  making  two  and  a  half 
turns.  The  interior  of  this  conical  and  spirally- winding  tube  is  divided 
throughout  its  length  into  two  portions  by  means  of  a  transverse  parti- 
tion, which,  following  the  spiral  winding  of  the  tube,  has  had  the  name 
of  lamina  spiralis  bestowed  on  it.  The  two  partitions  produced  by  the 
intervention  of  this  lamina  are  called  scala  vestibuli  and 

The  two  scalce.  . 

scala  tympani.  At  the  top  or  point  of  the  helix  the  two 
scalas  communicate  through  a  little  hole,  from  the  cessation  of  the  lamina 
spiralis.  To  this  opening  or  deficiency  the  name  of  helicotrema  is  given. 
Considering  the  two  scalse  as  separate  tubes,  their  mouths  open  differ- 
ently ;  the  scala  vestibuli  opens  into  the  vestibule  of  the  labyrinth,  and 
we  may  therefore  regard  the  membrane  of  the  fenestra  ovalis  as  being 
virtually  its  boundary  or  closure,  but  the  mouth  of  the  scala  tympani  is 
against  the  fenestra  rotunda,  and  is  closed  by  the  membrane  of  that  aper- 
ture. As  their  names  therefore  indicate,  the  scala  vestibuli  opens  into 
the  vestibule,  and  the  scala  tympani  into  the  tympanum. 

Passing  directly  through  the  body  of  the  cochlea,  and  being,  as  it 
introduction  were» tne  core  upon  which  that  structure  is  built,  is  a  bony 
of  the  auditory  cone,  called  the  modiolus.  Indeed,  the  bony  part  of  the 

transverse  plate  which  separates  the  tube  of  the  cochlea  into 


THE   SPIRAL  LAMINA. 


369 


Fig.  186. 


Interior  of  the  cochlea. 


Fig.  1ST. 


Section  of  the  cochlea. 


its  two  scalar,  might  be  regarded  as  a  spiral  process  of  the  modiolus. 
Through  the  modiolus  and  its  spiral  process,  or  lamina  spiralis,  the  au- 
ditory nerve  gains  access,  through  suitable  channels,  to  the  interior  of 
the  scalas. 

Fig.  186,  interior  of  the  cochlea,  rendered 
visible  by  the  removal  of  half  of  the  outer  wall: 

a,  a,  lamina  spiralis,  turning  by  its  inner  edge, 

b,  around  the  axis  of  the  cochlea ;  <?,  infundib- 
ulum ;  d,  aperture  of  communication  between 
two  scalaB;   e,  e,  section  of  the  outer  wall; 
fi  f->  ft  inferior  or  tympanic  scala ;  <?,  g,  g^  su- 
perior or  vestibular  scala. 

Fig.  187,  section  of  the  cochlea  in  the  direc- 
tion of  its  axis :  #,  canals  of  the  axis,  or  of 
the  columella,  for  the  passage  of  the  vascular 
and  nervous  ramifications;  £,  infundibulum ; 
c,  base  of  the  modiolus,  or  columella ;  d,  d,  d, 
section  of  spiral  lamina  ;  6,  e,  6,  section  of  the 
outer  wall;  f,f,fi  inferior  scala;  <7,  <?,  superior 
scala. 

It  is  necessary  to  understand  the  structure  of  the  lamina  spiralis  more 
particularly.  As  we  have  said,  it  divides  the  helical  tube  into  The  spiral 
the  two  scake  by  extending  transversely  across  it.  Its  bony  por-  lamina. 
tion  does  not,  however,  extend  more  than  about  one  third  of  the  distance, 
the  rest  of  it  being  made  up  in  part  of  a  delicate  membranous  portion, 
and  completed  by  a  muscular  structure ;  so  that,  if  we  consider  the  lam- 
ina spiralis  at  any  point,  the  region  of  it  near  the  modiolus  is  bone,  the 
intermediate  portion  membranous,  and  the  residual  is  muscular.  Or, 
considering  the  lamina  spiralis  in  the  aggregate,  we  might  say  that  it 
consists  of  a  helix  of  bone,  membrane,  and  muscle.  To  the  muscle  the 
name  of  the  cochlearis  is  given.  Its  obvious  function  is  to  tighten  the 
membranous  region.  Moreover,  considered  thus  in  the  aggregate,  the 
lamina  spiralis  is  a  triangular  plate  wound  round  upon  a  central  conical 
core,  and  which,  therefore,  is  broadest  at  the  base  of  the  cochlea,  and 
gradually  tapers  off  toward  the  apex.  It  is  to  be  understood  that  the 
cochlea,  like  all  other  portions  of  the  labyrinth,  is  filled  with  water. 

Upon  the  spiral  lamina,  issuing  forth  through  its  bony  portion,  are 
placed  the  ultimate  filaments  of  the  auditory  nerve.  These,  having  cast 
off  their  white  substancer  come  into  relation  with  elongated  vesicles, 
and  are  thus  distributed  upon  the  membranous  portion,  the  membrane 
being  kept  uniformly  tense  by  the  action  of  the  cochlearis  muscle. 

Fig.  188,  p..  370,  section  of  the  cochlea  through  its  axis,  magnified  four 
diameters,  and  showing  the  cochlear  branch  of  the  auditory  nerve,  ac- 

AA 


370 


STRUCTURE    OF   THE    COCHLEA. 


Fig.  1S8. 


Magnified  section  of  cochlea. 


companied  "by  some  vascular  ramifica- 
tions across  the  conduits  of  the  colu- 
mella  to  the  spiral  lamina. 

Fig.  189,  section  of  the  cochlea,  mag- 
nified six  diameters,  to  show  the  dis- 
tribution of  the  cochlear  branch  of  the 
auditory  nerve  from  its  perforation  of 
the  columella  to  its  termination  on  the 
spiral  lamina. 

Figs.  190,  191,  showing  the  middle 
and  internal  ear  by  a  section  of  the 
superior  face  of  the  petrous  bone,  and 
principally  the  entire  distribution  of 
the  auditory  nerve :  .«,  #,  hammer, 
holding,  &,  &,  &,  its  internal  muscle ;  c, 


Fig.  189. 


Fig.  190. 


Distribution  of  cochlear  nerve. 

c,  c,  its  anterior  muscle  ;  and,  d,  its 
external  muscle ;  e,  e,  anvil ;  /",  len- 
ticular bone ;  g,  stirrup ;  h,  muscle 
thereof;  i,  chorda  tympani;  j,  fa- 
cial nerve,  receiving,  &,  great  su- 

Ftn.  1C1. 


The  ossicles  and  their  muscles. 


General  distribution  of  auditory  nerve. 

perficial  petrosal ;  Z,  cochlea  ;  m,  auditory  nerve;  n,  its  cochlear  branch ; 
and,  o,  its  vestibular  branch,  furnishing,^,  branch  of  posterior  vertical 


FUNCTION  OF  THE   COCHLEA.  371 

canal ;  q,  branch  of  sacculus  ;  71,  branch  of  utricle ;  s,  branch  of  horizon- 
tal canal ;  t,  t,  branch  of  superior  vertical  canal. 

We  proceed  now  to  the  consideration  of  the  functions  of  the  cochlea. 

The  principles  of  acoustics  would  lead  us  to  infer  that  sounds  entering 
the  cochlea  throw  into  vibration  its  spiral  lamina,  an  inference  Functions  of 
which  is  supported  by  anatomical  considerations  in  regard  to  the  cochlea, 
the  position  and  function  of  the  cochlearis  muscle  in  keeping  the  mem- 
branous portion  of  the  lamina  at  a  due  degree  of  tension.  We  should 
also  infer  that  each  external  sound  does  not  throw  the  lamina  into  vi- 
bration throughout  its  whole  length,  but  only  on  a  special  and  corre- 
sponding point,  and  thereby  affects  solely  the  filament  of  the  auditory 
nerve  in  connection  with  that  point ;  that  sounds  which  are  low  will  act 
upon  the  broader  portions  of  the  membrane,  near  the  mouth  of  the  coch- 
lea, and  those  which  are  high,  the  narrower  portions  near  the  apex.  In 
this  respect,  therefore,  the  function  of  hearing  should  have  two  limits, 
one  for  low  and  the  other  for  high  notes,  as  experience  proves  to  us  is 
actually  the  case ;  but  possibly  the  scale  is,  so  to  speak,  enlarged  through 
the  various  degrees  of  tenseness  which  may  be  given  by  the  contractions 
of  the  cochlearis  muscle.  A  general  idea  of  the  nature  of  this  limited 
vibration  may  be  obtained  by  recalling  the  effect  which  is  Physical  iiius- 
produced  when  one  musical  instrument  is  played  in  the  vi-  ^J^"^^^16 
cinity  of  another,  as  when,  for  example,  a  flute  is  played  cochlea. 
near  to  a  piano-forte,  the  strings  of  the  latter  are  thrown  into  sympathetic 
vibration,  and  the  piano  emits  a  note  answering  to  each  note  of  the  flute. 
All  the  strings  are  not  thrown  into  vibration  at  once,  but  for  each  note 
of  the  flute  that  string  of  the  piano  vibrates,  the  length  and  tension  of 
which  are  duly  adjusted.  The  same  thing,  again,  may  be  seen  when 
musical  sounds  are  originated  near  a  stretched  membrane,  the  surface  of 
which  has  been  dusted  over  with  grains  of  dry  sand.  The  whole  sheet 
of  the  membrane  is  not  cast  into  vibration  at  once,  but  some  parts  move 
and  some  remain  at  rest,  and  so  the  sand-grains  dance  up  and  down  on 
the  vibrating  parts,  and  soon,  being  cast  therefrom,  accumulate  on  the 
parts  that  are  still,  and  mark  out  what  are  termed  nodal  lines.  These 
nodal  lines,  or  places  which  are  motionless,  are  frequently  of  remarkable 
complexity  and  symmetry,  as  may  be  seen  from  the  figures  of  them  given 
in  any  of  the  books  on  natural  philosophy.  m 

It  is  immaterial  in  what  manner  the  sound  has  reached  the  cochlea, 
whether  through  the  auditory  canal  or  through  the  bones  of   Course  of 
the  skull  generally;  the  effect,  as  far  as  the  spiral  lamina  is  sounds  to  the 
concerned,  will  be  the  same  in  both  cases.     That  sounds  can  cochlea- 
efficiently  reach  the  auditory  nerve,  and  produce  thereupon  their  proper 
effect,  without  ever  having  passed  through  the  auditory  canal  or  the  drum, 
is  manifested  by  a  great  many  familiar  facts.     We  still  continue  to  hear 


372  INTERFERENCE   OF   SOUNDS. 

distinctly,  though  not  so  plainly,  when  the  external  canal  is  closed  by 
some  obstruction — nay,  even  when  the  sound-giving  object,  as  a  watch, 
is  put  into  the  mouth.  So  it  would  appear  that  the  function  of  the  coch- 
lea is,  in  a  certain  sense,  independent  of  the  drum,  though  we  have  to 
admit  that,  for  the  precision  and  perfection  of  hearing,  the  latter  is  nec- 
essary. 

In  the  view  here  presented,  I  consider  that  each  external  musical  note 
The  cochlea  causes  a  special  portion  of  the  spiral  lamina  to  vibrate,  and 
HEKfiL  that  the  particular  nerve  fibril  supplying  that  portion  is  af- 
tion  of  sounds,  fected  thereby,  and  thus  a  distinct  sensation  is  communi- 
cated to  the  brain,  the  nerve  fibrils  to  the  right  and  left  of  the  one  af- 
fected lying  at  rest.  It  may  probably  be  that  the  denticulate  structure 
-described  by  Drs.  Todd  and  Bowman  has  for  its  duty  the  more  perfect 
production  of  this  isolated  effect,  or  that  the  teeth  thereof  act  like  the 
dampers  of  a  musical  instrument,  and  restrain  the  vibration.  Notes  the 
wave  length  of  which  is  great,  or,  what  is  the  same  thing,  the  times  of 
the  vibrations  of  which  are  long,  affect  those  portions  of  the  spiral  lamina 
which  are  broad  and  near  to  the  base  of  the  cochlea,  but  notes  whose  wave 
lengths  are  short,  and  times  of  vibration  correspondingly  brief,  affect 
those  portions  near  to  the  apex.  But  probably  the  scale  is  changed,  as 
before  said,  by  the  tension  of  the  cochlearis  muscle,  and  thus  the  same 
part  of  the  lamina  can  take  charge  of  a  range  of  many  octaves. 

It  may  be  inquired  how  it  is  that  a  sound  passing  through  the  audi- 
tory  canal,  the  bones  of  the  tympanum,  the  membrane  of  the 
an  interference  fenestra  ovalis,  and  thus  affecting  its  destined  portion  of  the 
mechanism.  laminaj  does  not  give  rise  to  an  idea  in  the  mind  of  repeti- 
tion or  reverberation  by  moving  back  and  forth  through  the  two  scala3, 
and  affecting  its  proper  nerve  fibril  at  each  passage.  Is  there  not  a  ne- 
cessity for  the  existence  of  some  mechanism  of  interference  which  shall 
destroy  the  wave  after  it  has  once  done  its  work  ?  Admitting  the  force 
of  such  inquiries,  we  can  not  avoid  being  impressed  with  the  fact  'that 
the  two  scala3  into  which  the  cochlear  tube  is  divided  present  all  the  as- 
pects of  a  mechanism  constructed  for  the  discharge  of  such  a  duty.  For 
interference  to  take  place  among  undulations  of  any  kind,  waves  upon 
water,  sounds  in  the  air,  or  the  ethereal  undulations  which  constitute  light, 
the  essential  condition  is  that  they  shall  run  through  paths  of  unequal 
length,  the  inequality  being  one  of  a  series  of  numbers.  They  must  also 
be  brought,  for  a  full  practical  effect,  to  their  common  point  of  encounter 
under  a  very  acute  angle,  and  these  conditions  are  represented  in  the 
scala  vestibuli  and  the  scala  tympani,  which  are  of  unequal  length,  placed 
at  such  an  acute  angle  to  one  another  that  they  might  almost  be  said  to 
be  parallel,  occupied  by  a  fluid  of  the  same  density,  and  through  both  at 
the  same  moment  are  passing  the  undulations  which  constitute  the  same 


FUNCTION  OF  THE  COCHLEA.  373 

sound,  one  having  been  communicated  by  the  fenestra  ovalis,  the  other 
through  the  fenestra  rotunda,  their  common  point  of  convergence,  and 
perhaps  of  mutual  destruction,  being  at  the  helicotrema,  the  aperture  at 
the  apex  through  which  they  intercommunicate.  Nor  can  we  fail  to  be 
struck  by  the  circumstance,  if  this  explanation  of  the  function  of  the 
scalse  be  correct,  in  what  an  admirable  manner  the  whole  in-  .  d.  tment  of 
strument  is  provided  with  self-adjusting  power,  since,  when  the  length  of 
the  stirrup  forces  in  the  membrane  of  the  fenestra  ovalis,  the  t] 
pressure  which  is  communicated  through  the  water  pushes  out  the  mem- 
brane of  the  fenestra  rotunda,  and  thereby  the  relative  length  of  the  two 
scalas  has  changed,  the  one  having  become  longer  by  as  much  as  the 
other  has  become  shorter,  an  adjustment  necessary  to  bring  about  total 
interference  at  the  helicotrema.  And  we  might  add  that. such  a  con- 
struction is  all  the  more  interesting,  for,  since  it  is  the  intensity  of  the 
waves  that  is  to  be  destroyed,  reliance  is  had  upon  the  intensity  instru- 
ment, the  drum,  to  produce  that  effect,  and  it  is  done  by  the  contractions 
of  the  tensor  tympani  and  stapedius  muscles.  Perhaps  the  perfect  ac- 
complishment of  this  interference  is  the  standard,  to  which  allusion  has 
been  made  before,  by  which  the  mind  judges  of  the  power  which  has  been 
put  forth  by  those  muscles,  and  thereby  of  the  intensity  of  the  sound. 

From  the  comparative  anatomy  of  the  cochlea  and  the  character  of  the 
vocal  organs,  JVI.  Duges  formerly  came  to  the  conclusion  that  Com  arative 
the  cochlea  has  for  its  function  the  determining  of  the  pitch  anatomy  of  the 
of  sounds.     In  man,  whose  vocal  powers  are  most  varied,  it  Cl 
exists  in  the  highest  perfection ;  in  birds,  whose  vocal  powers  are  more 
restricted,  it  is  reduced  to  a  short  and  slightly  curved  tube,  but  still  di- 
vided by  a  longitudinal  septum ;  in  reptiles,  it  exists  only  in  a  rudiment- 
ary state. 

The  necessary  existence  in  the  ear  of  some  mechanism  for  the  purpose 
of  preventing  reverberation  or  repercussion  has  long  been  recognized 
both  by  writers  on  acoustics  and  by  physiologists.  Thus  an  explana- 
tion of  the  functions  of  the  semicircular  canals  and  of  the  cochlea  upon 
this  principle  is  given  by  Dr.  Koget,  in  his  Bridgewater  Treatise ;  and, 
in  like  manner,  Professor  Jackson,  of  Philadelphia,  has  for  several  years 
taught  a  similar  doctrine  in  his  lectures.  Since  1840, 1  have  in  my  pub- 
lic lectures  presented  the  explanation  given  in  the  preceding  paragraphs. 
It  differs  essentially  from  that  of  my  friend,  Professor  Jackson  (of  which 
a  brief  statement  may  be  found  in  Dr.  Smith's  edition  of  Carpenter's 
Physiology,  Philadelphia,  1855),  in  this,  that  it  limits  the  accomplish- 
ment of  interference  to  the  cochlea.  The  view  which  I  entertain  respect- 
ing the  function  of  the  semicircular  canals  will  be  immediately  set  forth  : 
it  does  not  appear  to  me  that  they  are  in  any  way  connected  with  the  in- 
terference mechanism. 


374 


STRUCTURE   OF   THE   SEMICIRCULAR   CANALS. 


3d.  On  the  determination  of  the  quality  of  sounds,  the  structure  of  the 
semicircular  canals,  and  their  function. 

The  semicircular  canals  are  cylindroid  tubes,  developed,  as  it  were, 
ureofthe  ^rom  the  vestibule,  and  of  a  figure  which  has  suggested  their 
semicircular  name.  They  are  three  in  number,  and  placed  at  right  angles 
to  one  another :  two  of  them  are  vertical,  the  third  horizon- 
tal ;  they  all  open  into  the  vestibule,  the  adjacent  branches  of  two  of 
them  coalescing  first.  On  one  of  the  branches  of  each  of  them  there  is 
a  dilatation  just  before  it  joins  the  vestibule ;  to  this  dilatation  the  des- 
ignation of  ampulla  is  given.  The  vestibule  of  the  labyrinth  may  there- 
fore be  regarded  as  the  common  mouth  of  the  semicircular  canals,  and  of 
the  scala  vestibuli  of  the  cochlea ;  or,  considering  its  order  of  develop- 
ment, the  vestibule  may  be  regarded  as  the  essential  portion  of  the  lab- 
yrinth, and  the  semicircular  canals  and  cochlea  appendices  that  have 
branched  forth  from  it. 

The  vestibule  and  semicircular  canals  are  lined  with  a  membrane 
which,  of  course,  copies  their  shape,  yet  it  is  not  in  contact  with  their 
bony  walls,  but  is  parted  therefrom  by  a  stratum  of  water,  to  which,  as 
has  been  said,  the  name  of  perilymph  is  given ;  their  interior  is  also 
filled  with  a  liquid — the  endolymph,  it  is  called.  The  bony  structure  is 
called  the  bony  labyrinth ;  this  structure  is  the  membranous  labyrinth. 
A  portion  of  the  auditory  nerve  divides  into  three  main  branches,  which 
present  themselves  for  the  supply  of  the  ampullae :  the  brush-like  termi- 
nations of  these  are  accommodated  with  an  otolith. 


ILLUSTRATIONS   OF   LABYRINTH   OF   LEFT   SIDE. 

EXTERNAL,  OB   TYMPANIC   FACE   OF   LABYRINTH. 


Fig.  192. 


Tympanic  face  of  the  labyrinth. 


Fig.  192  :  #,  external  wall  of  vestibule,  on  which 
is  seen,  &,  fenestra  ovalis  ;  £,  fenestra  rotunda, 
and,  d,  tract  of  the  facial  nerve  ;  0,  superior  semi- 
circular  canal  ;  /*,  posterior  semicircular  canal  ;  <?, 
horizontal  semicircular  canal  ;  i,  i,  i,  wall  of  coch- 
lea ;  j,  aqueduct  of  cochlea  ;  &,  portion  of  petrous 


Fig.  193. 


INTERNAL,  OR   CRANIAL  FACE   OF   LABYRINTH. 

Fig.  193 :  a,  internal  wall  of  vestibule ;  b,  aque- 
duct of  vestibule ;  c,  base  of  cochlea  ;  d ,  aqueduct 
of  cochlea ;  e,  /*,  conduit,  at  the  bottom  of  which 
are  several  holes  for  the  passage  of  facia)  and  au- 
ditory nerves;  g,  superior  semicircular  canal;  A, 
cranial  face  of  the  labyrinth,  posterior  semicircular  canal ;  i,  horizontal  semicir- 
cular canal. 


FUNCTION    OF   THE   SEMICIRCULAR   CANALS.  375 

INTERIOR   OF   LABYRINTH,    SEEN    ON   ITS    EXTERNAL    OR    TYMPANIC    FACE. 

Fig.  ic4.  Fig.  194 :  #,  vestibule,  into  which  open  the  semi- 

circular canals  by  five  orifices,  and  the  vestibular 
scala  of  the  cochlea ;  b,  b,  section  of  the  wall  of  the 
cochlea  ;  <?,  c,  bony  portion  of  spiral  lamina,  dividing 
the  conoid  cavity  of  the  cochlea  into  scala  vestibuli 
interior  of  labyrinth.  and  scala  tympani ;  d,  orifice  at  summit  of  cochlea. 

INTERIOR   OF   LABYRINTH,   SEEN   ON   ITS   INTERNAL   OR   CRANIAL  FACE. 

Fig.  ic5.  Fig.  195 :  #,  vestibular  cavity,  into  which  open  the 

cavities  of  the  semicircular  canals  and  the  cochlear  cav- 
ity ;  b,  bottom  of  internal  auditory  canal,  answering  to 
base  of  cochlea,  'and  partly  to  internal  wall  of  vestibule ; 
,  simple  foramen  for  facial  nerve ;  d,  many  openings 
interior  of  labyrinth.     for  auditory  nerve. 

The  explanation  usually  given  of  the  function  of  the  semicircular  ca- 
nals is,  that  they  serve  to  determine  the  direction  of  sounds,   Criticism  on 
an  idea  which  has  arisen  from  their  remarkable  rectangular  the  expiana- 
position.     However,  this  is  accomplished  in  almost  all  cases  ^"^life 
by  directing  the  external  canal  toward  the  point  from  which  function  of  the 
the  sound  is  coming,  and  judging  of  its  place  by  the  varia- 
tions of  its  intensity.     Animals  commonly  direct  the  external  ear  toward 
the  sounding  point,  guided  doubtless  in  the  same  way.      Some  physiolo- 
gists have  restricted  the  use  of  the  semicircular  canals  to  the  collection 
of  those  sounds  which  strike  upon  the  skull,  but,  besides  the  preceding 
considerations,  there  are  others  derived  from  comparative  anatomy  which 
seem  to  indicate  that  this  can  scarcely  be  their  duty. 

The  intensity  of  sounds  is  judged  of  by  the  tympanum ;  their  pitch 
or  wave  length  is  determined  by  the  cochlea,  and  therefore  They  are  for 
there  arises  a  strong  presumption  that  the  semicircular  ca-  qSu4a™tatl"f  tt 
nals  must  have  the  function  of  distinguishing  the  third  char-  sounds. 
acteristic  of  sounds,  that  is,  their  quality ;  since,  if  this  be  not  the  case, 
there  seems  to  be  no  other  portion  of  the  auditory  mechanism  to  which 
that  office  could  be  assigned. 

The  suspicion  which  we  are  thus  led  to  entertain,  that  the  semicircu- 
lar canals  are  for  appreciating  the  quality  of  sounds,  is  strengthened  in 
no  common  degree  by  facts  of  comparative  physiology.  Unfortunately, 
we  know  so  little  of  the  mechanical  peculiarity  on  which  distinctions  of 
quality  depend,  that  we  are  wholly  unable  to  trace  out  the  structural  con- 
ditions of  an  organ  which  should  be  calculated  for  seizing  on  them.  We 
know  that  the  quality  of  a  note  emitted  by  a  violin  is  different  from  that 
emitted  by  a  flute,  though  the  intensity  and  pitch  may  be  the  same,  but 


376  COMPARATIVE  ANATOMY   OF   THE   EAR. 

we  can  not  tell  why.  In  the  case  before  us,  we  therefore  can  expect  no 
assistance  in  the  way  of  arguments  from  mechanical  philosophy,  and  are 
limited  to  the  use  of  those  which  may  "be  drawn  from  comparative  anat- 
omy and  physiology. 

Examining,  therefore,  what  appears  to  be  the  primitive  plan  of  the  con- 
Illustration  of  struction  of  this  mechanism,  we  find  it  to  consist  of  a  nerve 
thisexpiana-  fibril  .in  connection  with  an  otolith,  or  little  stony  body. 

tion  from  com-    ^      .  j  •         •      i     i    i  •          i  r  • 

parative  anat-  Such  a  construction,  included  in  a  bag  01  water,  constitutes, 
°my-  in  point  of  fact,  the  organ  of  "hearing  of  some  of  the  lower 

tribes,  as  the  gasteropodous  molluscs.  These  animals  can  have  no  per- 
ception of  the  pitch  of  sounds  or  musical  notes,  and  only  an  imperfect  one 
of  intensities.  But  what  they  do  distinguish  is  one  noise  from  another. 
Now  the  idea  conveyed  to  the  mind  by  difference  of  noises  is  precisely 
the  distinction  that  we  are  dwelling  on,  that  of  quality. 

If,  instead  of  restricting  our  examination  to  the  semicircular  canals,  we 
General  view  exten(^  &  *°  tne  whole  organ  of  hearing,  and  consider  to- 
of  the  auditory  gether,  in  the  case  of  each  animal  tribe,  its  requirements,  and 
sm'  the  manner  in  which  those  requirements  are  satisfied,  we 
shall  meet  with  a  surprising  confirmation  of  the  preceding  views.  The 
lowest  requirement  we  can  conceive  of  is  the  appreciating  of  noises ;  an 
advance  upon  this  is  the  determination  of  their  direction ;  a  higher  ad- 
vance, the  determination  of  their  intensity ;  and  a  still  higher,  the  rec- 
ognition of  those  combinations  of  impulses  which  constitute  a  musical 
sound.  For  each  of  these  successive  requirements  the  auditory  mech- 
anism must  necessarily  become  more  complex ;  and  thus  it  first  ap- 
pears, as  we  have  just  stated,  as  a  sac  of  water,  containing  a  stony  grain 
or  otolith  imbedded  in  the  cesophageal  collar.  A  noise  agitates  the  oto- 
Com  arative  ^^'  an<^  ^7  its  movement  the  perception  of  a  sound  ensues, 
anatomy  of  the  In  cephalopodous  molluscs  the  auditory  sac  is  detached,  and 
the  intercommunicating  thread  represents  the  rudiment  of 
what,  in  the  higher  grade  of  development,  will  be  the  auditory  nerve. 
With  another  advance  the  sac  is  lodged  in  a  cartilaginous  cavity.  Thus, 
in  the  cuttle-fish,  a  simple  cartilaginous  vestibule  exists,  having  within 
it  a  membranous  bag  or  auditory  capsule,  filled  with  fluid,  and  upon  the 
capsule  the  filaments  of  the  auditory  nerve  are  spread.  An  otolith  or 
ear-stone  is  placed  within,  and  this  constitutes  the  entire  apparatus,  while 
yet  there  is  no  vibrating  membrane  and  no  fenestral  aperture. 

Even  in  still  higher  conditions  the  purely  mechanical  character  of  the 
structure  is  manifest,  and  so,  in  some  of  those  in  which  the  sac  opens  ex- 
teriorly, grains  of  sand,  that  have  been  introduced  by  chance  from  without, 
rest  on  the  hair  like  filaments  which  the  auditory  sac  contains,  each  fila- 
ment apparently  including  a  nerve  fibril.  In  a  still  higher  condition  of 
advance,  as,  for  example,  in  the  lobster,  a  portion  of  the  shelly  wall  which 


COMPARATIVE  ANATOMY  OF  THE  EAR.  377 

forms  the  boundary  of  the  auditory  cavity  is  unconsolidated,  and  a  mem- 
brane which  stretches  over  the  otherwise  vacant  space  presents  the  first 
rudiment  of  the  fenestra  ovalis.  With  the  exception  of  the  amphioxus, 
all  vertebrated  animals  have  a  special  organ  of  hearing,  which,  in  suc- 
cessive tribes,  presents  an  interesting  increase  of  complexity,  beginning  in 
the  cyclostomes  with  a  sac  in  the  cranial  cartilages  filled  with  water, 
nerve  fibrils  distributed  on  its  walls,  and  an  otolith  included,  but  no  ex- 
ternal communicating  aperture.  From  this,  in  succession,  the  various 
portions  which  are  to  be  developed  in  perfection  in  the  higher  races  grad- 
ually appear:  the  myxine  has  one  semicircular  canal  arising  from  the 
vestibule,  the  lamprey  has  two,  the  higher  forms  have  three.  As  the  case 
may  be,  a  portion  of  the  cartilage  or  bony  parietes  is  deficient,  and,  again, 
the  fenestra  ovalis  is  the  result.  Though  in  the  osseous  fishes  there  is 
neither  tympanum  or  cochlea,  in  some  few  the  rudiments  of  the  former 
begin  to  exist.  The  naked  amphibia  have  no  cochlea,  and  only  one  fe- 
nestra, answering  to  the  ovalis :  to  this  is  fitted  a  stapes ;  but  in  lizards 
and  scaly  serpents  there  is  a  general  advance,  these  having  a  conical 
cochlea.  As  we  pass  through  them  the  plan  is  earned  out ;  the  tympan- 
ic cavity  and  its  chain  of  bones,  the  Eustachian  tube,  and  cochlea  ap- 
pear; and  with  the  rudiment  of  the  cochlea  there  is  presented  in  the  tym- 
panic cavity  a  second  aperture,  answering  to  the  fenestra  rotunda.  In 
birds  the  structure  offers  a  continued  improvement,  commencing  on  a 
plan  analogous  to  that  of  the  scaly  amphibia,  but  exhibiting  a  speedy 
development. .  The  membrana  tympani  is  composed  of  several  layers ; 
the  cavity  of  the  drum  communicates  with  cells  in  the  cranial  bones,  the 
analogues  of  the  mastoid  cells  ;  a  bony  Eustachian  tube  crosses  to  meet 
its  fellow  of  the  opposite  side,  and  open  in  a  common  aperture.  The  os- 
sicles consist  of  a  malleus,  a  staff-shaped  intermediate  bone,  and  a  flat 
stapes,  resting  on  the  fenestra  ovalis.  As  if  to  show  a  tendency  to  the 
form  it  is  eventually  to  assume,  this  bone  sometimes  presents  a  forked 
appearance,  the  preparation  for  a  stirrup  shape.  As  regards  this  bone, 
birds  and  mammals  may  be  said  to  overlap,  for  in  its  more  developed 
condition  in  birds  it  bifurcates,  but  in  the  lower  mammals,  as  the  kanga- 
roo, it  is  still  cylindric.  In  birds  of  prey  the  semicircular  canals  are 
large,  the  cochlea  fairly  developed,  though  as  a  straight  or  slightly-curved 
tube,  containing  its  scake  and  vibrating  lamina :  the  vestibule  has  ear- 
stones.  Through  the  monotremata  this  condition  of  construction  is  con- 
tinued into  the  perfect  mammals  :  all  the  aerial  tribes  have  external  ears, 
and  full  development  is  reached  in  the  auditory  mechanism  of  man. 

Now  if  we  collate  the  facts  here  presented  with  the  requirement  of  the 
condition  of  life  which  each  of  these  successive  races  seems  to  demand,  we 
shall  find  that  the  remark  heretofore  made,  that  the  semicircular  canals 
are  for  the  recognition  of  the  qualities  of  sound,  is  strikingly  borne  out, 


378  DEVELOPMENT   OP   THE   EAR. 

though,  from  our  ignorance  of  what  it  is  in  which  quality  consists,  we  are 
wholly  unable  to  offer  an  explanation  of  the  precise  mode  of  action  of 
that  part  of  the  auditory  mechanism. 

We  are  so  prone  to  extend  our  ideas  of  our  own  perceptions  to  the 
Partial  deaf  case  °^  otner  animals  that  it  may  not  here  be  unprofitable  to 
ness  of  inferior  offer  a  remark  which  may  serve  to  correct  such  views.  To 
many  of  the  sounds  with  which  we  are  familiar,  birds  and  oth- 
er lower  tribes  are  totally  deaf;  they  can  not  appreciate,  except  within  a 
narrow  range,  the  notes  of  music,  and,  indeed,  to  all  those  in  which  there 
is  no  cochlea  such  notes  are  inaudible.  -  In  the  lower  grades  nothing  more 
than  a  noise  can  be  detected,  and  that  doubtless  in  a  very  indefinite  way. 
We  can  therefore  understand  how,  through  imperfection  of  construction, 
they  are  cut  off  from  the  perception  of  an  infinite  number  of  occurrences 
which  are  obvious  enough  to  us.  Even  among  our  domestic  animals,  to 
which  we  so  often  speak  or  sing  in  the  way  we  do  to  one  another,  the  in- 
tellectual obtuseness  which  we  think  we  recognize  doubtless  originates 
in  an  incapacity  to  receive  those  expressions,  because  of  faulty  structural 
condition. 

In  closing  these  remarks  on  the  sense  of  hearing,  it  is  necessary  to 
,    direct  attention  to  the  order  of  development  of  the  organ  in 

Order  of  devel-     ,.,,,,,,,  .r  & 

opment  of  the  the  individual  of  the  human  species,  as  we  have  done  in  the 
case  of  the  successive  tribes  of  animals  ;  and  here  it  may  be 
affirmed  that  the  ear  of  man  passes  in  a  transient  succession  through  all 
these  permanent  animal  forms.  It  originates  at  first  from  a  budding 
forth  of  the  vesicle  of  the  medulla  oblongata,  the  issuing  cell  becoming 
by  degrees  pear-shaped,  and  connected  with  the  parent  cavity  by  a  thread 
or  stalk.  The  pear-shaped  cavity  is  the  rudiment  of  what  is  eventually 
to  be  the  vestibule  ;  the  pedicle  will  become  the  auditory  nerve.  Even 
at  this  early  period  the  cavity  contains  an  otolith.  By  degrees  there 
arises  from  the  folding  in  of  the  walls  of  the  vestibule  the  curved  forms 
that  are  to  become  the  semicircular  canals,  and,  at  a  period  a  little  later, 
in  an  analogous  way,  the  cochlea.  At  one  stage  of  this  development  the 
membranous  labyrinth  presents  an  almost  identical  aspect  with  that  of 
the  retina  at  the  time,  both  being  composed  of  a  fibrous  network  inter- 
spersed with  granules  and  nucleated  cells,  the  shadowing  forth  of  the 
parallelism  of  construction  which  may  be  traced  in  the  two  organs  when 
they  have  reached  their  utmost  development,  the  one  for  the  cognizance 
of  normal  and  the  other  for  transverse  vibrations. 

And  so  it  appears  that,  as  respects  the  organ  of  hearing,  its  order  of 
illustration  of  development  in  the  individual  is  identically  the  same  as  its 
the  imperfec-  order  of  development  in  successive  tribes  taken  in  the  ag- 

tionofthedoc-  _          r    _  _    . 

trine  of  means  gregate.  In  the  latter  case,  we  constantly  regard  its  con- 
and  ends.  dition  of  construction  as  arising  from  a  purposed  adaptation 


VISION.  379 

to  the  wants  of  the  animal.  We  consider  it  as  affording  a  series  of  il- 
lustrative instances  of  the  use  of  means  for  the  production  of  definite 
ends,  and  therefore  as  exhibiting  the  evidences  of  design ;  but  what  are 
we  to  make  of  the  other,  the  parallel,  the  individual  case,  in  which,  in 
succession,  the  organ  presents  each  one  of  these  particular  forms,  and  in 
which  not  one  is  ever  used,  save  only  the  most  complete,  the  last? 
There  would  seem  here  to  be  little  of  adaptation,  little  of  means  to  an 
end,  nothing  of  design.  But  does  not  this  prove  to  us  (and  the  other 
organs  of  sense  will  furnish  a  similar  argument)  that  the  development  of 
the  various  animal  tribes,  and  of  each  individual  of  those  tribes,  takes 
place  under  the  operation  of  a  far-reaching  and  common  law,  and  that  the 
particular  condition  which  any  species  presents,  or  even  any  individual 
at  some  special  period  of  his  existence,  is  a  manifestation  of  the  degree 
or  extent  to  which  that  law  has  been  carried  out  ? 


CHAPTER  XX. 

OF  VISION. 

Analogy  between  Sound  and  Light. —  Comparative  Anatomy  of  Vision. — Perception  of  Warmth. 
— Structure  of  Ocelli. —  Use  of  Lenses. — Physical  Principle  of  the  Organ  of  Vision. 

Description  of  the  Human  Eye. —  Optical  Action  of  its  Parts. — Spherical  and  Chromatic  Aberra- 
tion:— Receiving  Screen  of  the  Eye  is  the  black  Pigment. — Long  and  short  Sight,  and  their 
Correction. — Limits  of  Vision  are  included  in  one  Octave. — Limit  in  estimating  the  Brightness 
of  Light. 

Nervous  Mechanism  of  the  Eye :  its  Structure  and  Functions. — Manner  of  Perception  by  the 
Retina. —  The  black  Pigment  absorbs  the  Rays. — Single  and  double  Vision. — Duration  of  Im- 
pressions.—  Ocular  Spectra. — Erect  Vision. — Idea  of  the  Solidity  of  Bodies. — Hypothesis  of 
the  Action  of  the  Retina. 

Accessory  Apparatus  of  the  Eye. — The  Eyebroios. — Eyelids. — Lachrymal  Apparatus. — Muscles 
of  the  Ball. 

THE  physical  difference  between  waves  of  sound  and  waves  of  light 
has  been  already  stated  to  consist  in  this,  that  the  vibrations  . 
which  give  rise  to  the  former  coincide  with  the  direction  in  tween  sound 
which  the  wave  passes,  but  those  of  the  latter  are  transverse.  and  llght' 
There  is,  however,  notwithstanding  this  difference,  a  general  analogy  be- 
tween the  structure  of  the  ear  and  that  of  the  eye,  and  provision  must 
be  made  in  the  case  of  the  organ  of  sight  for  determining  the  fundamental 
peculiarities  which  are  necessary  to  be  determined  in  the  case  of  the  or- 
gan of  sound ;  that  is  to  say,  intensity,  wave  length,  or  time  of  vibra- 
tion, and,  in  addition  thereto,  the  requirements  of  this  particular  prob- 
lem demand  that  means  should  be  included  for  ascertaining  with  exact- 
ness the  shape  of  objects  and  their  relative  positions. 


380  PERCEPTIONS   OF  WARMTH. 

Of  the  different  methods  which  we  might  follow  in  the  discussion  of 
Importance  of  the  mechanism  of  the  eye,  none,  perhaps,  is  more  satisfacto- 
the  compara-  Qr  jea(js  to  clearer  conclusions,  than  that  which  is  pre- 

tive  anatomy        J '  ' 

of  vision.  sented  by  comparative  anatomy.  It  is  just  as  difficult  to 
take  a  complicated  organ,  such  as  the  eye  of  man,  and  from  the  study 
of  it  to  deduce  the  significance  of  its  various  parts,  as  it  would  be  to  take 
a  complicated  human  contrivance  and  determine  from  it  the  properties  of 
its  mechanical  elements.  It  is  scarcely  from  the  watch  or  other  delicate 
machine  that  we  should  expect  to  make  plain  the  properties  of  the  lever 
or  the  wheel,  and  experience  shows  that  it  is  only  by  the  attentive  study 
of  the  cases  presented  by  comparative  physiology — those  experiments 
made  for  us  by  nature,  as  CUVIER  has  called  them — that  we  can  hope  to 
advance  to  the  perfect  solution  of  this  problem. 

Treating  the  subject,  therefore,  in  this  way,  we  observe  that,  in  the  an- 
Confused  er  *ma^  ser^es'  ^onS  Before  any  thing  like  a  distinct  organ  of  vis- 
ception  of  ion  can  be  detected,  there  is  yet  a  perception  of  light  and 
warmth.  darkness.  The  hydra,  a  fresh-water  polype,  offers  an  exam- 
ple, for  this  animal  seeks  the  sunny  side  of  the  vessel  in  which  it  is 
placed,  preferring  it  to  the  shade.  In  the  absence  of  every  vestige  of  a 
visual  organ,  there  can  not  be  a  doubt  that  its  'movements  depend  on  the 
perception  of  warmth,  just  as  when  a  man  who  is  totally  blind  passes 
from  the  sun  into  the  shade,  his  feelings  at  once  notify  him  of  the  change. 
In  a  physiological  sense,  it  is  of  no  interest  to  us  to  inquire  into  the  phys- 
ical nature  of  this  effect,  whether  light  is  identical  with  heat,  or  whether, 
when  light  falls  upon  a  body,  it  turns  into  heat.  We  have  only  to  ac- 
cept it  as  a  fact  capable  of  abundant  experimental  proof,  that,  whenever 
rays  of  light  fall  on  a  surface,  that  surface  becomes  warm.  This,  as  we 
shall  now  find,  is  the  key  of  all  the  explanations  we  have  to  give. 

Dr.  Franklin  made  an  experiment  to  the  following  effect.  He  placed 
Dr.  Franklin's  on  the  snow,  on  a  sunshiny  winter  day,  pieces  of  cloth  of  dif- 
experiment.  ferent  colors — black,  yellow,  white,  etc.,  etc. — in  such  a  posi- 
tion that  the  sun's  rays  fell  equally  on  them.  After  a  certain  length  of 
time,  on  examining  them,  he  found  that  the  black  cloth  had  melted  its 
way  deeply  into  the  snow,  the  yellow  to  a  less  depth,  and  the  white 
scarcely  at  all.  He  therefore  drew  the  conclusion  that,  when  they  are 
receiving  light,  surfaces  become  warm  in  proportion  to  the  depth  of  their 
tint,  and  that,  of  all  surfaces,  one  having  a  velvety  blackness  is  most  sen- 
sitive, because  it  can  exert  the  most  powerful  absorbent  agency. 

On  this  principle  seem  to  be  constructed  the  ocelli  of  the  lower  tribes. 
Ocelli  of  lower  These  consist  of  a  collection  of  pigment  granules,  usually 
animals  con-  Of  a  re(j  biack  or  <jark  color,  seated  on  the  expansion  of  a 

structedon  .       n  . 

Franklin's  nervous  thread.  The  principle  which  is  clearly  contained  in 
principle.  ^s  mechanism  js  that  of  relieving  the  general  surface  from 


OPTICAL  PRINCIPLES   OF  THE   EYE.'  381 

the  impression  of  light,  or  rather  of  rendering  it  more  intense  by  central- 
izing it  upon  a  special  locality.  Such  a  construction  involves  at  once  a 
change  in  the  nervous  mechanism,  by  devoting  a  particular  system  of 
nerve  tubules  to  the  new  duty.  But,  notwithstanding  this  increasing 
complexity  of  structure,  the  physical  principle  is  still  as  simple  as  be- 
fore. It  is  indeed  almost  as  though  a  blind  man  should  paint  upon  his 
skin  a  black  space,  so  that,  as  in  Franklin's  experiment,  it  might  be 
more  sensitive  to  the  sun.  With  this  devotion  to  a  new  duty  the  nerv- 
ous tubules  doubtless  assume  an  isolated  function,  and  thus  there  arises 
a  nerve  of  special  sense.  The  ocelli  of  the  lower  animals  are  sometimes 
quite  numerous.  Fronl  this  a  new  power  is  at  once  derived,  the  power 
of  determining  the  position  of  the  source  of  light,  a  property  which  doubt- 
less becomes  more  perfectly  marked  in  proportion  to  the  number  and 
symmetry  of  arrangement  of  the  ocelli.  As  we  ascend  the  animal  series 
in  our  examination,  we  soon  find  that  complexity  is  being  introduced. 
A  membranous  hood,  arising  from  a  little  fold  of  the  external  tegument, 
shadows  forth  the  rudiment  of  an  eyelid,  and  seems  to  indicate  to  us  that, 
even  in  these  low  grades,  the  condition  which  we  shall  eventually  find 
so  strikingly  marked  in  the  high  ones  already  exists,  that  functional  ac- 
tivity involves  destruction,  and  that  the  sensory  mechanism  must  have 
its  period  of  repose. 

Approaching  the  more  highly-developed  conditions  of  the  organ  of 
vision,  we  may  next  consider  the  cases  presented  by  the  introduction  of 
eyes  of  insects  and  the  eyes  of  higher  mammalia.     In  these  converging  me- 
a  new  physical  principle  has  been  introduced,  the  optical    ia' 
property  of  the  convex  lens,  a  transparent  solid,  having  one  or  both  of 
its  surfaces  curved,  and  obtaining  therefrom  the  power  of  forming  repre- 
sentations, or  images  of  objects  which  may  be  in  front  of  it,  at  a  certain 
focal  distance  behind.     Such  images  are  seen  when  we  take  a  magnify- 
ing glass  or  a  convex  lens,  and,  holding  a  piece  of  paper  be-  The  focus  and 
hind  it  at  a  particular  point,  there  will  be  depicted  upon  the  its  variations 
paper  the  inverted  forms  of  whatever  objects  may  be  in  front.  ° 
That  distance  is  the  focal  length  of  the  lens.     But  we  may  farther  no- 
tice, and  to  this  observation  our  attention  will  be  required  hereafter,  that 
the  focal  length  is  variable.     If  the  object  be  near,  the  focal  length  is 
greater ;  if  distant,  it  is  less. 

The  instrument  known  as  the  camera  obscura  represents  the  optical 
construction  of  the  eye.  Upon  a  receiving  surface  or  screen,  The  camera 
placed  at  the  focal  distance  behind  its  lens,  images  are  depicted  obscura. 
of  whatever  objects  may  chance  to  be  in  front ;  but — and  this  is  a  remark 
of  interest  to  us  now — the  visual  range,  or  field  of  view,  is  quite  limited. 
In  animals,  the  perfection  of  whose  vision  requires  that,  instead  of  being 
restricted,  in  their  view  to  a  narrow  space,  they  should  be  able,  as  it 


382  STRUCTURE    OF   THE   EYE. 

were,  to  take  in  almost  a  hemisphere  at  a  glance,  this  extension  of  the 
visual  function  can  only  be  accomplished  in  one  of  two  different  ways. 
rent  con  ^°  use  ^e  illustration  we  have  been  employing,  it  may  be 
trivances  for  reached  by  having  innumerable  cameras  pointing  in  innumer- 
iSger  field  of  a^e  directions,  and  conveying  the  resulting  images  to  one 
view  by  the  common  surface,  or  by  having  one,  or  at  most  two,  camerse 
set  upon  a  movable  stand,  which  can  quickly  point  them  in 
any  direction,  and  so  enable  them  to  inspect  successive  fields  of  view 
with  almost  instantaneous  rapidity.  The  former  plan  is  resorted  to  in 
most  insects,  the  latter  in  man.  In  insects,  the  immobility  of  the  head 
upon  the  trunk  would  interfere  with  any  rapid  rotation  of  the  visual  or- 
gan ;  in  man,  the  facility  with  which  rotation  can  take  place  upon  the 
neck  as  on  an  axis,  and  the  movement  of  the  eye  in  its  orbit,  accom- 
plishes the  object  without  any  kind  of  difficulty. 

In  continuing  an  investigation  of  the  structure  of  the  eye,  it  is  con- 
venient to  consider  it  under  three  heads :  1st.  Its  optical  mechanism ; 
2d.  Its  nervous  mechanism ;  3d.  Its  accessory  apparatus. 

1st.  Of  the  Optical  Mechanism  of  the  Eye. 

The  human  eye  is  of  a  globular  form,  and  about  one  inch  in  diameter. 
The  human  I*  *s  no't  perfectly  spherical,  its  lateral  diameter  being  shorter 
e3Te-  than  its  antero-posterior  by  about  one  twentieth  part.  It  may 

be  described  as  consisting  of  three  coats,  which,  forming  a  shell,  contain 
transparent  media  and  the  optical  apparatus.  It  might  also  be  consid- 
ered as  arising  from  an  expansion  of  the  optic  nerve  into  an  almost 
spherical  cavity,  and  which,  being  fortified  by  certain  tissues  behind, 
has  a  dioptric  mechanism  in  front. 

The  coats  of  the  eye  are  three  in  number :  the  sclerotic,  the  choroid, 
and  the  retina.  The  sclerotic,  which  is  the  exterior,  is  a  white  fibrous 
membrane,  very  tough,  and  possessing  the  necessary  resistance  to  give 
mechanical  protection  to  the  parts  within.  Within  this  is  the  choroid,  a 
vascular  layer  or  tunic,  presenting  on  its  interior  the  black  pigment  which 
darkens  the  interior  of  the  eye.  The  innermost  coat  is  the  retina,  an  ex- 
pansion of  the  optic  nerve.  The  sclerotic  coat  is  perforated  in  front,  and 
into  the  circular  aperture  so  arising  the  transparent  cornea  is  let,  like  a 
watch-glass.  .  Many  anatomists,  however,  consider  that  the  cornea  is 
absolutely  continuous  with  the  sclerotic,  and  a  part  of  it ;  the  sclerotic 
and  the  choroid  are  united  round  the  edge  of  the  cornea  by  the  ciliary 
ligament.  The  iris  is  perforated  in  its  centre,  the  aperture  being  desig- 
nated as  the  pupil.  Posterior  to  the  iris  is  the  crystalline  lens,  the  space 
between  the  lens  and  the  cornea  being  filled  with  the  aqueous  humor,  in 
which  the  iris  floats,  dividing  it  into  two  regions,  called,  from  their  posi- 
tion, the  anterior  and  posterior  chambers.  All  the  rest  of  the  ,globe  be- 


STRUCTURE   OP  THE   EYE.  383 

tween  the  back  of  the  lens  and  the  retina  is  filled  with  a  substance  ex- 
tremely transparent,  and  known  as  the  vitreous  humor.  The  aqueous 
humor,  the  crystalline  lens,  and  the  vitreous  humor,  by  reason  of  their 
transparency,  offer,  therefore,  no  obstacle  to  the  passage  of  light. 

ILLUSTRATIONS   OF   THE   EYE. 

Fig.  196 :  #,  a,  sclerotic,  turned  over ;  &,  choroid ;  c,  <?,  ciliary  nerves 
traversing  sclerotic,  and  going  between  it  and  choroid ;  d,  retina ;  0,  vit- 
reous body ;  f,  crystalline  ;  g,  middle  section  of  iris  ;  A,  middle  section 
of  cornea ;  it  anterior  chamber ;  j9  posterior  chamber ;  &,  canal  of  Fonta- 
196.  na,  between  the  ciliary  circle  and  iris 

on  one  side,  and  sclerotic  and  cornea  on 
the  other. 

Fig.  197. 


Profile  view  of  the  eye.  Front  view  of  the  eye. 

Fig.  197  :  <z,  transparent  cornea ;  £,  &,  sclerotic  ;  £,  iris  ;  d,  pupil ;  6, 
ciliary  circle ;  /*,  choroid,  on  which  is  seen  the  dichotomous  termination 
of  the  ciliary  nerves  ;  <?,  ciliary  processes ;  A,  crystalline. 

SECTION   OF   THE   EYE. 

fig.  198 :  a,  upper  eyelid ;  &,  lower  eyelid,  showing  the  different  lay- 

ers  composing  them  ;  c,  c,  conjunc- 
tiva, reflected  from  posterior  face  of 
eyelid  upon  the  anterior  face  of  the 
globe  of  the  eye ;  d,  d,  orbito-oc- 
ular  aponeurosis,  prolonged  upon, 
e,  the  sheath  of  the  optic  nerve,  and 
sending  sheaths  to  the  muscles  ;  f, 
the  superior  rectus  ;  </,  the  inferior 
rectus ;  A,  A,  sclerotic,  re-enforced 
behind  by  sheath  of  optic  nerve, 

section  of  the  eye.  and  in  front  by  aponeurotic  expan- 

sion of  recti  muscles  ;  «',  transparent  cornea,  cut  to  show  its  lamellar  tex- 
ture ;  j,  j,  choroid  ;  &,  ciliary  circle ;  Z,  ciliary  body  and  processes  ;  m, 
iris  and  pupil ;  n,  n,  canal  of  Fontana ;  o,  o,  retina,  continuous  with  sub- 


384  STRUCTURE   OF   THE   EYE. 

stance  of  optic  nerve ;  j?,  ciliary  circle  of  Zinn ;  q,  g,  hyaloid  mem- 
brane ;  r,  capsular  artery,  lodged  in  hyaloid  canal ;  s,  s,  vitreous  humor 
and  its  cells  ;  t,  crystalline  and  its  capsule ;  u,  u,  canal  of  Petit ;  v,  an- 
terior chamber ;  #,  posterior  chamber. 

To  this  general  description  of  the  conformation  of  the  eye  may  be  add- 
ed a  few  remarks  on  each  of  its  constituent  parts. 

The  sclerotic  coat  consists  of  white  fibrous  tissue,  which,  in  addition 
The  sclerotic  to  the  use  before  mentioned,  affords  the  means  of  insertion  of 
coat.  the  muscular  mechanism  for  moving  the  ball.  It  is  thicker 

behind  than  in  front,  its  relative  thickness  differing  in  different  animals 
according  to  the  mechanical  circumstances  to  which  they  have  to  be  ex- 
posed. In  the  whale,  which  has  to  resist  the  pressure  of  a  deep  sea,  the 
sclerotic  is  an  inch  thick.  In  some  instances  cartilage  is  included  in  it, 
in  others  bone.  Besides  the  aperture  in  front,  into  which  the  cornea  is 
let,  there  is  another  behind  for  the  passage  of  the  optic  nerve.  This 
method  of  description,  though  very  convenient,  is,  however,  scarcely  cor- 
rect, if  we  consider  the  coats  of  the  eye  as  arising  from  expansions  of  the 
optic  nerve,  for  then  the  sclerotic  answers  to  the  exterior  investiture,  and 
the  tubules  of  the  nerve  gain  access  to  the  interior  of  the  eye  without 
passing  through  an  aperture,  properly  speaking.  The  place  at  which 
the  nerve  enters  is  not  in  the  optical  axis,  but  at  a  distance  of  about  its 
own  diameter  on  the  interior  side.  The  aperture  is  smaller  on  the  in- 
side of  the  sclerotic  than  on  the  outside;  thus  it  presents  a  conical  shape. 
It  is  not  a  single  hole,  but  rather  a  collection  of  sieve-like  openings, 
through  which  the  optic  tubules  pass. 

The  cornea,  which  is  let  into  the  sclerotic  in  front,  is  of  greater  curva- 
ture than  the  sclerotic.  Its  front  and  back  faces  are  parallel. 

The  cornea,    m.          ,     ..  ,  ,,      . -.  ,  .,  ,  .    J   . 

Though  it  seems  to  be  pellucid  as  glass,  it  has  a  very  intri- 
cate construction,  being  composed  of  at  least  five  separate  layers  ;  the 
innermost  one,  or  cornea  proper,  consisting,  it  is  said,  of  more  than  sixty 
lamellae. 

The  choroid  coat  is  arranged,  like  the  sclerotic,  for  the  passage  of  the 
Thechoroid:  optic  nerve.  The  iris  is  commonly  described  as  a  process 
its  arrange-  Of  ft.  The  choroid  is  a  sheet  of  blood  capillaries  arranged 

ment for intro-   .  ,  .   ,         ,  .•          , 

during  and  re-  m  two  layers,  an  arterial  and  a  venous,  in  such  a  way  as  to 
moving  blood.  gjve  ^6  utmost  freedom  of  access  for  the  arterial  blood  to 
the  retina  within.  The  veins  which  remove  this  blood  are  placed  in 
curved  forms,  and  are  designated  vasa  vorticosa ;  from  the  choroid  also 
the  dark  pigment  is  secreted.  Those  animals  in  which  it  is  absent  are 
called  albinos.  Near  to  the  iris  the  choroid  merges  in  the  ciliary  liga- 
ment, and  gives  forth  the  ciliary  processes,  being  covered  in  front  by  the 
ciliary  muscle. 

Fig.  199 :  a,  a,  section  of  sclerotic ;  £,  exterior  surface  of  the  choroid, 


THE   IRIS,  RETINA,  AND   HUMORS. 


385 


on  which  are  seen,  c,  c,  the  vasa  vorticosa ;  <#,  d,  ciliary  nerves ;  0,  ciliary 
ligaments ;  /*,  anterior  face  of  iris ;  <7,  pupil. 

Fig.  199.  Fig.  200. 


The  veins  of  the  choroid.  The  arteries  of  the  choroid. 

Fig.  200:  a,  a,  exterior  surface  of  the  choroid  and  the  iris,  showing  the 
arterial  network  of  these  two  membranes,  supplied  by  the  ciliary  arteries, 
which,  after  having  traversed  the  sclerotic,  divide  into,  5,  £,  posterior  cili- 
aries  for  the  choroid,  and  <?,  c,  anterior  ciliaries  for  the  iris. 

The  iris,  though  arising,  as  has  been  said,  from  the  choroid,  is  con- 
structed in  a  different  way,  its  tissue  mainly  consisting  of  un- 
striped  muscular  fibre,  except  in  the  case  of  birds,  which  present 
the  striped  variety.     It  is  extremely  vascular,  its  arteries  being  derived 
from  the  ciliary.     The  color  of  the  eye  depends  on  the  color  of  the  front 
of  the  iris ;  the  posterior  portion  is  covered  with  black  pigment. 

The  ciliary  muscle,  for  such  it  has  been  proved  to  be  by  Dr.  Wallace, 
of  New  York,  is  of  the  unstriped  kind ;  its  action  is  to  move  the  lens. 
In  birds  it  is  of  the  striped  variety. 

The  retina  intervenes  between  the  vitreous  humor  and  the  choroid 
coat ;  it  arises  from  the  tubules  of  the  optic  nerve,  which  have  _ 

„    -,     .  .  .  -,     .  ,  i     ,       The  retina. 

cast  off  their  covering  investitures  on  their  passage  through  the 
sclerotic.     It  extends  forward  to  the  ciliary  body ;  is  perfectly  trans- 
parent during  life,  though  it  soon  becomes  semi-transparent.     Its  struc- 
ture, a  knowledge  of  which  is  of  the  utmost  importance  in  the  theory  of 
vision,  will  be  presently  described. 

201.  In  the  optical  axis  of  the  eye  there  is  upon  the  ret- 

ina a  spot  of  about  the  twentieth  of  an  inch  in  diam- 
eter, called  the  yellow  spot  of  Soemmering.  Its  posi- 
tion is  shown  in  Fig.  201.  The  entrance  of  the  optic 
nerve  is  at  the  blind  spot  which  is  marked  at  some  dis- 
tance on  one  side.  The  vitreous  humor  is  contained  in 
spot  of  soem-  a  delicate  mesh  of  transparent  tissue,  which  The  vitreous 

causes  it,  when  removed,  to  present  the  aspect  humor- 
of  a  jelly.  •    In  front  it  receives  the  crystalline  lens,  which  is  contained 
in  a  closed  capsule.     Eound  the  lens  there  is  a  passage,  known  as  the 
canal  of  Petit,  which  enables  the  ciliary  muscle  to  move  the  lens.     The 

BB 


386  OPTICAL   ACTION   OF   THE   EYE. 

Analysis  of  the  vitreous  humor  shows  that  it  consists  of  water  contain- 
ing about  one  and  a  third  per  cent,  of  common  salt,  with  a  trace  of  al- 
bumen. 

The  crystalline  lens  is  a  double  convex  of  unequal  curvatures,  the  an- 
The  crystalline  terior  surface  being  the  flattest,  the  shape  changing  with  the 
lens.  period  of  life,  as  also  does  the  density  of  its  parts,  its  cen- 

tral portions  being  always  the  most  dense.  In  construction  it  is  ex- 
tremely complex,  being  made  up  of  fibres  ranged  side  by  side,  and  so 
forming  successive  lamina.  The  fibres  are  about  the  -^fa-^  part  of  an 
inch  thick.  The  refracting  power  of  the  lens  differs  at  the  centre  and 
circumference :  in  the  former  region  it  is  greater.  In  chemical  composi- 
tion, the  lens  consists  of  about  fifty-eight  per  cent,  of  water,  and  thirty- 
six  per  cent,  of  a  form  of  albumen  known  as  globulin. 

The  aqueous  humor  fills  up  the  space  between  the  lens  and  the  cornea : 
Aqueous  humor.  **  *s  c°mposed  of  water  containing  about  one  per  cent,  of 
common  salt. 

Of  the  Optical  Action  of  the  Eye. 

It  is  the  province  of  the  works  on  natural  philosophy  to  explain  how, 
Formation  of  wnen  ravs  °^  %nt  &H  upon  a  convex  lens,  or  upon  combi- 
images  by  nations  of  such  lenses,  an  image  of  the  object  will  form  at  the 
proper  focal  distance.  For  the  purposes  of  physiology,  it  is 
sufficient  to  receive  this  as  a  fact,  which  may  be  easily  illustrated  by  ob- 
serving the  images  of  external  objects  depicted  upon  a  sheet  of  white 
paper  when  a  convex  lens  or  magnifying-glass  is  held  at  a  particular 
distance  between  the  object  and  the  paper. 

In  making  such  an  experiment,  some  other  facts  which  concern  the 
Effect  of  dis-  physiologist  may  be  readily  demonstrated:  1st.  That  the 
tanceoftheob-  focal  distance,  that  is,  the  distance  between  the  lens  and  the 

ject  and  curv-  .  .,,..  />         -•  • 

ature  of  the  paper,  is  variable :  it  is  greater  for  objects  that  are  near,  less 
for  those  that  are  remote ;  2d.  That  lenses  of  different  curv- 
atures being  compared  together,  the  flatter  ones  have  the  longest  focus 
for  objects  at  the  same  distance ;  3d.  That  lenses  of  the  same  focus,  but 
of  different  diameters,  give  images  unequally  sharp,  an  indefiniteness  be- 
ing perceived  in  the  image  given  by  the  lens  of  large  diameter.  This  in- 
distinctness is  due  to  the  spherical  figure  of  the  lens,  and  would  not  have 
Spherical  and  occurred  had  the  surface  been  ground  to  another  conic  sec- 
chromatic  aber-  tion.  It  is  called  spherical  aberration  ;  4th.  Unless  the 
lens  be  of  very  long  focus,  or  its  aperture  or  diameter  be 
very  small,  the  edges  of  the  images  it  yields  will  be  fringed  with  rainbow 
colors,  and  thereby  a  second  cause  of  indistinctness  arises.  It  is  called 
chromatic  aberration.  This  aberration  may  be  destroyed  by  properly 
combining  together  lenses  made  of  different  refracting  media,  and  with 


THE   RECEIVING   SCREEN.  387 

surfaces  of  suitable  curvatures ;  a  combination  in  which  this  has  been  ef- 
fected is  termed  an  achromatic  lens ;  and  if,  at  the  same  time,  by  proper 
arrangements,  the  spherical  aberration  has  been  destroyed,  the  lens  is 
termed  aplanatic. 

Now  the  aqueous  humor,  as  bounded  by  the  cornea  in  front  and  the 
crystalline  lens  behind,  acts  as  a  convex,  and  therefore  con-  Conver  ent 
verging  lens,  and  to  this  effect  the  crystalline  itself  adds  pow-  media  of  the 
erfully,  the  two  conjointly  causing  the  images  of  external  ob-  eye' 
jects  to  form  upon  the  black  pigment.  These  images  are,  of  course,  in- 
verted. 

The  adjustment  of  the  eye  for  perfect  vision  of  objects  at  different  dis- 
tances is  accomplished  by  the  action  of  the  ciliary  muscle,  ^d'ustment  b 
the  requisite  movement  being  to  draw  the  lens  farther  from  the  ciliary  mus- 
the  black  pigment  when  the  object  is  near.     There  has  been  c 
much  controversy  as  to  the  manner  by  which  this  adjustment  for  dis- 
tance is  effected,  but  it  is  generally  now  agreed  that  it  is  done  in  the 
manner  just  mentioned.     There  has  also  been  a  difference  of  opinion  as 
respects  the  actual  screen  upon  which  the  images  form.     Some  of  the 
early  optical  writers  regarded  the  black  pigment  as  being  The  receiving 
that  receiving  surface,  an  opinion  which  has  been  universal-  screen  V3  the 
ly  abandoned,  the  function  having  been  of  late  attributed  to  aMnoUhe  ret- 
the  retina,  but,  as  it  appears  to  me,  on  totally  insufficient  ina- 
grounds.     The  arguments  against  the  retina,  both  optical  and  anatom- 
ical, are  perfectly  unanswerable.     During  life  it  is  a  transparent  medium, 
as  incapable  of  receiving  an  image  as  a  sheet  of  clear  glass,  or  the  at- 
mospheric air  itself;  and,  as  will  presently  be  found,  when  we  come  to 
describe  its  structure,  its  sensory  surface  is  its  exterior  one,  that  is,  the 
one  nearest  to  the  choroid  coat.     But  the  black  pigment,  from  its  perfect 
opacity,  not  only  completely  absorbs  the  rays  of  light,  turning  them,  if 
such  a  phrase  may  be  used,  into  heat,  no  matter  how  faint  they  may  be, 
but  also  discharges  the  well-known  duty  of  darkening  the  interior  of  the 
eye,  and  therefore  preventing  indistinctness  through  the  straying  of  the 
rays  of  light.     Perfection  of  vision  requires  that  the  images  should  form 
on  a  mathematical  superficies,  and  not  in  the  midst  of  a  transparent  me- 
dium.    The  black  pigment  satisfies  that  condition,  the  retina  does  not. 

Spherical  aberration  is  compensated  for  partly  by  the  increasing  dens- 
ity of  the  lens  toward  its  centre,  and  partly  by  the  action  Correction  for 
of  the  iris,  which  stops  such  rays  of  light  as  are  at  any  con-  spherical  aber- 
siderable  distance  from  the  axis  of  the  eye,  acting  in  the 
same  manner  as  a  perforated  plate  or  diaphragm  in  ordinary  optical  in- 
struments. 

It  does  not  appear  that  there  is  any  attempt  at  correcting  the  chromat- 
ic aberration  of  the  eye,  though  it  is  popularly  supposed  that  the  cornea, 


388  LONG  AND   SHOET   SIGHT. 

the  aqueous  humor,  the  lens,  and  the  vitreous  humor  act  to- 
Chromatic  ab-  ^  .  „  . 
erration  is  un-  gether  in  the  same  manner  as  the  different  pieces  of  glass  in 

corrected.  an  acnromatic  arrangement.  Optical  reasons,  however,  found- 
ed upon  the  constitution  and  refractive  powers  of  those  substances,  lead 
us  to  abandon  that  view,  and  in  a  theoretical  respect  to  regard  the  eye 
as  imperfect  in  this  particular. 

Adjustment  for  the  variable  intensity  of  light  is  effected  by  the  dilata- 
tions and  contractions  of  the  iris,  the  pupillary  opening;  of 

Adjustment  for  .  7       i       P          •      i     •       -,• 

the  intensity  which  varies  from  the  -?fc  to  the  -J  of  an  inch  in  diameter. 
We  are  thus  enabled  to  bring  to  the  same  degree  of  illumin- 
ating effect  upon  the  retina  lights  which  differ  in  brilliancy  in  the  pro- 
portion of  one  to  forty-five.  The  means  by  which  this  is  accomplished 
will  be  more  particularly  described  when  we  speak  of  the  nervous  mech- 
anism of  the  eye. 

It  has  been  already  observed  that  the  actual  field  of  view  at  a  given 
moment  is  quite  limited.  We  are  liable  to  deceive  ourselves  on  this 
point  from  the  rapidity  with  which  the  eyeball  can  be  directed  to  differ- 
ent parts  in  succession. 

In  what  has  been  said,  reference  is  made  to  a  perfect  eye ;  but  imper- 
Long  and  short  fections  are  very  common.  Two  may  be  more  particularly 
cSre^donb'y11  Pointed  out— long-sightedness  and  short-sightedness.  In 
spectacles.  the  former,  objects,  to  be  seen  distinctly,  must  be  placed 
farther  off  than  the  usual  distance ;  in  the  latter  they  must  be  brought 
nearer.  Long-sightedness  arises  from  the  flatness  of  the  lens  or  cornea, 
so  that  the  focal  images  given  do  not  fall  truly  on  the  black  pigment,  but 
would  be,  at  a  certain  distance,  exterior  to  it ;  hence  the  indistinctness 
that  results.  Short-sightedness  is  due  to  an  excess  of  curvature  in  the 
cornea  or  lens,  the  rays  forming  their  focal  images  before  the  black  pig- 
ment is  reached.  The  former  defect  may  be  removed  by  the  use  of  con- 
vex lenses  as  spectacles,  the  latter  by  concave.  It  is  often  said  that 
short-sightedness  is  a  defect  of  early  life,  long-sightedness  of  old  age. 
However  this  may  be  in  another  respect,  it  is  not  so  optically.  Indeed, 
cases  sometimes  occur  in  which  one  eye  is  affected  with  the  former  and 
the  other  with  the  latter  difficulty.  Very  frequently  the  two  eyes,  com- 
pared together,  will  be  found  differently  advanced  in  their  degree  of  im- 
perfection, and  hence  the  difficulty  of  obtaining  a  pair  of  spectacles, 
though  the  selection  is  attempted  to  be  made  out  of  a  large  assortment. 
In  such  cases,  each  eye  should  be  accommodated  with  a  lens  to  suit  it- 
self. 

Compared  with  the  organ  of  hearing,  the  eye  is  much  more  limited  in  its 
Limit  of  vision  action ;  for,  while  the  ear  can  distinguish  sounds  which  vary 
is  one  octave,  through  many  octaves,  the  eye  can  only  perceive  vibrations 
which,  to  use  the  language  of  acoustics,  differ  by  a  single  octave  only. 


EFFECTS   OF   HEAT.  389 

To  one  octave,  therefore,  its  range  is  limited.  The  extreme  red  ray,  which 
is  emitted  by  a  substance  just  becoming  red  hot  at  a  temperature  of 
1026°  Fahr.,  and  which  is  the  least  refrangible  that  can  affect  the  eye, 
is  caused  by  vibrations  that  are  exactly  half  as  frequent  as  the  extreme 
violet  ray  emitted  by  the  sun.  It  is  important,  in  the  explanations  we 
are  giving,  to  understand  that,  in  a  perfect  solar  spectrum,  the  distribution 
of  the  colored  spaces  is  totally  different  from  what  it  is  in  the  case  of  the 
prismatic.  In  such  a  spectrum,  as  produced  by  the  interference  of  rays 
passing  through  a  surface  of  glass  on  which  have  been  ruled  with  a  point 
of  a  diamond  parallel  lines  the  yfl-J-g-g-  °^  an  mcn  apart,  the  yellow  occu- 
pies the  middle  region,  and  from  this  the  light  grades  off,  terminating  at 
equal  distances  with  the  extreme  red  on  one  side  and  the  extreme  violet 
on  the  other.  The  circumstances  of  such  an  experiment  prove  that,  the 
wave  length  for  the  red  light  being  compared  with  that  for  the  yellow, 
and  also  for  that  of  the  violet,  they  bear  to  one  another  the  extraordinary 
and  simple  relation  of  1,  1J,  2,  establishing  the  assertion  just  made, 
that  the  extreme  limit  of  perception  of  the  eye  is  comprised  in  a  single 
octave. 

I  may  refer  to  the  experiments  published  by  myself  on  this  point,  and 
also  to  those  both  antecedently  and  subsequently  published 
by  M.  Melloni,  in  proof  of  the  unreliability  of  the  method  of  colored  rays  is 
examining  the  solar  spectrum  by  the  prism  in  the  manner  ™  j£e£°inu? 
introduced  by  Newton.     More  particularly  to  the  discussion  minating  pow- 
now  before  us  does  this  remark  apply ;   for  the  prism,  as  er* 
may  be  gathered  from  what  has  just  been  said,  spreads  out  the  colors  of 
light  unduly,  and  gives  false  indications  respecting  the  distribution  of 
heat.     There  can  now  remain  no  doubt,  although  the  prism  indicates  the 
contrary,  that  the  yellow,  or  brightest  ray  of  light,  is  the  hottest,  and 
that  the  warming  power  of  the  others,  orange,  green,  &c.,  follows  in  the 
order  of  their  luminous  <  intensity.     When  we  have  finished  a  descrip- 
tion of  the  nervous  mechanism  of  the  eye,  we  shall  find  that  the  expla- 
nation of  its  function  turns  on  the  admission  of  this  fact. 

The  eye  is  limited  in  another  respect ;  it  can  not  simultaneously  com- 
pare lights  which  differ  from  one  another  in  brilliancy  if  the  Limit  in  the 
one  should  be  upward  of  64  times  as  bright  as  the  other. 
The  more  luminous  overpowers  or  extinguishes  the  feebler,  of  lights. 
We  can  not  see  the  light  of  a  candle  if  we  hold  it  up  against  the  sun.  I 
may  again  refer  to  the  experiments  I  have  published,  establishing  that 
upon  this  fact  is  founded  the  most  exact  method  of  photometry  yet 
known. 

2d.   Of  the  Nervous  Mechanism  of  the  Eye. 
In  the  preceding  description  it  was  stated  that  the  retina,  commonly 


390  STEUCTUEE    OF   THE   EETINA. 

described  as  an  expansion  of  the  optic  nerve,  intervenes  between  the  vit- 
reous humor  and  the  choroid  coat. 

Regarding  it  as  composed  of  distinct  layers,  the  innermost  of  which, 
Construction  in  contact  with  the  hyaloid  membrane,  is  called  the  fibrous 
°fnd  Jacobs  Sra7  ^a7er'  ariges  fr°m  tne  tubules  of  the  optic  nerve,  which 
membrane,  have  cast  off  the  white  substance  of  Schwann ;  and  in  pass- 
ing, we  may  dwell  emphatically  upon  the  point  that  at  that  spot,  where 
it  exists  alone,  that  is  to  say,  where  the  optic  nerve  is  entering  the  eye, 
vision  can  not  be  performed.  Beneath,  or  outside  this  fibrous  layer, 
comes  the  gray  vesicular  layer:  it  is  analogous  to  the  vesicular  matter 
of  the  brain.  The  two  layers  thus  far  described  are  served  with  capillary 
blood-vessels  of  extreme  minuteness.  Outside  of  the  gray  vesicular  lay- 
er is  the  granular  layer,  which,  as  its  name  imports,  consists  of  a  conge- 
ries of  granules,  which  are  puobably  the  origin  of  the  vesicles,  new  ones 
arising  from  this  layer  continually.  Yet  again,  outside  of  the  granular 
layer,  comes  a  delicate  sheet,  known  as  the  membrane  of  Jacob,  but  which 
is  formed,  in  reality,  from  the  juxtaposition  of  a  set  of  rod-shaped  and 
conical  bodies,  the  thicker  ends  of  the  rods  being  outward,  the  thinner 
inward. 

ig.  202.  Fig.  202  shows  the  partial  detachment  of 

the  membrane  of  Jacob  from  the  exterior  of  the 
retina.  The  membrane  appears  as  delicate 
shreds,  and  may  be  advantageously  demon- 
strated after  the  removal  of  the  choroid,  the 
specimen  being  placed  under  water. 

In  the  preceding  description  I  have  followed 
the  course  usually  taken  by  former  anatomists, 
who  describe  the  retina  as  consisting  of  suc- 
cessive layers  or  strata,  but  much  more  philo- 
Membrane  of  Jacob.  sophical  views  are  obtained  by  considering  it  in 

Per  endicuiar  ^e  manner  introduced  by  H.  Miiller,  that  is  to  say,  in  its 
examination  radial  section.  From  this  it  appears  that  the  four  strata 
of  the  retina.  ^QyQ  ^^0,^^  y^  \t  Jacob's  layer  of  rods  and  cones  ;  2. 
The  granular  layer ;  3.  The  vesicular  layer ;  4.  The  fibres  of  the  optic 
nerve,  are,  in  reality,  all  connected  in  such  a  way  that,  passing  in  a  radial 
direction  as  respects  the  globe  of  the  eye,  all  these  different  elements  are 
successively  combined,  constituting  what  is  termed  the  radiated  fibre 
system.  Thus  from  each  of  the  proper  fibres  of  the  optic  nerve  a  thread- 
Eadial  fibre  like  body  passes  radially  through  the  thickness  of  the  retina, 
system.  including  in  its  outward  passage  a  vesicle,  and  again,  beyond 
that,  a  granule,  and,  still  farther,  a  cone,  and  terminating  in  a  rod ;  so 
that  from  the  extremity  of  the  rod  there  is  a  continuous  communication 
through  the  thickness  of  the  retina  to  the  fibres  of  the  optic  nerve ;  the 


THE   OPTIC  NERVES.  391 

rods  are  therefore  to  be  regarded  as  the  termination  of  the  optic  fibres. 
In  the  opinion  of  Miiller  and  Kolliker,  the  rods  and  cones  composing 
Jacob's  membrane  are  the  true  percipients  of  light,  communicating  their 
condition  to  the  fibres  of  the  optic  nerve  by  means  of  the  connection 
which  they  thus  maintain  with  it ;  or,  perhaps,  the  rods  and  cones  are 
conductors  of  the  luminous  impressions  to  the  nerve-cells  of  the  retina, 
which  constitute  a  ganglion  capable  of  perceiving  light,  and  the  fibres  of 
the  optic  nerve  merely  communicate  those  impressions  to  the  sensorium. 

Whichever  of  these  descriptions  we  may  follow,  the  physiological  fact 
which  I  desire  to  present  with  emphasis  still  remains  the  same.  It  is, 
that  the  sentient  or  receiving  part  of  the  retina  is  the  posterior,  that 
which  is  in  contact  with  the  black  pigment. 

The  second  pair  of  nerves,  from  which  the  retina  is  thus  derived,  are, 
from  their  function,  designated  the  optic  nerves.     They  do  The  optic 
not  enter  the  sclerotic  in  its  optical  axis,  but  at  a  little  dis-  nerves :  their 

*  .   .  .         chiasm  and 

tance  on  one  side,  and  obliquely — a  provision  doubtless  in-  passage  to  the 
tended,  in  a  measure,  to  avoid  the  occurrence  of  the  blind  bram< 
spot  on  the  centre  of  the  field  of  vision,  and  to  place  it  unsy  in  metrically 
in  the  two  eyes,  so  that  each  eye  shall  compensate  the  defect  of  the  oth- 
er. The  nerves  from  each  eye  converge  to  their  chiasm,  which  is  a  com- 
missure consisting  of  three  distinct  systems  of  tubules — an  anterior  set, 
which  are  commissures  between  the  two  retinas,  a  posterior  set,  commis- 
sures between  the  two  optic  thalami,  and  an  interior  set,  the  proper  tu- 
bules of  the  optic  nerve,  which  cross,  those  from  the  right  eye  going  to 
the  left  side  of  the  brain,  and  those  from  the  left  eye  going  to  the  right 
side  of  the  brain.  The  chiasm  is  therefore  to  be  regarded  as  a  complex 
structure,  its  posterior  region  being  independent  of  the  other  parts,  and 
existing  in  animals  in  which  the  optic  nerve  is  not  found,  as,  for  exam- 
ple, in  the  mole. 

Besides  the  optic  nerve,  which  is  exclusively  the  nerve  of  vision,  the 
collateral  parts  of  the  eye  are  supplied  from  various  sources.  „ 
The  third  pair,  or  motores-oculorum,  supply  the  superior,  in-  eye-ball  and 
ferior,  and  internal  recti  muscles,  the  inferior  oblique,  and  the  annexe  Parts- 
levator  palpebrae.  The  fourth  pair,  or  pathetici,  supply  the  superior  ob- 
lique or  trochlear  muscles.  Of  the  fifth  pair,  supplies  are  derived  from 
the  frontal  branch,  lachrymal,  the  ciliary,  and  the  infra-trochlear.  The 
sixth  pair,  or  abducent,  pass  to  the  external  recti :  supplies  are  also  de- 
rived from  the  sympathetic.  Of  these  nerves,  the  functions  are  very  va- 
rious ;  some  are  for  the  movement  of  the  ball,  or  for  general  sensibility 
of  the  surface,  or  for  the  movements  of  the  eyelids,  or  for  those  of  the  iris, 
and  some  for  the  lachrymal  apparatus. 


392  NERVOUS   ffliCHANISM   OF  THE   EYE. 


Of  the  Function  of  the  Nervous  Mechanism  of  the  Eye. 

The  reasons  have  already  been  given  for  considering  that  it  is  the 
The  black  pig-  black  pigment  which  acts  as  the  receiving  eft  optical  screen, 
ment,  and  not  and  not  the  retina.  If  no  other  argument  was  adduced  for 
the  receiving  departing  from  the  opinion  usually  expressed,  which  attrib- 
screen.  u^es  this  function  to  the  retina,  the  thickness  of  that  struc- 

ture would  be  sufficient ;  images  can  only  form  with  precision  or  sharp- 
ness upon  an  abrupt  surface.  And  since  it  is  now  indisputably  ascer- 
tained that  both  the  chemical  effect  and  the  heating  effect  of  the  rays  of 
light  depend  upon  their  absorption,  those  effects  being  in  direct  propor- 
tion to  the  completeness  with  which  absorption  is  taking  place,  we  are 
justified  in  inferring  that,  since  the  eye  is  sensible  to  rays  of  so  low  a 
degree  of  intensity,  and  to  each  of  the  colored  ones  equally,  its  screen  of 
reception  must  not  only  be  a  superficies,  but  likewise  a  black  one.  Such 
a  surface  the  black  pigment  is.  In  the  case  of  albinos,  and  animals  in 
which  the  black  pigment  is  imperfectly  developed,  the  receiving  surface 
or  screen  is  still  the  interior  of  the  choroid.  Under  such  circumstances, 
vision  must  be  indistinct. 

Recalling  what  has  been  said  respecting  the  diffuse  sensibility  of  the 
Heating  effect  lower  members  of  the  animal  series  to  light,  and  the  struc- 
on  the  pigment,  ture  of  ocelli,  it  accords  well  therewith  to  consider  that  the 
primary  effect  of  the  rays  of  light  upon  the  black  pigment  is  to  raise  its 
temperature,  and  this  to  a  degree  which  is  in  relation  to  their  intensity 
and  intrinsic  color ;  light  which  is  of  a  yellow  tint  exerting,  as  has 
been  said,  the  most  energetic  action,  and  rays  which  correspond  to  the 
extreme  red  and  the  extreme  violet  the  feeblest.  The  varied  images  of 
external  objects  which  are  thus  painted  upon  the  black  pigment  raise  its 
temperature  in  becoming  extinguished,  and  that  in  the  order  of  their  brill- 
iancy and  color ;  the  pigment  thus  discharging  a  double  duty,  as  a  sur- 
face of  extreme  sensibility  for  calorific  impressions,  and  also  as  darken- 
ing the  interior  of  the  globe. 

In  this  local  disturbance  of  temperature,  in  my  opinion,  the  act  of 
Manner  of  er-  v^011  commences,  this  doctrine  being  in  perfect  harmony 
ception  by  the  with  the  anatomical  structure  of  the  retina,  the  posterior 
surface  of  which  is  its  sensory  surface,  and  not  the  anterior, 
as  it  ought  to  be  if  the  explanation  usually  given  of  the  nature  of  vision 
is  correct ;  and  therefore,  as  when  we  pass  the  tip  of  the  finger  over 
the  surfaces  of  bodies,  and  recognize  warm  and  cold  spaces  thereupon, 
the  same  occurs  with  infinitely  more  delicacy  in  the  eye.  The  club- 
shaped  particles  of  Jacob's  membrane  are  truly  tactile  organs,  which 
communicate  to  the  sensory  surface  of  the  retina  the  condition  of  tern' 
peratura.  of  the  black  pigment. 


PHOTOGRAPHIC  RELATIONS  OF  THE  EYE.  393 

But  this  communication  of  a  variation  of  temperature  implies  a  varia- 
tion in  the  waste  and  repair  of  the  retina  itself,  for  there  can  be  no  doubt 
that  all  such  changes  are  accelerated  by  an  increase  of  heat,  and  dimin- 
ished by  its  decrease.  And  though  in  this  manner  the  origin  of  the  ac- 
tion which  has  been  set  up  is  calorific,  and  therefore  physical,  it  imme- 
diately becomes  converted  into  a  physiological  equivalent  in  the  meta- 
morphosis and  destruction  of  a  nervous  tissue. 

The  eye  can  not  perceive  rays  which  come  from  a  luminous  source 
the  temperature  of  which  is  lower  than  1000°  F.,  for  such  rays  can  not 
pass  through  a  stratum  of  water  or  through  the  humors  of  the  eye. 
Natural  philosophers,  in  making  a  distinction  between  light  and  heat, 
have  too  often  overlooked  the  fact  that,  though  thermometers  are  sensi- 
tive to  rays  of  every  sort,  the  eye  is  not.  Its  indications  are  complicated 
by  the  necessary  introduction  of  absorbent  media,  which  stop  all  rays 
the  refrangibility  of  which  is  low. 

Many  years  ago,  Count  Rumford,  from  a  limited  examination  of  cases, 
concluded  that  all  photographic  effects  are  the  effects  of  Photographic 
a  high  temperature.  From  an  examination,  continued  for  ff?tgts0f  "tfh 
many  years,  of  numerous  phenomena  of  the  same  class,  which  temperature. 
have  since  been  described,  I  have  come  to  the  same  conclusion.  The 
impinging  of  a  ray  of  light  on  a  point  raises  the  temperature  of  that 
point  to  the  same  degree  as  that  possessed  by  the  source  from  which  the 
ray  comes,  but  an  immediate  descent  takes  place  through  conduction  to 
the  neighboring  particles.  This  conducted  heat,  by  reason  of  its  indef- 
initely lower  intensity,  ceases  to  have  any  chemical  effect,  and  hence 
photographic  images  are  perfectly  sharp  on  their  edges.  It  may  be  dem- 
onstrated that  the  same  thing  takes  place  in  vision,  and  in  this  respect 
it  might  almost  be  said  that  vision  is  a  photographic  effect,  the  receiving 
surface  being  a  mathematical  superficies,  acting  under  the  preceding  con- 
dition. All  objects  will  therefore  be  definite,  and  sharply  defined  upon 
it,  nor  can  there  be  any  thing  like  a  lateral  spreading.  If  vision  took 
place  in  the  retina  as  a  receiving  medium,  all  objects  would  be  nebulous 
on  the  edges.  This  sharpness  and  grading  off  are  happily  illustrated  by 
the  metal  daguerreotype  and  paper  photograph  respectively. 

Perhaps  it  might  be  thought  that  the  sharpness  of  impressions  upon 
collodion  or  albumen  stands  in  opposition  to  what  is  here  Absorption  nee- 
said  respecting  the  inefficiency  of  translucent  media.  Those 
substances,  however,  would  be  totally  inert  unless  there  had  tion 
been  purposely  mingled  with  them  some  compound  of  easy  decomposi- 
bility,  capable  of  absorbing  the  "blue  rays,  which  are  in  these  cases  the 
effective  photographic  ones.  Such  a  compound  must  commonly  be  of  a 
yellow  color.  In  these  substances  the  absorption  takes  place  with  en- 
ergy the  moment  the  light  has  entered  their  surface.  In  the  Philosoph- 


394  FUNCTION   OF  THE   EETINA  AND   CHOROID. 

ical  Magazine,  September,  1840,  1  have  given  proofs  that  the  essential 
condition  of  the  chemical  activity  of  a  ray  of  light  is  its  being  thus  ab- 
sorbed. As  an  illustration  may  be  given  the  well-known  result,  that  if 
chlorine  and  hydrogen  be  exposed  to  the  sun,  they  unite  with  a  violent 
explosion,  but,  under  the  same  circumstances,  oxygen  and  hydrogen  will 
utterly  refuse  to  unite,  no  matter  how  long  the  period  of  exposure  may 
be,  nor  what  the  brilliancy  of  the  light  ;  and  the  difference  in  the  two 
cases  is  merely  this,  that  the  chlorine,  being  of  a  yellowish  color,  can  ab- 
sorb the  violet  light,  and  therefore  be  influenced  by  it  ;  but  the  oxygen, 
being  uncolored,  can  not.  For  photographic  effects,  as  well  as  calorific, 
the  essential  condition  is  absorption.  A  medium  like  the  retina,  which 
is  without  absorbing  action,  permits  rays  to  pass  through  it  without  any 
kind  of  effect,  but  a  surface  like  the  black  pigment,  which  receives  them 
all  equally,  whatever  their  color  may  be,  and  absorbs  them  all  equally, 
is  equally  affected  by  them  all. 

The  impression  arising  from  the  disturbed  condition  of  the  retinal 
Function  of  the  vesicles  is  carried  by  the  optic  tubules  to  the  chiasm  of  the 


two  chief  lay-    ^wo  nerves.      Apart  from  the  general  facts  elsewhere  pre- 

ers  of  the  reti-  -,.1  ,  .  />ITT 

naandthecho-  sented  by  physiology,  the  existence  of  a  bund  spot  at  the 
entrance  of  the  optic  nerve,  where  there  is  a  necessary  ab- 
sence of  vesicular  structure,  is  a  clear  proof  of  the  insensibility  of  the 
tubular  structure  to  the  influence  of  light.  Considering,  therefore,  the 
retina  as  typically  composed  of  three  layers,  one  of  tubules,  one  of  vesi- 
cles, and  one  of  granules,  and  these  in  health  being  perfectly  transparent, 
the  luminous  beams  pass  through  them  just  as  they  do  through  the  at- 
mosphere, without  exerting  the  slightest  effect  ;  and  as,  when  those  rays 
strike  the  opaque  surface  of  the  earth,  or  are  absorbed  by  the  sea,  heat  is 
disengaged  and  effects  ensue,  so  likewise,  when  they  have  reached  the 
black  pigment,  the  changes  I  have  been  designating  arise.  The  vesicu- 
lar layer  undergoes  rapid  metamorphosis,  the  effect  of  that  change  is 
transmitted  by  the  tubular  layer,  and  in  the  granular  the  germs  are  con- 
stantly arising  from  which  the  waste  of  the  middle  layer  is  repaired.  So, 
therefore,  the  tubular  layer  is  for  conduction,  the  vesicular  layer  for  waste, 
the  granular  layer  for  repair  ;  and  now  appears  the  significance  of  the 
construction  and  proximity  of  the  choroid  coat,  for  the  waste  of  the  ve- 
sicular layer  can  not  occur  save  under  the  oxidizing  influence  of  the  ar- 
terial blood,  nor  can  the  nutrition  of  the  granular  layer  be  accomplished 
except  under  the  same  condition.  Moreover,  the  resulting  products  of 
waste  require  to  be  quickly  removed,  and  it  is  not  possible  to  conceive 
the  construction  of  an  arrangement  better  adapted  for  this  triple  object 
than  that  which  the  choroid  presents.  On  the  old  view  of  the  nature  of 
vision,  the  construction  of  the  choroid  seems  to  be  without  significance. 
The  analogy  between  the  mechanism  of  the  retina  and  that  of  the 


SINGLE  VISION.  395 

skin,  so  far  as  waste  and  restoration  are  concerned,  can  not  fail  to  be 
noticed. 

The  effect  which  has  thus  been  communicated  to  the  vesicular  layer 
of  the  retina,  through  the  intervention  of  Jacob's  rods  and  T 

.°  interconnection 

cones,  is  now  earned  along  the  nervous  tubules  out  of  the  of  the  right  and 
globe  of  the  eye.  The  nerves  from  each  eye,  converging,  e  fc  cye> 
encounter  one  another  at  the  chiasm,  the  triple  structure  of  which  has 
already  been  described.  Here  it  is,  however,  to  be  understood  that, 
while  the  proper  optic  tubules  of  the  right  eye  go  to  the  left  brain,  and 
of  the  left  eye  to  the  right  brain,  the  anterior  band  of  commissural  tu- 
bules brings  the  two  eyes  into  a  special  relation  with  one  another,  the 
right  side  of  one  eye  corresponding  with  the  rignt  of  the  other,  and  the 
left  with  the  left ;  or,  to  put  the  same  statement  under  a  more  simple  yet 
more  instructive  form,  the  outer  side  of  one  eye  corresponds  with  the  in- 
ner of  the  other,  and  in  this  manner  the  two  retinas  become  as  if  they 
were  virtually  incased  the  one  within  the  shell  of  the  other,  an  arrange- 
ment which  obviously,  as  has  been  already  remarked,  compensates  in  a 
degree  for  the  blind  spot  of  each  eye,  and,  indeed,  eliminates  the  effect  of 
all  accidental  irregularities,  for  numberless  such  irregularities  must  exist, 
there  being  a  necessity,  for  example,  that  blood-vessels  should  cross 
through  the  sensitive  to  the  conducting  structures,  and  such  blood-ves- 
sels give  rise  to  lines  of  inertness. 

From  this  commissural  arrangement  it  comes  to  pass  that  each  retina 
possesses  regions  of  symmetry  with  the  other,  and  on  this  single  and 
singleness  of  vision  depends ;  each  point  of  the  outer  portion  double  vision, 
of  the  retina  of  the  right  eye  has  its  point  of  symmetry  in  an  inner  portion 
of  the  left,  and  when  from  a  distant  object  rays  fall  on  these  symmetrical 
points,  that  object  will  be  seen  single ;  but  if,  by  the  pressure  of  the  fin- 
ger or  otherwise,  we  compel  the  image  to  fall  in  one  of  the  eyes  upon 
another,  and,  therefore,  non-symmetrical  point,  the  object  at  once  becomes 
double.  It  should  be  remarked  that  this  exchange  of  symmetry  concerns 
only  the  lateral  divisions,  for  the  upper  portion  of  one  eye  corresponds 
with  the  upper  portion  of  the  other,  and  the  lower  with  the  lower. 

If  the  view  which  I  have  presented  respecting  the  scal^e  of  the  laby- 
rinth of  the  ear  be  correct,  that  singular  structure  finds  its  Analo     be_ 
equivalent  in  the  black  pigment  of  the  eye ;  for  though  we  tween  the  scalse 
only  know  in  an  indistinct  manner  the  physical  condition  of  andP.1sment- 
black  opacity,  we  may  be  certain  that  it  arises  from  total  interference  of 
rays,  and  such,  it  is  presumed,  is  the  office  of  the  scalaa  of  the  ear. 

Impressions  made  upon  the  retina  do  not  disappear  instantly,  but  grad- 
ually fade  away,  and  in  so  doing  occupy  a  certain  period  of  Duration  of 
time,  which  varies  with  the  brightness  of  the  original  light,  the  impressions 
existing  condition  of  the  eye,  and  the  illumination  to  which  it 


396  ERECT   VISION. 

is  exposed.  This  duration  of  impressions  is  commonly  estimated  at 
about  one  third  of  a  second.  It  is  a  phenomenon  analogous  to  that  of  the 
continuance  of  sound  in  the  ear,  and  subserves  an  important  purpose  of 
keeping  vision  continuous  and  distinct  during  the  winking  of  the  eyelids. 
Commonly  it  is  illustrated  by  referring  to  the  familiar  experiment  of  a 
stick  lighted  at  one  end  and  twirled  rapidly  round,  which  gives  rise  to 
the  appearance  of  a  continuous  fiery  circle.  Many  ingenious  and  interest- 
ing toys,  such  as  the  thaumatrope  or  wonder-turner,  act  on  this  principle. 

When  the  eye,  particularly  after  a  period  of  repose,  as  when  we  first 
Ocular  spectra  wake  in  the  morning,  is  turned  to  the  window  or  some  bright 
%^t,  an(^  ^en  cl°sed>  a  spectral  impression  is  for  a  long 
time  presented  to  the  mind.  If,  instead  of  closing  the  eyes 
after  looking  at  a  bright  light,  they  are  directed  to  some  white  surface,  a 
dark  spectral  appearance  of  the  luminous  object  is  seen.  The  explana- 
tion of  this  is  evidently  that  those  parts  of  the  retina  which  have  just 
undergone  change  are  less  fit  to  be  acted  upon  by  the  more  moderate 
light  to  which  they  are  now  exposed  than  those  which  have  hitherto  been 
unaffected.  Under  similar  circumstances  arise  what  are  termed  comple- 
mentary colors.  Thus,  if  we  intently  regard  a  red  wafer  on  which  the 
sun-rays  are  brightly  shining,  and  then  turn  our  eyes  away  to  a  feebly 
illuminated  white  wall,  a  green  spectre  of  the  wafer  will  be  seen ;  and  so 
of  other  colors.  The  complementary  tint  is  that  color  which,  added  to 
the  original  one,  forms  white  light.  The  explanation  of  these  colored 
spectra  depends  upon  the  principle  just  mentioned. 

There  have  been  few  optical  problems  more  warmly  contested  than 
that  of  erect  vision.  The  image  at  the  bottom  of  the  eye  is 

Erect  vision.    .  11.  •   t  n  •, 

inverted,  but  we  see  the  object  upright.  Some  have  supposed 
that  we  really  see  things  upside  down,  but  have  learned  to  correct  the 
error  by  the  sense  of  touch.  Doubtless  the  true  explanation  is  to  be 
found  in  the  anatomical  construction  of  the  eye.  It  should  be  borne  in 
mind  that  there  is  a  very  wide  difference  between  the  image  formed  at 
the  bottom  of  an  eye  as  we  look  at  it,  and,  if  such  an  expression  may  be 
used,  as  the  eye  itself  looks  at  it.  We  see  it  from  behind,  the  retina 
sees  it  from  the  front.  Or,  to  put  the  statement  perhaps  more  clearly, 
it  is  one  thing  to  look  at  the  images  on  the  ground  glass  of  a  camera  ob- 
scura  from  behind  the  instrument,  and  another  to  see  them,  as  it  were, 
from  the  interior  of  the  box.  The  two  positions  are  upon  the  opposite 
sides  of  a  vertical  axis,  round  which  we  may  consider  that  we  have  turn- 
ed, and  hence  the  lateral  inversion  is  corrected.  That  portion  of  the  im- 
age which,  seen  from  behind,  was  on  the  right  of  the  spectator,  is  on  his 
left  if  seen  in  front.  A  similar  event  must  ensue  in  the  case  of  the  ret- 
ina. As  we  have  seen,  it  is  its  posterior  face,  looking  at  the  black  pig- 
ment, which  is  its  sensitive  surface.  It  sees,  as  it  were,  looking  back- 


IDEAS   OF  SOLIDITY.  397 

ward,  but  not  forward,  and  hence  there  arises  a  correction  for  Lateral  inver, 
the  lateral  inversion.  This,  of  course,  implies  the  existence  sion  corrected 
of  some  structural  arrangement  which  shall  either  correspond-  y 
ingly  correct  the  vertical  inversion,  or  bring  back  the  lateral  to  its  orig- 
inal erroneous  state,  and  thereby  establish  a  harmony  of  position  in  the 
two  directions ;  and  if,  in  the  retina  itself,  the  means  exist  for  the  cor- 
rection of  inversion,  vertical  as  well  as  lateral,  by  changing  the  direction 
of  the  conducting  tubules,  it  necessarily  must  be  that  that  place  of  cor- 
rection is  where  the  retina  is  intersected  by  the  optical  axis  of  the  eye. 
I  think  it  is  to  be  greatly  regretted  that  we  are  not  bet-  Suggestion  re- 
ter  acquainted  with  the  construction  of  the  yellow  spot  of  JSJjJj^Jfjl 
Soemmering,  which  occurs  at  this  very  point.  The  ridge-  Soemmering. 
like  form  it  presents,  the  thin,  uncolored  spot  in  its  centre,  its  more  def- 
inite occurrence  in  those  animals,  as  man,  the  quadrumana,  and  some 
saurians,  the  axes  of  whose  eyes  are  nearly  parallel  to  one  another,  seem 
to  indicate,  in  a  very  significant  manner,  that  at  this  place  the  correction 
in  question  is  made.  There  are  many  ways  in  which  we  may  conceive 
this  to  be  done  by  varying  the  direction  of  the  nervous  tubules.  As  an 
illustration,  it  may  be  remarked  that  if,  through  a  small  hole  made  in  a 
sheet  of  paper,  a  number  of  threads,  the  end  of  each  of  which  is  fasten- 
ed to  the  back  of  the  sheet,  be  caused  to  pass,  under  the  condition  that 
they  do  not  cross  one  another  in  the  hole,  but  leave  its  aperture  open, 
their  direction  in  space  as  they  retire  from  the  hole  will  be  inverted  as 
respects  the  direction  in  which  they  approached  to  it.  The  analogy  be- 
tween such  an  aperture  and  the  foramen  of  Soemmering  is  too  striking  to 
be  overlooked. 

The  stereoscope,  invented  by  Professor  Wheatstone,  shows  to  what  an 
extent  our  ideas  of  the  solidity  of  objects  depend  on  the  dif- 
ferences of  the  images  in  each  eye.  By  reason  of  their  dif- 
ference of  position,  each  of  the  two  eyes  will  have  a  different  picture  upon 
its  black  pigment  of  any  solid  object,  and  the  mind,  combining  these  dis- 
similar pictures  into  one,  gathers  therefrom  the  idea  of  solidity.  If  thus 
we  offer  to  the  eyes  two  pictures  of  a  given  object,  presenting  the  same 
form  as  that  object  would  have  done  when  seen  from  each  eye  respect- 
ively, the  mind  combines  these  flat  pictures  together,  and  can  not  divest 
itself  of  the  idea  of  a  solid  body.  This  is  the  principle  of  the  stereo- 
scope. It  is  shown  by  this  instrument  that,  when  two  such  pictures  of 
different  sizes  are  used,  the  mind  combines  them  into  one  of  intermediate 
magnitude.  Probably  this  effect  is  involved  in  the  circumstance  that, 
when  we  look  at  an  object  unequally  distant  from  the  two  eyes,  we  still 
see  it  single.  When  two  images  of  different  colors  are  employed,  the 
mind  can  not  combine  them,  but  sees  first  the  one  and  then  the  other, 
the  brightest  one  continuing  the  longest. 


398  SUBJECTIVE   IMAGES. 

The  eye  is  adjusted  to  the  varying  intensities  of  light  by  the  motions 
of  the  iris,  which  admits  more  or  fewer  rays  according  to  its 

Adjustment  to  .  .  •> 

variations  of  state  of  contraction,  an  action  which,  on  certain  occasions,  is 
brightness.  ai(je(j  by  the  orbicularis  palpebrarum,  which,  "by  bringing 
the  eyelids  together,  limits  the  number  of  rays  passing  to  the  pupil.  In 
man,  the  muscular  fibres  of  the  iris  are  of  the  unstriped  form ;  in  birds 
they  are  striped.  Our  perceptions  of  the  intensities  of  light,  as  gather- 
ed from  the  state  of  the  iris,  can  never  be  so  distinct  as  the  indications 
for  sound  yielded  by  the  tensor  tympani  and  stapedius  muscles.  In 
birds,  however,  it  is  probably  different.  We  gather,  to  a  great  extent, 
our  notion  of  the  brilliancy  of  light  from  the  rapidity  of  structural  change 
taking  place  in  the  retina  itself. 

Although  many  images  may  be  simultaneously  existing  upon  the  ret- 
Concentration  *na'  ^e  mm(^  possesses  the  power  of  singling  any  one  of  them 
of  attention  on  out  and  fastening  attention  upon  it,  just  as  among  a  number 
of  musical  instruments  simultaneously  played,  one,  and  that 
perhaps  the  feeblest,  may  be  selected,  and  its  notes  exclusively  followed. 
These  phenomena,  however,  are  not  dependent  upon  any  peculiarity  of 
construction  of  any  of  the  organs  of  sense ;  and  as  the  mind  can  perceive 
the  images  of  external  things,  so  can  it  give  rise  to  spectral  illusions 
which  may  simulate  perfectly  the  aspect  of  external  forms.  The  anec- 
dotes of  such  occurrences  which  are  to  be  found  among  all  people  are  not 
the  fabrications  commonly  supposed.  The  mind  can  be  readily  deceived, 
even  in  spite  of  itself,  as  the  phenomena  of  the  stereoscope  prove ;  and 
spectres,  having  their  origin  in  natural  or  diseased  conditions  of  the  brain, 
may  accurately  replace  images  that  have  been  painted  in  the  eye.  It  is 
Sub'ective  im  sa^'  however,  that  we  may  readily  distinguish,  by  means  of 
ages,  and  test  a  simple  optical  test,  a  true  external  apparition,  if  any  ex- 
ists, from  a  phantom  of  diseased  imagination ;  for  by  press- 
ing duly  with  the  finger  on  the  ball  of  one  of  the  eyes,  external  objects 
are  at  once  doubled,  but  it  is  not  so  with  a  mental  illusion ;  and  we  may 
therefore  suspect  that,  even  in  the  best  authenticated  cases  of  the  ap- 
pearances of  these  unnatural  forms,  had  this  test  been  applied,  their  true 
character  would  have  been  ascertained ;  and  that,  since  none  of  them 
would  have  undergone  duplication,  they  would  at  once  have  been  detect- 
ed as  mere  hallucinations  of  the  mind. 

The  explanation  of  the  function  of  vision  which  I  have  given  on  the 
preceding  pages  might  be  termed  the  calorific  hypothesis,  since  it  rests 
essentially  on  the  fact  that  the  temperature  of  the  receiving  screen  of  the 
eye  is  raised  by  the  impinging  of  light  upon  it.  The  result  thus  far  is  of 
a  purely  physical  nature,  but  it  becomes  physiological  when  we  farther 
admit  that  changes  of  constitution  ensue  in  the  vesicular  structure  of  the 
retina.  These  changes  are  rendered  more  rapid  as  the  temperature  is 


ACCESSORY  APPARATUS.  399 

higher.  It  remains  now  to  add  that  this  is  only  one  manner  of  looking 
at  the  thing.  According  as  our  hypothesis  of  the  nature  of  light,  of  its 
relations  to  heat,  and  of  its  manner  of  establishing  chemical  changes  may 
be,  the  special  explanations  we  give  of  the  functions  of  the  eye  will  differ ; 
yet  there  is  such  a  relationship  among  these  hypotheses  that  Translation  of 
we  can,  without  any  difficulty,  convert  an  explanation  derived  the  calorific 

n  .  i  •         i     *       i   /»  -i  T  hypothesis  to 

irom  one  into  an  explanation  derived  from  another.  It  re-  other  forms  of 
ally  comes  to  little  more  than  a  translation  of  phraseology.  exPression- 
I  have  found  the  calorific  hypothesis  convenient,  because  we  are  led  to  it 
by  the  comparative  anatomy  of  the  eye  in  starting  from  the  ocelli  of  the 
lower  forms  ;  yet,  with  almost  equal  convenience,  the  function  might  have 
been  treated  otherwise,  viewing  light  as  arising  from  ethereal  undulations, 
the  additional  advantage  then  being  obtained  of  establishing  a  parallel- 
ism between  the  action  of  the  organ  of  sight  and  that  of  hearing.  Or, 
in  like  manner,  the  case  might  have  been  viewed  in  its  purely  chemical 
aspect,  photographically,  as  it  might  be  said,  the  destruction  of  the  vesic- 
ular structure  of  the  retina  through  the  agency  of  arterial  oxygen  being 
taken  as  the  primary  physical  act.  But  this,  again,  amounts  only  to  a 
different  mode  of  stating  the  same  effect,  since,  as  I  have  shown  (London 
and  Edinburgh  Philosophical  Magazine,  May,  1851),  all  chemical  changes 
accomplished  in  material  substances  are  occasioned  by  the  establishment 
of  vibratory  motions  therein,  and  Ampere  has  already  demonstrated  that 
all  the  phenomena  of  heat  may  be  explained  upon  the  doctrine  of  the  vi- 
brations of  the  constituent  molecules  of  bodies. 

Divesting  ourselves,  therefore,  of  any  farther  concern  in  making  a  se- 
lection among  the  various  hypotheses,  we  have  adopted  the  view  that  the 
change  of  the  retina  originates  in  a  calorific  disturbance,  because  it  ap- 
pears to  be  somewhat  more  convenient  for  our  use. 

It  is  to  be  understood  that  the  sensation  of  light  is,  however,  purely 
mental,  and  whatever  can  disturb  the  nutrition  or  waste  of  The  sensation 
the  retina  will  give  rise  to  luminous  impressions.  The  press-  of  light  purely 
ure  of  the  finger  on  the  ball  of  the  eye,  a  blow,  the  passage  n 
of  an  electric  current,  and  divers  other  causes,  will  at  once  produce  the 
appearance  of  light,  and  even  of  colors.  Heat  is  only  one  out  of  a  mul- 
titude of  agents  that  can  disturb  the  retina. 

3d.   Of  the  Accessory  Apparatus  of  the  Eye. 

The  accessory  apparatus  of  the  eye  consists  chiefly  of  the  eyebrows, 
the  eyelids,  the  Meibomian  glands,  the  lachrymal  mechanism,  and  the 
muscles  for  the  movement  of  the  ball. 

The  eyebrows  are  two  arches  of  integument,  covered  with  hair,  on  the 
upper  edge  of  the  orbit.  They  are  usually  classed  with  the  The  eyebrows 
appendages  of  the  eye  upon  the  supposition  that  they  protect  and  eyelids. 


400  THE  LACHRYMAL  APPARATUS. 

that  organ  from  undue  intensity  of  light,  or  preserve  it  from  the  ingress 
of  drops  of  sweat.  They  aid  greatly  in  the  expression  of  mental  emo- 
tions, but  perhaps  should  rather  be  looked  upon  as  among  the  remaining 
vestiges  of  the  hairy  tegument  which  affords  a  protection  to  the  entire 
skin  of  other  mammals  below  man  in  the  animal  series.  The  eyelids 
may  be  described  as  a  pair  of  valves,  the  upper  one  having  a  much  great- 
er latitude  of  motion  than  the  lower.  Their  use  is  to  afford  protection 
to  the  eye  by  closing  entirely  over  it,  more  particularly  during  sleep ;  to 
keep  its  optical  surface  moist  and  free  from  dust  by  their  winking  mo- 
tion. They  are  brought  into  action  by  the  contact  of  air  or  of  irritating 
particles,  through  the  fibres  of  the  fifth  and  facial  nerves,  or  by  the  agency 
of  light  upon  the  retina.  The  edges  of  the  lids  are  furnished  with  rows 
of  curved  hairs,  the  eyelashes,  which  add  greatly  to  the  protection  of  the 
delicate  organ  beneath,  while  permitting  vision  to  take  place  to  a  certain 
extent.  Opening  upon  the  edges  of  the  eyelids  are  the  foramina  of  the 
Meibomian  glands,  in  the  upper  lid  there  being  about  thirty,  in  the  low- 
er somewhat  fewer.  The  glands  themselves  are  imbedded  on  the  in- 
ternal surface  of  the  cartilage  of  the  lids,  and  afford  an  oily  secretion, 
which  discharges  the  double  duty  of  preventing  adhesion  of  the  lids,  and, 
by  its  relation  of  capillary  attraction,  hindering  the  overflow  of  the  water 
which  moistens  the  eye  upon  the  cheek. 

Of  the  lachrymal  apparatus,  it  may  be  said  that  in  the  same  manner 
The  lachrymal  tna*  we  breathe  upon  a  spectacle  glass  and  wipe  it  that  its 
apparatus.  surface  may  be  perfectly  clean,  so  it  is  necessary  for  the  op- 
tical action  of  the  cornea  that  its  surface  should  be  constantly  washed, 
and  even  more  so,  for  its  lamellated-  structure  is  such  that,  if  it  be  not 
kept  constantly  damp,  it  loses  much  of  its  transparency.  This  therefore 
renders  it  necessary  that  there  should  be  a  mechanism  for  the  supply  of 
water,  another  for  spreading  that  water  uniformly  over  the  surface  of  the 
cornea,  and  a  waste-pipe  for  carrying  any  surplus  away.  The  lachrymal 
gland  discharges  the  first  of  these  duties.  It  is  situated  in  the  upper 
and  outer  angle  of  the  orbit ;  its  secretion,  which  is  a  bitter  and  some- 
what saline  water,  is  brought  to  the  surface  of  the  conjunctiva  by  eight  or 
ten  little  ducts  arranged  in  a  row  for  the  purpose  of  equalizing  their  dis- 
charge. The  spreading  of  this  fluid  over  the  eye,  and  the  simultaneous 
wiping  of  the  surface,  is  accomplished  by  the  eyelids.  Usually  the  wa- 
ter that  has  been  employed  is  dissipated  by  evaporation  into  the  air;  but 
if,  by  reason  of  meteorological  circumstances,  such  as  the  dampness  of 
the  atmosphere,  or  by  the  supply  being  too  abundant,  there  should  arise 
an  excess,  it  is  carried  off  through  two  minute  orifices  which  are  upon  the 
edge  of  the  eyelids,  the  puncta  lachrymalia.  These  draw  off  any  collection 
of  water  that  may  have  accumulated  in  the  lachrymal  lake,  and,  carrying 
it  into  the  lachrymal  sac,  discharge  it  through  the  nasal  duct  into  the 


CEREBRAL  SIGHT.  401 

cavity  of  the  nose.  From  this  it  is  removed  by  evaporation,  the  current 
of  air  alternately  introduced  and  expired  affording  the  means  of  accom- 
plishing that  object  in  a  remarkable  manner.  But  should  the  secretion 
of  water  from  the  lachrymal  gland  become  excessive,  as  in  weeping,  this 
draining  mechanism  is  insufficient,  and  the  water  is  discharged  as  tears 
down  the  cheek. 

Of  the  muscles  for  the  'movement  of  the  eye,  the  description  has,  in 
part,  been  given  under  that  of  the  nerves.  It  may,  how-  Motions  of  the 
ever,  be  here  remarked  that  the  eyeball  is  moved  by  six  eyeball, 
muscles,  the  four  straight  and  the  two  oblique.  The  straight  muscles 
arise  at  the  optic  foramen,  and  are  inserted  into  the  sclerotic  in  the  four 
quadrantal  positions  above,  below,  right,  and  left.  The  action  of  each 
of  these  muscles  is  to  turn  the  eyeball  toward  itself;  when  they  contract 
all  together,  they  fix  it.  The  superior  oblique  muscle  arises  from  the 
same  place,  passes  through  a  pulley  beneath  the  internal  angular  process 
of  the  frontal  bone,  its  tendon  being  inserted  into  the  sclerotic  near  to 
the  entrance  of  the  optic  nerve.  The  inferior  oblique  rises  from  the  in- 
ner margin  of  the  superior  maxillary  bone,  passes  beneath  the  inferior 
straight  muscle,  and  is  inserted  into  the  sclerotic  on  its  outer  and  pos- 
terior part,  near  the  entrance  of  the  optic  nerve.  The  superior  oblique 
rolls  the  globe  inward  and  forward,  the  inferior  rolls  it  outward  and  back- 
ward ;  acting  together,  they  draw  the  globe  forward  and  converge  the 
axes  of  the  eyes.  The  nervous  supply  for  these  various  muscles  has  al- 
ready been  specified  in  page  334. 


CHAPTEE  XXI. 

OF  CEREBRAL  SIGHT  OR  INVERSE  VISION. 

Difference,  between  ordinary  Vision  and  cerebral  Sight. — Inverse  Vision  depends  on  the  Vestiges 
of  Impressions  existing  in  the  Brain. 

Condition  of  our  perceiving  these  Impressions  is  that  they  must  be  equal  in  Intensity  to  present 
Sensations. — Two  Methods  of  accomplishing  this  Equalization:  1st,  by  re-enforcing  the  old  Im- 
pressions ;  2d,  by  diminishing  the  present  Sensations. 

Emergence  of  old  Impressions  in  Sleep,  Fever,  Death. — Artificial  Emergence  of  such  Vestiges  by 
Protoxide  of  Nitrogen,  Opium,  etc. 

Cerebral  Sight  used  tekologically  to  indicate  the  Immortality  of  the  Soul. 

THE  perception  of  external  objects  depends  on  the  rays  of  light  enter- 
ing the  eye,  and  converging  so  as  to  produce  images  which  make  an  im- 
pression on  the  retina,  and,  through  the  optic  nerve,  are  recognized  by 
the  brain.  The  direction  of  the  influences,  so  far  as  the  observer  is  con- 
cerned, is  from  without  to  within,  from  the  object  to  the  brain. 

Cc 


402  INVEESE   VISION. 

But  the  inverse  of  this  is  possible.  Impressions  already  existing  in 
the  brain  may  take,  as  it  were,  an  outward  direction,  and  be  projected 
or  localized  among  external  forms ;  or  if  the  eyes  be  closed,  or  the  ob- 
server is  in  darkness,  they  will  fill  up  the  empty  space  before  him  with 
scenery  of  their  own. 

Inverse  vision  depends  primarily  on  the  condition  that  former  impres- 
sions, which  are  inclosed  in  the  optic  thalami  or  registering  ganglia  at 
the  base  of  the  brain,  assume  such  a  degree  of  relative  intensity  that 
they  can  arrest  the  attention  of  the  mind.  The  moment  that  an  equal- 
ity is  established  between  the  intensity  of  these  vestiges  and  sensations 
contemporaneously  received  from  the  outer  world,  or  that  the  latter  are 
wholly  extinguished,  as  in  sleep,  inverse  vision  occurs,  presenting  itself, 
as  the  conditions  may  vary,  under  different  forms,  apparitions,  visions, 
dreams. 

From  the  moral  effect  to  which  these  give  rise,  we  are  very  liable  to 
regard  them  as  connected  with  the  supernatural.  In  truth,  however, 
they  are  the  natural  result  of  the  action  of  the  nervous  mechanism,  which 
of  necessity  produces  them  whenever  it  is  placed,  either  by  normal,  or 
morbid,  or  artificial  causes,  in  the  proper  condition.  It  can  act  either  di- 
rectly, as  in  ordinary  vision,  or  inversely,  as  in  cerebral  sight,  and  in  this 
respect  resembles  those  instruments  which  equally  yield  a  musical  note 
whether  the  air  is  blown  through  them  or  drawn  in. 

The  hours  of  sleep  constantly  present  us,  in  a  state  of  perfect  health, 
Difference  be-  illusions  which  appear  to  address  themselves  to  the  eye  rath- 
aii^wakin^^f  er  ^nan  ^°  an7  other  sense,  and  these  commonly  combine  into 
lusions.  moving  and  acting  sceneries,  a  dream  being  truly  a  drama 

of  the  night.  In  certain  states,  appearances  of  a  like  nature  intrude 
themselves  before  us  even  in  the  open  day,  but  these,  being  corrected  by 
the  realities  with  which  they  are  surrounded,  impress  us  very  differently 
to  the  phantoms  of  our  sleep.  The  want  of  unison  between  such  im- 
ages and  the  things  among  which  they  have  intruded  themselves,  the 
anachronism  of  their  advent,  or  other  obvious  incongruities,  restrain  the 
mind  from  delivering  itself  up  to  that  absolute  belief  in  their  reality 
which  so  completely  possesses  us  in  our  dreams.  Yet,  nevertheless, 
such  is  the  constitution  of  man,  the  bravest  and  the  wisest  encounter 
these  fictions  of  their  own  organization  with  awe. 

If  we  measure  the  importance  of  events  occurring  to  us  by  their  fre- 
Frequencyof  (luenc7»  the  depth  of  the  impression  they  make,  the  influ- 
mentaihaiiuci-  ence  they  exert  on  our  own  individual  career,  or  have  ex- 
erted on  the  progress  of  the  whole  human  race,  there  are 
very  few  more  deserving  the  discussions  of  physiology  than  visual  hal- 
lucinations. With  respect  to  frequency,  it  may  be  reasonably  said  that, 
if  images  arise  in  the  mind  by  night  as  numerously  as  sensible  forms 


EFFECT  OF  THESE   ILLUSIONS.  403 

present  themselves  by  day,  it  is  not  likely  that  they  should  be  better 
borne  in  memory ;  but  of  the  thousands  of  objects  we  encounter  every 
day  of  our  lives,  how  few  there  are  that  we  can  distinctly  recollect  at  its 
close.  We  think  we  explain  this  wonderful  forgetfulness  by  saying  we 
have  paid  no  attention  to  them ;  and,  in  like  manner,  the  dreams  we  re- 
member are  perhaps  only  a  very  insignificant  proportion  of  those  which 
have  been  presented  to  the  mind. 

It  has  been  said  that  a  belief  in  apparitions  is  natural  to  every  man. 
However  much  we  may  dissent  from  the  correctness  of  such  a  Their  moral 
general  assertion,  there  can  be  no  doubt  that  it  has  a  founda-  effecfc- 
tion  in  truth.  The  faith  of  a  child  in  this  particular  is  only  gradually 
sapped  as  he  grows  up  to  be  a  man.  Nay,  even  in  mature  life  there  may 
always  be  found  those  who  have  an  unwavering  confidence  in  the  reality 
of  these  illusions,  and  many  of  these  are  persons  characterized  by  their 
moral  courage  and  love  of  truth.  I  have  just  remarked  that  few  things 
have  exerted  a  greater  influence  on  the  career  of  the  human  race  than  a 
firm  belief  in  these  spiritual  visitations.  The  visions  of  the  Arabian 
prophet  have  ended  in  tincturing  the  daily  life  of  half  the  people  of  Asia 
and  Africa  for  a  thousand  years.  A  spectre  that  came  into  the  camp  at 
Sardis  unnerved  the  heart  of  Brutus,  and  thereby  put  an  end  to  the  po- 
litical system  that  had  made  the  great  republic  the  arbiter  of  the  world. 
Another,  that  appeared  to  Constantine,  strengthened  his  hand  to  the  ac- 
complishment of  that  most  difficult  of  all  the  tasks  of  a  statesman,  the 
destruction  of  an  ancient  faith. 

But  these  were  all  impostures,  it  may  be  said.  Not  so ;  they  were 
no  impostures  of  the  persons  to  whom  they  are  reported  to  have  occurred, 
and  who  assuredly  firmly  believed  in  the  real  existence  of  what  they 
thought  they  saw.  To  the  two  or  three  instances  mentioned  above, 
scores  of  a  like  kind  might  be  added,  which  have  issued  in  the  commit- 
ting of  men  to  the  most  earnest  kind  of  work.  So  often  do  historians 
notice  an  element  of  this  kind  mingling  in  the  career  of  those  who  have 
made  the  deepest  mark  on  our  race,  that  some  are  to  be  found  who  as- 
sert the  necessity  of  such  a  condition  to  any  widespread  and  permanent 
political  event.  Whatever  we  may  think  of  such  a  conclusion,  the  prem- 
ises on  which  it  is  founded  are  well  worthy  of  our  consideration.  The 
physiologist  is  not  at  liberty  to  deny  that  lunatic  and  delirious  men  have 
faith  in  what  they  see.  Their  senses  may  deceive  them,  but  they  are 
not  impostors.  It  is  for  him  to  consider  how  phantoms  may  arise  in 
conditions  of  apparent  health  as  well  as  in  states  of  disease ;  in  the  tran- 
quillity of  the  solitary  man  as  well  as  in  the  feverish  excitement  of  the 
enthusiast. 

Visual  hallucinations  are  of  two  kinds,  those  which  are  seen  when  the 
eyes  are  open,  and  those  perceived  when  they  are  closed.  To  the  for- 


404  RETINAL    DISTURBANCE. 

Apparitions  mer,  the  designation  of  apparitions  ;  to  the  latter,  that  of  vis- 
and  visions.  jons  may  be  given.  Dreams  therefore  come  under  the  latter 

class. 

The  simplest  form  of  apparition  is  that  known  among  physicians  as 
Muscse  voli-  muscse  volitantes.  These  are  dark  specks,  like  flies,  which 
tantes.  seem  to  be  floating  in  a  devious  course  in  the  air.  They  are 
owing  to  disturbances  or  changes  in  the  retina.  They  often  appear  to 
occupy  the  dying. 

Of  visions  the  most  common,  because  they  can  be  voluntarily  pro- 
Remains  of  op-  duced,  are  those  which  depend  on  the  remains  of  impressions 
tic  impressions.  j[n  the  retina  and  optic  centres.  If,  when  we  awake  in  the 
morning,  our  eyes  are  turned  for  a  moment  to  a  window  or  other  bright 
object,  and  then  closed,  there  still  appears  to  the  mind  a  spectral  repre- 
sentation of  the.  object,  which  gradually  fades  away.  These  illusions  can 
be  caused  to  have,  as  it  were,  a  movement  in  the  dark,  space  before  us, 
answering  to  the  voluntary  rotation  of  the  eyeball.  Sometimes,  when 
the  light  is  not  sufficiently  intense,  or  the  nervous  organs  not  sensitive 
enough,  the  vision  does  not  make  its  appearance  on  the  closing  of  the 
eyelids,  but,  after  fastening  the  attention  on  the  position  in  which  it  is  ex- 
geatofa  ari-  Pecte<^  to.come,  it  slowly  emerges  at  last.  That  it  consists 
tions  and  vis-  in  a  real  impression  which  has  been  made  on  those  organs, 
)ns'  and  is  not  a  mere  product  of  the  unaided  imagination,  is  very 

clear  from  the  fact  that  we  may  discern,  by  attentively  considering  it, 
many  little  peculiarities  which  we  have  not  had'  time  to  notice  in  the 
original  object ;  thus,  if  there  has  been  a  lace  curtain,  or  other  such  well- 
marked  body  before  us,  we  can  not  only  see  in  the  vision  the  places 
where  its  folds  intersect  the  windows,  but  likewise,  if  the  impression  be 
a  good  one,  all  the  peculiarities  of  its  figured  pattern ;  and  that  our 
conclusions  in  these  respects  are  correct  is  proved  as  soon  as  we  re-open 
our  eyes. 

Between  apparitions  and  visions  is  an  intermediate  class,  of  which  it 
is  not  my  object  now  to  say  much;  they  may,  however,  be 

Deceptions.  ..        J        .J  \  .   7      .    /     .     J 

styled  deceptions.  These  take  their  origin  in  some  outward 
existing  reality,  and  are  exaggerations  of  the  fancy.  They  are  commonly 
encountered  in  the  evening  twilight,  or  in  places  feebly  illuminated.  Sir 
W.  Scott  says  of  children  that  lying  is  natural  to  them,  and  that  to  tell 
the  truth  is  an  acquired  habit.  If  they  are  thus  by  nature  prone  to  de- 
ceive those  around  them,  they  are  none  the  less  prone  to  deceive  them- 
selves. To  them,  a  white  object,  faintly  descried  in  the  obscurity,  is 
easily  expanded  into  a  moving  and  supernatural  thing. 

In  a  physiological  sense  I  consider  that  simple  apparitions  arise  from 
disturbances  or  disease  of  the  retina ;  visions  from  the  traces  of  im- 
pressions inclosed  at  a  former  time  in  the  corpora  quadrigemina  and  op- 


RETINAL  DISTURBANCE.  405 

tic  thalami.  In  their  most  highly-marked  state  the  former  may  "be 
treated  of  as  results  of  insanity  of  the  retina,  the  latter  as  of  cerebral 
vision. 

Disturbance  of  the  retina,  brought  on  by  any  cause  whatever,  may  give 
rise  to  simple  spectral  apparitions,  which,  as  the  circumstances  A  aritions 
change,  will  have  an  indefinite  contour  or  a  definite  form ;  nor  from  retinal 
are  they  merely  shades  and  shadows :  they  may  be  presented  disturbance- 
in  colors,  which,  however,  are  usually  dim  or  subdued.  Thus,  if,  the  eye- 
lids being  closed,  we  press  gently  with  the  tip  of  the  finger  on  the  inner 
or  outer  angle  of  one  of  the  eyes,  a  gray  spot  surrounded  by  colors  makes 
its  appearance  on  the  opposite  side  of  the  same  eye,  and  dances  about  as 
the  pressure  of  the  finger  varies.  With  a  more  extensive  and  heavier 
pressure  clouds  of  various  rainbow  tints  fill  up  all  the  imaginary  space 
before  us.  In  like  manner,  the  passage  of  an  electric  current  from  a  vol- 
taic pair  induces  a  flash  of  light  of  considerable  brilliancy.  Internal 
pressures  and  spontaneous  variations  in  the  rate  of  metamorphosis  and 
nutrition  of  the  retina  act  in  a  manner  analogous  to  external  disturbances. 

From  the  muscge  volitantes,  which  may  be  regarded  as  the  first  rudi- 
ments of  apparitions,  it  is  but  a  step  to  the  intercalation  of  simple  or  even 
grotesque  images  among  the  real  objects  at  which  we  are  looking ;  and, 
indeed,  this  is  the  manner  in  which  they  always  offer  themselves,  as  rest- 
ing or  moving  among  the  actually  existing  things.  I  do  not  undertake 
to  say  how  far  we  are  liable  to  practice  deception  upon  ourselves,  after 
the  manner  we  have  spoken  of  in  children,  when  we  have  once  detected 
the  fact  that  we  are  liable  to  this  infirmity.  An  inanimate  object — for  in- 
stance, a  stick — is  seen  upon  the  floor;  we  go  to  take  it  up;  we  find  there 
is  nothing  there ;  we  return  to  our  first  position,  but  we  can  observe  no 
shadow  or  other  reality  that  can  be  offered  as  an  explanation  of  what  we 
have  seen.  An  event  of  this  kind  predisposes  us,  perhaps,  to  return  to 
that  disposition  of  exaggeration  so  natural  to  our  early  life,  and  the  next 
time  the  retina  deceives  us  we  involuntarily  give  to  the  hallucination  mo- 
tion and  a  more  definite  form. 

Insects  flying  in  the  air,  or,  rather,  floating  in  vacancy  before  us,  pre- 
sent the  incipient  form  of  retinal  malady.  It  may  be  provoked  by  un- 
due use  of  the  eyes,  as  reading  by  lamp-light.  I  remark  it  constantly, 
in  my  own  case,  after  prolonged  use  of  the  microscope.  In  a  more  ag- 
gravated form,  it  less  frequently  occurs  as  producing  stars  or  sparks  of 
light.  From  the  earliest  times,  physicians  have  observed  that  it  is  a 
"bad  sign"  when  the  patient  localizes  these  images.  "  If  the  sick  man 
says  there  be  little  holes  in  the  curtains,  or  black  spots  on  his  bed- 
clothes, then  is  it  plain  that  his  end  is  at  hand." 

Under  the  title  of  pseudoblepsis,  or  false  vision,  medical  authors  enu- 
merate several  varieties  of  the  foregoing  phenomena ;  but  when,  as  is 


406  HALLUCINATIONS   OCCASIONED   BY   DRUGS. 

Co-existence  most  commonly  the  case,  the  derangement  which  gives  origin 
of  retinal  in-  t  these  appearances  is  not  limited  to  the  retina,  but,  arising 

sanity  and  cer-   ,  . 

ebrai  sight.  in  some  constitutional  affection,  involves  more  or  less  com- 
pletely the  entire  nervous  apparatus  of  the  eye,  retinal  insanity  and  cerebral 
vision  occur  together.  In  those  cases  which  have  been  investigated  in 
a  philosophical  manner  by  the  patients  themselves,  this  complication  is 
often  distinctly  recognized.  Thus  Nicolai,  the  Prussian  bookseller,  who 
published  in  the  Memoirs  of  the  Royal  Academy  of  Berlin  an  interesting 
account  of  his  own  sufferings,  states  that,  of  the  apparitions  of  men  and 
women  with  which  he  was  troubled,  there  were  some  which  disappeared 
on  shutting  the  eyes,  but  some  did  not.  In  such  a  case  there  can  be  no 
doubt  that  the  disease  affected  the  corpora  quadrigemina  and  the  optic 
thalami  as  well  as  the  retina. 

This  condition,  in  which  the  receiving  centres  and  registering  ganglia 
at  the  base  of  the  brain  are  engaged,  is  the  one  which  yields  the  most 
striking  instances  of  hallucinations  in  which  apparitions  and  visions  co- 
Brought  on  ar-  exist.  It  can,  like  the  less  complicated  forms,  be  brought 
tificiaiiy  by  ai-  artificially,  as  in  the  delirium  tremens  which  follows  a 

conol,  opium,  •>  7 

&c.  cessation  from  the  customary  use  of  alcohol,  or  in  the  exalt- 

ation by  the  purposed  administration  of  opium  or  other  drugs.  In  this, 
as  in  those  forms,  it  is  the  localization  of  the  phantom  among  the  bodies 
and  things  around  us  that  begins  to  give  power  to  the  illusion.  The 
form  of  a  cloud  no  bigger  than  the  hand  is  perhaps  first  seen  floating 
over  the  carpet,  but  this,  as  the  eye  follows  it,  takes  on  a  sharp  contour 
and  definite  shape,  and  the  sufferer  sees  with  dismay  a  moping  raven  on 
some  of  the  more  distant  articles  of  furniture.  Or,  out  of  an  indistinct 
cloud,  faces,  sometimes  of  surprising  loveliness,  emerge,  one  face  succeed- 
ing as  another  dies  away.  The  mind,  ever  ready  to  practice  imposture 
upon  itself,  will  at  last  accompany  the  illusion  with  grotesque  or  even 
dreadful  inventions.  A  sarcophagus,  painted  after  the  manner  of  the 
Egyptians,  distresses  the  visionary  with  the  rolling  of  its  eyes.  Martin 
Luther  thus  more  than  once  saw  the  devil  under  the  well-known  form 
popularly  assigned  to  him  in  the  Middle  Ages. 

As  the  nervous  centres  have  been  more  profoundly  involved,  these 
Visions  of  false  visions  Become  more  impressive.  Instead  of  a  solitary 
or  exaggerated  phantom  intruding  itself  among  recognized  realities,  as  the 
shade  of  a  deceased  friend  qpens  the  door  and  noiselessly 
steps  in,  the  complicated  scenes  of  a  true  drama  are  displayed.  The 
brain  becomes,  as  it  were,  a  theatre.  According  as  the  travel  or  the 
reading  of  the  sick  man  may  have  been,  the  illusion  takes  a  style :  black 
vistas  of  Oriental  architecture,  that  stretch  away  into  infinite  night;  tem- 
ples, and  fanes,  and  the  battlemented  walls  of  cities  ;  colossal  Pharaohs, 
sitting  in  everlasting  silence,  with  their  hands  upon  their  knees.  "  ] 


FORMS  OF  SPECTKES.  407 

saw,"  says  De  Quincey,  in  his  Confessions  of  an  Opium-eater,  "  as  I  lay 
awake  in  bed,  vast  processions,  that  passed  along  in  mournful  pomp ; 
friezes  of  never-ending  stories,  that  to  my  feelings  were  as  sad  and  sol- 
emn as  if  they  were  stories  drawn  from  times  before  (Edipus  or  Priam, 
before  Tyre,  before  Memphis ;  and,  at  the  same  time,  a  corresponding 
change  took  place  in  my  dreams ;  a  theatre  seemed  suddenly  opened 
and  lighted  up  within  my  brain,  which  presented  nightly  spectacles  of 
more  than  earthly  splendor." 

Apparitions  are  the  result  of  a  false  interpretation  of  impressions  con- 
temporaneously made  on  the  retina ;  visions  are  a  presentment  of  the 
relics  of  old  ones  which  yet  remain  in  the  registering  ganglia  of  the 
brain.  We  convince  ourselves  of  the  truth  of  this  general  assertion  not 
so  well  from  an  examination  of  one  or  more  well-related  or  authenticated 
cases  as  from  what  may  be  termed  the  natural  history  of  ghosts..  The 
Greeks  and  Eomans  of  antiquity  were  just  as  much  liable  to  Secular  varia- 
disorders  of  the  nervous  system  as  we  are,  but  to  them  su-  ^ecT^nd^os^" 
pernatural  appearances  came  under  mythologic  forms,  Venus,  tume  of  spirits. 
and  Mars,  and  Minerva.  The  places  of  these  were  taken  in  the  dreams 
of  the  ascetics  of  the  Middle  Ages  by  phantoms  of  the  Virgin  and  of  the 
saints.  At  a  still  later  time,  in  Northern  Europe,  and  even  in  England, 
where  the  old  pagan  superstitions  are  scarcely  yet  rooted  out  of  the  vul- 
gar mind,  even  though  the  Reformation  has  broken  the  system  of  ecclesi- 
astical thought,  fairies,  and  brownies,  and  Robin  Goodfellow  survive. 
The  form  of  phantoms  has  changed  with  change  of  the  creeds  of  commu- 
nities, and  we  may  therefore,  with  good  Reginald  Scot,  inquire,  "  If  the 
apparitions  which  have  been  seen  by  true  men  and  brave  men  in  all  ages 
of  the  world  were  real  existences,  what  has  become  of  the  swarms  of 
them  in  these  latter  times  ?" 

One  class  of  apparitions — perhaps  it  was  the  first  to  exist,  as  it  is  the 
last  to  remain — has  survived  all  these  changes — survived  them  because 
it  is  connected  with  a  thing  that  never  varies — the  affection  of  the  hu- 
man heart.  To  the  people  of  every  age  the  images  of  their  dead  have 
appeared.  They  are  not  infrequent  even  in  our  own  times.  It  would 
be  an  ungracious  task  to  enter  on  an  examination  of  the  best  authenti- 
cated of  such  anecdotes.  Inquiries  of  this  kind  can  scarcely  be  freed 
from  the  liability  to  an  imputation  on  personal  veracity,  perceptive  pow- 
er, or  moral  courage ;  and,  after  all,  it  is  not  necessary  to  entangle  our- 
selves with  these  causes  of  offense.  It  is  enough  for  us  to  perceive  that 
even  here  incongruities  may  be  pointed  out.  The  Roman  saw  the  shade 
of  his  friend  clothed  in  the  well-known  toga ;  the  European  sees  his  in 
our  own  grotesque  garb.  The  spirit  of  Maupertuis,  which  stood  by  the 
bay  window  of  the  library  at  Berlin,  had  on  knee-breeches,  silk  stock- 
ings, and  shoes  with  large  silver  buckles.  To  the  philosopher  it  may 


408  SPECTRES   ORIGINATE   IN   PAST   EVENTS. 

perhaps  occur  that  it  is  very  doubtful  if,  among  the  awful  solemnities  of 
the  other  world,  the  fashions  ever  vary.  Let  us  pause  before  we  carry 
the  vanities  of  life  beyond  the  grave. 

From  such  reflections  as  the  preceding,  I  think  it  may  therefore  be 
concluded  that  there  are  two  sources  from  which  spectral  appearances  are 
derived :  1st.  Disturbance  of  the  retina,  which  presents  masses  of  light 
and  shade  or  colors  to  the  mind,  and  these  are  worked  by  the  fancy  into 
definite  forms  on  the  same  principle  that  we  figure  to  ourselves  pictures 
of  faces  among  glowing  embers.  This  constitutes  retinal  insanity.  2d. 
Gradual  emergence  from  the  registering  ganglia  of  the  brain  of  old  im- 
pressions, which  are  rendered  as  intense  and  distinct  as  contemporaneous 
sensations.  The  two  forms  may,  however,  coexist.  Of  the  latter,  I  may 
observe  that  the  views  of  Dr.  Hibbert,  in  his  work  on  Apparitions,  appear 
to  me  to  approach  nearer  to  the  truth  than  those  of  any  other  author.  It 
will  be  perceived,  however,  after  perusing  his  interesting  book,  that  I.  have 
not  laid  the  stress  he  has  done  on  the  mechanical  influence  of  the  circu- 
lation of  the  blood,  but  view  the  effect  as  of  a  more  purely  nervous  kind. 

As  the  emergence  of  old  images  which  have  been  registered  in  the  op- 
tic thalami  is  not  only  connected  with  the  physiological  explanations  we 
have  given  of  the  functions  of  the  brain,  but  also  occurs  under  circum- 
stances of  such  singularity  as  to  border  upon  the  supernatural,  we  may 
pursue  the  consideration  of  it  a  little  farther.  It  may,  I  think,  be  broad- 
Alls  ectrala  ^  asser^e(l  that  all  spectral  appearances  refer  to  things  that 
pearances  refer  are  past,  persons  who  are  dead,  events  which  have  taken 
place,  scenes  that  we  have  visited ;  or,  if  we  have  not  seen 
the  actual  reality,  then  pictures,  statues,  or  other  such  representations 
thereof.  It  has  never  yet  occurred  that  any  one  has  seen  a  phantom  the 
indications  of  the  bodily  presence  or  representation  of  which,  until  that 
moment,  he  had  never  known.  Thus,  in  the  Middle  Ages,  the  spectres 
of  African  negroes  were  common  enough,  but  no  man  ever  witnessed  one 
of  an  American  Indian,  yet  these,  in  their  turn,  prevailed  after  the  voy- 
age of  Columbus.  They  were  no  strangers  to  the  early  colonial  settlers. 
The  same  may  be  said  of  all  kinds  of  inanimate  objects. 

As  illustrating  the  manner  in  which  impressions   of  the  past  may 
.          emerge  from  the  registering  ganglia,  I  shall  here  famish  an 
the  emergence   instance  which  borders  closely  upon  the  supernatural,  and 
lions  i™ a.™*'    ^a^7  represents  the  most  marvelous  of  these  psychological 
etition  of         phenomena.     It  occurred  to  a  physician,  who  related  it  in 
my  hearing  to  a  circle  whose  conversation  had  turned  on  the 
subject  of  personal  fear.     "  What  you  are  saying,"  he  remarked,  "  may 
be  very  true,  but  I  can  assure  you  that  the  sentiment  of  fear,  in  its  ut- 
most degree,  is  much  less  common  than  you  suppose ;  and,  though  you 
may  be  surprised  to  hear  me  say  it,  I  know  from  personal  experience  that 


EMERGENCE   OF  OLD  IMPEESSIONS.  409 

this  is  certainly  so.  When  I  was  five  or  six  years  old,  I  dreamed  that  I 
was  passing  by  a  large  pond  of  water  in  a  very  solitary  place.  On  the 
opposite  side  of  it  there  stood  a  great  tree,  that  looked  as  if  it  had  been 
struck  by  lightning ;  and  in  the  pond,  at  another  part,  an  old  fallen  trunk, 
on  one  of  the  prone  limbs  of  which  there  was  a  turtle  sunning  himself. 
On  a  sudden  a  wind  arose,  which  forced  me  into  the  pond,  and  in  my  dy- 
ing struggles  to  extricate  myself  from  its  green  and  slimy  waters,  I  awoke, 
trembling  with  terror. 

"About  eight  years  subsequently,  while  recovering  from  a  nearly  fatal 
attack  of  scarlet  fever,  this  dream  presented  itself  to  me,  identical  in  all 
respects,  again.  Even  up  to  this  time  I  do  not  think  I  had  ever  seen 
a  living  tortoise  or  turtle,  but  I  indistinctly  remembered  there  was  the 
picture  of  one  in  the  first  spelling-book  that  had  been  given  me.  Per- 
haps, on  account  of  my  critical  condition,  this  second  dream  impressed  me 
more  dreadfully  than  the  first. 

"  A  dozen  years  more  elapsed.  I  had  become  a  physician,  and  was 
now  actively  pursuing  my  professional  duties  in  one  of  the  Southern 
states.  It  so  fell  out  that  one  July  afternoon  I  had  to  take  a  long  and 
wearisome  ride  on  horseback.  It  was  Sunday,  and  extremely  hot ;  the 
path  was  solitary,  and  not  a  house  for  miles.  The  forest  had  that  in- 
tense silence  which  is  so  characteristic  of  this  part  of  the  day ;  all  the 
wild  animals  and  birds  seemed  to  have  gone  to  their  retreats,  to  be  rid  of 
the  heat  of  the  sun.  Suddenly,  at  one  point  of  the  road  I  came  upon  a 
great  stagnant  water-pool,  and,  casting  my  eyes  across  it,  there  stood  a 
pine-tree  blasted  by  lightning,  and  on  a  log  that  was  nearly  even  with 
the  surface,  a  turtle  was  basking  in  the  sun.  The  dream  of  my  infancy 
was  upon  me ;  the  bridle  fell  from  my  hands ;  an  unutterable  fear  over- 
shadowed me  as  I  slunk  away  from  the  accursed  place. 

"  Though  business  occasionally  afterward  would  have  drawn  me  that 
way,  I  could  not  summon  the  resolution  to  go,  and  actually  have  taken 
roundabout  paths.  It  seemed  to  me  profoundly  amazing  that  the  dream 
that  I  had  had  should,  after  twenty  years,  be  realized  without  respect  to 
difference  of  scenery,  or  climate,  or  age.  A  good  clergyman  of  my  ac- 
quaintance took  the  opportunity  of  improving  the  circumstance  to  my 
spiritual  advantage ;  and  in  his  kind  enthusiasm,  for  he  knew  that  I  had 
more  than  once  been  brought  to  the  point  of  death  by  such  fevers,  inter- 
preted my  dream  that  I  should  die  of  marsh  miasm. 

"  Most  persons  have  doubtless  observed  that  they  suddenly  encounter 
circumstances  or  events  of  a  trivial  nature  in  their  course  of  life  of  which 
they  have  an  indistinct  recollection  that  they  have  dreamed  before.  It 
seemed  for  a  long  time  to  me  that  this  was  a  case  of  that  kind,  and  that 
it  might  be  set  down  among  the  mysterious  and  unaccountable.  How 
wonderful  it  is  that  we  so  often  fail  to  see  the  simple  explanation  of 


410  IMPRESSIONS   AND   SENSATIONS  EQUALIZED. 

things,  when  that  explanation  is  actually  intruding  itself  before  us.  And 
so  in  this  case ;  it  was  long  "before  the  truth  gleamed  in  upon  me,  before 
my  reasoning  powers  shook  off  the  delusive  impressions"  of  my  senses. 
But  it  occurred  at  last ;  for  I  said  to  myself,  Is  it  more  probable  that 
such  a  mystery  is  true,  or  that  I  have  dreamed  for  the  third  time  that 
which  I  had  already  dreamed  of  twice  before  ?  Have  I  really  seen  the 
blasted  tree  and  the  sunning  turtle  ?  Are  a  weary  ride  of  fifty  miles, 
the  noontide  heat,  the  silence  that  could  almost  be  felt,  no  provocatives 
to  a  dream  ?  I  have  ridden  under  such  circumstances  many  a  mile,  fast 
asleep,  and  have  awoke  and  known  it;  and  so  I  resolved  that  if  ever 
circumstances  carried  me  to  those  parts  again,  I  would  satisfy  myself  as 
to  the  matter. 

"Accordingly,  when,  after  a  few  years,  an  incident  led  me  to  travel 
there,  I  revisited  the  well-remembered  scene.  There  still  was  the  stag- 
nant pool,  but  the  blasted  pine-tree  was  gone ;  and  after  I  had  pushed 
my  horse  through  the  marshy  thicket  as  far  as  I  could  force  him,  and 
then  dismounted,  and  pursued  a  close  investigation  on  foot  in  every  di- 
rection round  the  spot,  I  was  clearly  convinced  that  no  pine-tree  had  ever 
grown  there ;  not  a  stump,  nor  any  token  of  its  remains,  could  be  seen ; 
and  so  now  I  have  concluded  that,  at  the  glimpse  of  the  water,  with  the 
readiness  of  those  who  are  falling  asleep,  I  had  adopted  an  external  fact 
into  a  dream  ;  that  it  had  aroused  the  trains  of  thought  which,  in  former 
years,  had  occupied  me ;  and  that,  in  fine,  the  mystery  was  all  a  delusion, 
and  that  I  had  been  frightened  with  less  than  a  shadow. " 

The  instructive  story  of  this  physician  teaches  us  how  readily,  and  yet 
how  impressively,  the  remains  of  old  ideas  may  be  recalled ;  how  they 
may,  as  it  were,  be  projected  into  the  space  beyond  us,  and  take  a  posi- 
tion among  existing  realities.  That  such  images  arise  from  a  physical 
impression,  which  has  formerly  been  made  in  the  registering  ganglia,  it 
is  impossible  to  doubt,  and  that  for  their  emergence  from  their  dormant 
state  it  is  necessary  that  there  should  be  a  dulling  or  blunting  of  con- 
Equalization  of  temporaneous  sensations,  so  that  these  latent  relics  may 
old  impressions  present  themselves  with  a  relatively  equal  force.  This 

and  new  sensa-  ,.        .  „  .  -,  -,    • 

tions  necessary  equalization  of  the  intensity  of  an  old  impression  with  a 
for  visions.  present  sensation  may  be  brought  about  in  two  different 
ways  :  1st.  By  Diminishing  the  force  of  present  sensations,  as  when  we 
Modes  of  ac-  are  in  a  reverie,  or  have  fallen  asleep,  or  by  breathing  vapors 
that^quaii?  unsuited  for  the  support  of  respiration ;  2d.  By  increasing  the 
zation.  activity  of  those  parts  of  the  brain  in  which  the  old  impres- 
sions are  stored  up.  On  each  of  these  a  few  remarks  may  be  made. 

Cerebral  vision  depends  on  an  equalization  in  intensity  between  pres- 
ent sensations  and  old  impressions.  So  long  as  the  former  predominate 
in  power,  the  latter  excite  no  attention  or  are  wholly  overlooked.  This 


EMERGENCE   OF   OLD   IMPRESSIONS.  411 

condition  is  illustrated  by  such  facts  as  that  the  flame  of  Illustrations  of 
a  candle,  held  against  the  sun,  is  utterly  overpowered  and  ^e^o^erin^ 
imperceptible,  but  is  seen  of  its  proper  brightness  when  it  each  other, 
is  in  presence  only  of  another  flame  like  itself;  or  as  the  stars,  which 
are  concealed  by  day,  are  plain  enough  when  the  sun  sets.  Ancient  im- 
pressions, harbored  in  the  optic  thalami,  can  not  make  themselves  felt 
against  sensations  just  establishing  themselves ;  for  as,  when  we  have 
looked  at  a  bright  window  and  then  closed  our  eyes,  the  retinal  phantom 
we  see  becomes  paler  and  paler,  and  after  a  while  dies  out,  so  do  cerebral 
images  undergo  a  diminution  of  intensity  with  lapse  of  time,  though  it 
may  be  questioned  whether  they  ever  entirely  wear  out.  The  law 
which  obtains  in  our  economy  for  other  organs  of  sense  applies  in  these 
cases  too.  Even  in  contemporaneously-occurring  sensations,  unless  there 
is  something  like  an  equality  between  them,  the  weaker  makes  no  im- 
pression upon  us.  In  the  presence  of  a  bright  light,  a  less  brilliant  one 
can  not  be  seen  ;  a  feeble  sound  is  made  inaudible  by  an  intensely  loud 
one ;  minute  variations  of  temperature  become  imperceptible  when  we 
are  submitted  to  a  great  heat  or  cold.  Ideas  are  no  more  than  the  ves- 
tiges of  what  were  once  sensations,  and  are  subjected  to  the  same  phys- 
ical law.  For  them  to  become  embodied,  and  to  cheat  the  mind  into  a 
belief  of  their  re-existence,  equivalent  in  all  regards  to  outward  and  actu- 
ally-existing things,  the  impressions  of  these  latter  must  be  diminished 
in  their  power,  or  the  vigor  of  the  former  must  be  re-enforced. 

So,  when  we  are  passing  away  in  sleep,  the  organs  of  sense  no  longer 
convey  their  special  impressions  with  the  clearness  and  force  Emero.ence  of 
that  they  did  in  our  waking  hours,  and  this  gives  to  the  de-  old  impressions 
caying  traces  which  are  stored  in  the  registering  ganglia  the 
power  of  drawing  upon  themselves  the  attention  of  the  mind. 

So,  likewise,  in  the  delirium  of  fevers,  the  spectral  phantoms  which 
trouble  the  sick  are  first  seen  when  the  apartment  is  dark-  Emer  ence  of 
ened  and  kept  silent,  and  especially  when  the  patient  closes  old  impressions 
his  eyes.  Until  the  senses  are  more  completely  overwhelm-  offe^ers^nTin 
ed,  these  shadows  will  disappear  on  brightly  illuminating  the  article  of 
the  room  or  on  opening  the  eyes.  And  so,  too,  in  the  hour 
of  death,  when  outer  things  are  losing  their  force  upon  the  dim  eye,  and 
dull  ear,  and  worn-out  body,  images  that  have  reference  to  the  manner 
of  our  past  life  emerge ;  the  innocent  and  good  being  attended  in  their 
solemn  journey  by  visions  in  unison  with  their  prior  actions  and  thoughts, 
the  evil  with  scenes  of  terror  and  despair ;  and  it  is  right  that  it  should 
Be  so. 

The  enfeebling  of  sensations  which  we  are  in  the  act  of  receiving 
from  external  sources,  so  as  to  bring  them  on  an  equality  with  those 
which  have  been  long  ago  impressed,  not  only  occurs  in  the  condition 


412  ACTION   OF   PROTOXIDE   OF  NITEOGEN. 

Emergence  of  of  sleep,  and  in  the  article  of  death,  but  may,  in  a  temporary 
old  impressions  manner  fog  established  by  resorting  to  certain  physical 

by  artificial  <*  o        ^  r   J 

means.  agents  and  drugs.    Pressure  upon  the  brain,  either  accident- 

ally or  purposely  applied,  is  well  known  to  produce  such  a  result,  and, 
in  like  manner,  the  inhalation  of  various  agents,  such  as  pure  hydrogen 
gas,  the  vapor  of  ether  or  chloroform,  or  other  non-supporters  of  respira- 
tion. On  breathing  these  substances,  anaesthesia  is  soon  induced ;  the 
external  world  disappears  ;  and,  on  carrying  forward  the  operation  to  a 
due  extent,  the  mind  and  the  brain  are  literally  left  to  themselves.  Opium 
acts  in  like  manner,  more  particularly  in  the  case  of  those  who  have  ac- 
customed themselves  to  its  undue  use.  It,  however,  not  only  blunts 
the  force  of  new  impressions,  but  exerts  a  positive  agency  in  intensifying 
the  decaying,  remains  of  old  ones.  Under  its  full  influence,  the  true  re- 
lations of  space  and  of  time  disappear :  a  century  of  events  is  lived 
through  in  a  single  night ;  the  vision  can  comprehend  distances  ap- 
proaching to  the  infinite ;  and  yet,  under  these  circumstances,  the  mind 
does  not  perceive  a  riot  of  incongruous  combinations,  but  every  thing  is 
presented  in  a  methodical  and  orderly  way — pictures,  all  the  parts  of 
which  are  in  just  proportions  and  severe  keeping  to  each  other,  and  long 
sequences  of  events  which  maintain  a  mutual  harmony. 

But,  as  I  have  just  remarked,  the  equalization  of  new  sensations  with 
Artificially  in-  old  impressions,  which  is  necessary  for  phantom  appearances, 
creased  func-  an(j  faQ  incarnation  and  outward  localization  of  ideas — that 

tional  activity   .  ,,..  ,.,..,. 

of  the  brain  in-  is,  cerebral  vision — may  take  place  by  heightening  or  re-en- 
creases  them.  forcing  the  old  impressions,  as  well  as  by  diminishing  the 
intensity  of  the  new  sensations ;  and  as  in  the  former  case,  so  in  this,  the 
result  can  be  reached  in  many  different  ways.  Whatever  will  cause  in- 
creased functional  activity  of  the  cerebral  structure  may  recall  these  old 
images  in  force.  It  is  almost  unnecessary  to  allude  to  the  delirium 
which  attends  inflammatory  states  of  the  brain.  Artificial  experiments 
are  more  instructive. 

For  the  purpose  of  increasing  the  functional  activity  of  the  cerebral 
Case  of  protox-  structure,  protoxide  of  nitrogen,  by  reason  of  its  greater  solu- 
ide  of  nitrogen,  bility  in  the  blood,  exceeds  in  power  even  oxygen  gas  itself. 
This  substance,  when  respired,  at  once  awakens  long  trains  of  vivid  ideas, 
the  recollection  of  all  kinds  of  former  scenes.  Its  action  is  divisible  into 
two  periods,  the  first  corresponding  to  the  heightened  sensibility  arising 
from  the  increased  oxidation  it  is  establishing  in  the  economy,  the  sec- 
ond to  the  depression  which  soon  comes  on  through  the  consequent  ac- 
cumulation of  carbonic  acid,  and  which  the  lungs  and  skin  are  unable 
with  sufficient  quickness  to  remove.  Sir  H.  Davy,  who  first  recognized 
its  physiological  power,  has  given  us  a  graphic  description  of  these  ef- 
fects. He  says,  "A  thrilling,  extending  from  the  chest  to  the  extremir 


REGISTERED   IMPRESSIONS.  413 

ties,  was  almost  immediately  produced.  I  felt  a  sense  of  tangible  exten- 
sion, highly  pleasurable,  in  every  limb.  My  visible  impressions  were 
dazzling  and  apparently  magnified.  I  heard  distinctly  every  sound  in 
the  room,  and  was  perfectly  aware  of  my  situation.  By  degrees,  as 
the  pleasurable  sensation  increased,  I  lost  all  connection  with  external 
things  ;  trains  of  vivid  visible  images  rapidly  passed  through  my  mind, 
and  were  connected  with  words  in  such  a  manner  as  to  produce  sensa- 
tions perfectly  novel.  I  existed  in  a  world  of  newly-connected  and 
newly-modified  ideas.  When  I  was  awakened  from  this  semi-delirious 
trance  by  Dr.  Kinglake,  who  took  the  bag  from  my  mouth,  indignation 
and  pride  were  the  first  feelings  produced  by  the  sight  of  the  persons 
about  me.  My  emotions  were  enthusiastic  and  sublime,  and  for  a  mo- 
ment I  walked  round  the  room  perfectly  regardless  of  what  was  said  to 
me.  As  I  recovered  my  former  state  of  mind,  I  felt  an  inclination  to 
communicate  the  discoveries  I  had  made  during  the  experiment.  I  en- 
deavored to  recall  the  ideas ;  they  were  feeble  and  indistinct.  One  rec- 
ollection of  terms,  however,  presented  itself,  and  with  the  most  intense 
belief  and  prophetic  manner  I  exclaimed  to  Dr.  Kinglake,  '  Nothing  ex- 
ists but  thoughts  ;  the  universe  is  composed  of  impressions,  ideas,  pleas- 
ures, and  pains.'" 

In  like  manner,  the  intoxication  that  arises  from  alcohol  has  two  dis- 
tinct stages,  depending  on  entirely  different  phases  of  its  chemical  action. 
At  first  there  is  an  exaltation  of  effects,  because  of  the  increased  function- 
al activity  established  ;  but  this,  after  a  time,  is  succeeded  by  a  dullness, 
or  even  stupefaction,  attributable  to  the  impression  which  the  carbonic 
acid  arising  from  the  oxidation  of  the  alcohol  is  making  upon  the  nerv- 
ous centres. 

By  two  different  methods,  therefore,  ancient  impressions  TWO  methods  of 
may  be  equalized,  as  respects  intensity,  with  new  sensations,  equalization  of 

r™         -  /•  ,1       r  i  T          .ii         /*>    ,     •/•    old  impressions 

The  vigor  of  the  former  may  be  increased,  or  the  effect  of  and  existing 
the  latter  diminished.  sensations. 

Equalized  in  any  way  in  their  force,  the  mind  is  ready  to  confound  its 
own  ideas  and  external  forms  together.  A  cause  which,  perhaps,  might 
seem  to  be  trivial,  fastens  the  attention,  and  at  once  a  solitary  form,  or 
even  the  machinery  of  a  long  drama,  emerges.  It  is  no  more  possible  for 
us  to  say  why  the  thought  runs  in  one  course  rather  than  another,  and 
lays  hold  of  image  after  image  in  succession,  than  we  can  foretell  the 
way  of  a  spark  that  moves  darkling,  on  the  ashes  of  a  piece  of  burned  pa- 
per. Yet  it  too  runs  in  connected  lines. 

No  better  evidence  can  be  given  that  the  images  we  are  speaking  of 
are  impressions  of  past  events  registered  in  the  brain,  and  which  gain 
the  power  of  drawing  upon  themselves  the  attention  of  the  mind,  either 
by  their  assuming  an  unwonted  intensity,  or  by  the  diminution  of  the  in- 


414  KEGISTEKED   IMPEESSIONS. 

fluence  of  newly-arriving  sensations,  than  the  philosophical 

Proof  of  the  ex-  .          • J  -,  j     i  /.    ,  , 

istence  of  im-  observations  which  have  been  made  by  some  of  those  who 
pressions  in  the  jiaye  ^een  ji^le  |o  these  infirmities  on  their  own  cases. 

registering  gan- 
glia and  their  Thus,  in  such  a  case  recorded  in  Nicholson's  Philosophical 
emergence.  Journai?  and  auuded  to  by  Dr.  Hibbert :  "I  had  a  visit," 
said  the  patient,  "from  Dr.  C ,  to  whom,  among  other  remarks,  I  ob- 
served that  I  then  enjoyed  the  satisfaction  of  having  cultivated  my  mor- 
al habits,  and  particularly  in  having  always  endeavored  to  avoid  being 
the  slave  of  fear.  '  I  think,'  said  I,  'that  this  is  the  breaking  up  of  the 
system,  and  that  it  is  now  in  progress  to  speedy  destruction.  In  this 
state,  when  the  senses  have  become  confused,  and  no  longer  tell  me  the 
truth,  they  still  present  me  with  pleasing  fictions,  and  my  sufferings  are 
mitigated  by  that  calmness  which  allows  me  to  find  amusement  in  what 
are  probably  the  concluding  scenes  of  life.'  I  give  these  self-congratula- 
tions without  scruple,  more  particularly  because  they  led  to  an  observa- 
tion of  fact  which  deserves  notice.  When  the  doctor  left  me,  my  relax- 
ed attention  turned  to  the  phantasms,  and  some  time  afterward,  instead 
of  a  pleasing  face,  a  visage  of  extreme  rage  appeared,  which  presented  a 
gun  at  me,  and  made  me  start ;  but  it  remained  the  usual  time,  and  then 
gradually  faded  away.  This  immediately  showed  me  the  probability  of 
some  connection  between  my  thoughts  and  these  images,  for  I  ascribed 
the  angry  phantasm  to  the  general  reflection  I  had  formed  in  conversa- 
tion with  Dr.  C .  I  recollected  some  disquisitions  of  Locke,  in  his 

treatise  on  the  Conduct  of  the  Mind,  where  he  endeavors  to  account  for 
the  appearance  of  faces  to  persons  of  nervous  habits.  It  seemed  to  me 
as  if  faces  in  all  their  modifications,  being  so  associated  with  our  recol- 
lections of  the  affections  of  passions,  would  be  most  likely  to  offer  them- 
selves in  delirium;  but  I  now  thought  it  probable  that  other  objects 
could  be  seen,  if  previously  meditated  upon.  With  this  motive  it  was 
that  I  reflected  upon  landscapes  and  scenes  of  architectural  grandeur 
while  the  faces  were  flashing  before  me,  and  after  a  considerable  interval 
of  time,  of  which  I  can  form  no  precise  judgment,  a  rural  scene  of  hills, 
valleys,  and  fields  appeared  before  me,  which  was  succeeded  by  another 
and  another  in  ceaseless  succession,  the  manner  and  times  of  their  respect- 
ive appearance,  duration,  and  vanishing  being  not  sensibly  different  from 
that  of  the  faces.  All  the  scenes  were  calm  and  still,  without  any  strong 
light  or  glare,  and  delightfully  calculated  to  inspire  notions  of  retirement, 
of  tranquillity,  and  happy  meditation."  The  same  writer  adds  in  anoth- 
er place,  "  The  figures  returned,  but  now  they  consisted  either  of  books, 
or  parchments,  or  papers  containing  printed  matter.  I  do  not  know 
whether  I  read  any  of  them,  but  am  at  present  inclined  to  think  that  they 
were  not  either  distinctly  legible,  or  did  not  remain  a  sufficient  time  be- 
fore they  vanished.  I  was  now  so  well  aware  of  the  connection  of  thought 


USE   OF  INVERSE   VISION.  415 

with  their  appearances,  that,  by  fixing  my  mind  on  the  consideration  of 
manuscript  instead  of  printed  type,  the  paper  appeared,  after  a  time,  only 
with  manuscript  writing ;  and  afterward,  by  the  same  process,  instead  of 
being  erect,  they  were  all  inverted,  or  appeared  upside  down." 

We  can  not  fail  to  remark  the  close  resemblance  between  these  illu- 
sions, arising  from  a  fixed  meditation  on  recollected  scenery,  E  .  ,  j  j 
and  the  phantoms  which  are  witnessed  after  our  gaze  has  izatkmofphan- 
been  steadily  directed  to  some  brightly-illuminated  object,  asms> 
as  a  window,  when  we  first  awake.  In  both  there  is  the  same  subdued 
and  uncertain  brilliancy  of  effect ;  in  both  the  same  gradual  fading  away ; 
in  both  the  mind  does  not  refer  the  image  it  contemplates  to  an  inward 
point  or  place,  but  sets  it  forth  outwardly,  projecting  it  into  the  empty 
or  occupied  region  beyond.  In  inverse  as  in  ordinary  vision,  the  law  of 
the  line  of  visible  direction  is  enforced,  and  this  reference  of  cerebral  im- 
ages to  a  definite  point  in  outer  space  is  a  phenomenon  of  the  same  kind 
as  the  appearance  of  the  invisible  coin  on  pouring  water  into  a  basin,  the 
lifting  of  ships  into  the  air  by  atmospheric  refraction,  the  appearance  of 
the  sun  and  moon  every  day  above  the  horizon  before  they  have  actu- 
ally risen  and  after  they  have  set,  and  many  other  optical  illusions  that 
might  be  mentioned. 

Physiology,  though  full  of  teleological  illustrations — that  is,  examples 
of  the  use  of  means  for  the  accomplishment  of  an  end — has  „,, 

^  Ine  nervous 

none  more  worthy  of  our  consideration  than  this  of  inverse  mechanism  con- 
vision.  Men  in  every  part  of  the  world,  even  among  na-  dkateefhe°im" 
tions  the  most  abject  and  barbarous,  have  an  abiding  faith  mortality  of  the 
not  only  in  the  existence  of  a  spirit  that  animates  us,  but 
also  in  its  immortality.  Of  these  there  are  multitudes  who  have  been 
shut  out  from  all  communion  with  civilized  countries,  who  have  never 
been  enlightened  by  revelation,  and  who  are  mentally  incapable  of  rea- 
soning out  for  themselves  arguments  in  support  of  those  great  truths. 
Under  such  circumstances,  it  is  not  very  likely  that  the  uncertainties  of 
tradition  derived  from  remote  ages  could  be  any  guide  to  them,  for  tra- 
ditions soon  disappear  except  they  be  connected  with  the  wants  of  daily 
life.  Can  there  be,  in  a  philosophical  view,  any  thing  more  interesting 
than  the  manner  in  which  these  defects  have  been  provided  for,  by  im- 
planting in  the  very  organization  of  every  man  the  means  of  constantly 
admonishing  him  of  these  facts,  of  recalling  them  with  an  unexpected 
vividness  before  him,  even  after  they  have  become 'so  faint  as  almost  to 
die  out?  Let  him  be  as  debased  and  benighted  a  savage  as  he  may, 
shut  out  from  all  communion  with  races  whom  Providence  has  placed  in 
happier  circumstances,  he  has  still  the  same  organization,  and  is  liable  to 
the  same  physiological  incidents  as  ourselves.  Like  us,  he  sees  in  his 
visions  the  fading  forms  of  landscapes,  which  are,  perhaps,  connected  with 


416  USE   OF  INVERSE   VISION. 

some  of  his  most  grateful  recollections ;  and  what  other  conclusion  can 
he  possibly  derive  from  these  unreal  pictures  than  that  they  are  the  fore- 
shadowings  of  another  land  beyond  that  in  which  his  lot  is  cast  ?  Like 
us,  he  is  visited  at  intervals  by  the  resemblances  of  those  whom  he  has 
loved  or  hated  while  they  were  alive  ;  nor  can  he  ever  be  so  brutalized  as 
not  to  discern  in  such  manifestations  suggestions  which  to  him  are  in- 
controvertible proofs  of  the  existence  and  immortality  of  the  soul.  Even 
in  the  most  refined  social  conditions  we  are  never  able  to  shake  off  the 
impression  of  these  occurrences,  and  are  perpetually  drawing  from  them 
the  same  conclusions  as  did  our  uncivilized  ancestors.  Our  more  ele- 
vated condition  of  life  in  no  respect  relieves  us  from  the  inevitable  con- 
sequences of  our  own  organization  any  more  than  it  relieves  us  from  in- 
firmities and  disease.  In  these  respects,  all  over  the  globe,  we  are  on  an 
equality.  Savage  or  civilized,  we  carry  about  within  us  a  mechanism  in- 
tended to  present  us  with  mementoes  of  the  most  solemn  facts  with  which 
we  can  be  concerned, -and  the  voice  of  history  tells  us  that  it  has  ever  been 
true  to  its  design.  It  wants  only  moments  of  repose  or  of  sickness,  when 
the  influence  of  external  things  is  diminished,  to  come  into  full  play,  and 
these  are  precisely  the  moments  when  we  are  best  prepared  for  the  truths 
it  is  going  to  suggest.  Such  a  mechanism  is  in  keeping  with  the  man- 
ner in  which  the  course  of  nature  is  fulfilled,  and  bears  in  its  very  style 
the  impress  of  invariability  of  action.  It  is  no  respecter  of  persons.  It 
neither  permits  the  haughtiest  to  be  free  from  the  monitions,  nor  leaves 
the  humblest  without  the  consolation  of  a  knowledge  of  another  life. 
Liable  to  no  mischances,  open  to  no  opportunities  of  being  tampered  with 
by  the  designing  or  interested,  requiring  no  extraneous  human  agency  for 
its  effect,  but  always  present  with  each  man,  wherever  he  may  go,  it 
marvelously  extracts  from  vestiges  of  the  impressions  of  the  past  over- 
whelming proofs  of  the  reality  of  the  future,  and,  gathering  its  power  from 
what  would  seem  to  be  a  most  unlikely  source,  it  insensibly  leads  us, 
no  matter  who  or  where  we  may  be,  to  a  profound  belief  in  the  immortal 
and  imperishable,  from  phantoms  which  have  scarcely  made  their  appear- 
ance before  they  are  ready  to  vanish  away. 

It  is  scarcely  necessary  for  me  to  do  more  than  barely  refer  to  the  as- 
sertions of  those  who  would  have  it  believed  that  they  look  upon  all 
these  appearances  as  fictions  and  deliberate  impostures.  What  is  to  be- 
come of  all  history  if  such  a  doctrine  could  be  maintained  ?  Human  ev- 
idence must  be  regarded  as  utterly  worthless.  Moreover,  no  one  denies 
the  existence  of  dreams,  and  the  phenomena  we  have  been  here  treating 
of  are  philosophically  of  the  same  order. 


OF  TOUCH.  417 


CHAPTER  XXII. 

OF  TOUCH,  AND  THE  DETERMINATION  OF  PRESSURES  AND  TEMPERA- 
TURES. 

Functions  of  the  tactile  Mechanism:  its  Structure. — Regions  of  different  Sensitiveness. —  Compar- 
ative Physiology  of  Touch. — Estimate  of  physical  Qualities. 
Perception  of  Temperature. — Subjective  Sensations  of  Temperature. 

THE  tactile  organ  is  the  skin,  or  some  part,  modification,  or  append- 
age of  it.     The  general  functions  of  the  skin  have  Ibeen  al-  Functions  of 
ready  described.     It  remains  to  speak  of  it  in  connection  with  mecifanism 
the  sense  of  touch. 

An  impression  has  long  prevailed  among  physiologists  that  this  sense 
should  be  considered  as  offering  several  subdivisions.  Thus,  for  in- 
stance, we  have  a  consciousness  of  the  general  condition  of  the  muscular 
system — muscular  sense,  as  it  might  be  termed — and  this,  in  some  cases, 
is  exquisitely  perfect,  as  may  be  gathered  from  what  has  been  said  re- 
garding the  tensor  tympani  and  stapedius  muscles  in  the  chapter  on 
hearing.  Distinct  from  this  is  our  appreciation  of  pain  or  pleasure,  and 
so  also  our  estimation  of  temperatures.  Adelon  has  indeed  maintained 
that  the  cognizance  of  temperatures  is  the  primary  or  chief  function  of 
this  sense.  It  will  be  sufficient,  however,  for  our  purpose,  leaving  out 
these  minor  subdivisions,  to  direct  our  attention  to  the  more  important, 
and  to  consider  the  tactile  organ  as  devoted  to  two  uses :  1st,  the  appre- 
ciation of  pressures  ;  2d,  of  temperatures.  Pressures  doubtless  act  upon 
the  skin  in  a  purely  mechanical  way ;  temperatures  operate  by  inducing 
a  variation  in  the  rate  of  waste  and  nutrition.  .At  a  certain  point,  even 
this  distinction  ceases,  for  pressures,  when  they  reach  a  sufficient  intensi- 
ty, interfere  with  the  supply  of  arterial  blood  or  the  removal  of  venous, 
and  thereby  change  the  rate  of  nutrition  and  waste,  acting,  as  far  as 
this  goes,  in  a  manner  not  unlike  that  of  the  variations  of  temperature. 

In  man,  the  skin  possesses  tactility  to  a  different  degree  in  different 
regions.     On  the  tips  of  the  fingers  and  on  the  lips  the  sen-  Re  ional  dif 
sory  perception  is  most  acute,  while  it  is  at  a  minimum  on  ference  in  tac- 
the  trunk  and  thigh.     In  other  mammals,  which  are  covered  tx  lty' 
with  hair  or  wool,  the  sense  of  touch  is  much  more  restricted.     Its 
proper  organ  is  to  be  regarded  as  arising  from  a  concentration  of  general 
sensibility  of  the  skin  upon  a  special  construction,  the  papillary  body, 
as  it  is  termed.     The  organs  of  vision  and  hearing  consist  essentially  of 

DD 


418  THE    ORGAN    OF   TOUCH. 

two  portions,  a  receiving  and  a  nervous,  the  former  being  constructed  on 
the  principles  of  optics  in  the  one  case,  and  of  acoustics  in  the  other.  A 
similar  doubleness  of  structure  may  be  recognized  in  the  instance  now 
before  us,  though  with  a  difference  of  effect,  for  in  those  cases  the  outer 
or  receiving  organ  is  for  the  purpose  of  more  powerfully  concentrating 
the  influence  received,  but  in  touch  it  is  the  reverse.  The  office  of  the 
cuticle,  which  covers  over  the  true  skin,  is  to  render  it  less  sensitive  to 
external  impressions,  and  for  this  reason,  therefore,  it  varies  in  thick- 
ness in  different  regions,  being  less  developed  on  those  portions  that  are 
more  particularly  devoted  to  tactile  sensibility.  Considering  the  hand, 
Structure  of  or-  or»  perhaps,  more  correctly,  the  tips  of  the  ringers,  as  being 
gan  of  touch,  chiefly  devoted  to  the  purposes  of  touch,  no  construction 
could  be  conceived  of  better  adapted  to  that  end.  Placed  at  the  extrem- 
ity of  the  arm,  a  lever  which  is  jointed  at  its  middle,  the  elbow,  and  the 
fore  part  of  which  has  a  motion  of  partial  rotation,  pronation,  and  supina- 
tion  upon  its  own  axis,  the  hand  being  carried  so  that  its  palm  presents 
upward  or  downward,  or  in  any  of  the  intermediate  positions  included  in 
the  half-circular  motion — -jointed  again  by  the  bones  of  the  wrist,  so  as 
to  obtain  a  hinge-like  movement,  the  hand  may  be  flexed  or  extended 
almost  180  degrees  upon  the  forearm.  Its  bony  structure,  subdivided 
into  suitable  pieces,  is  clothed  with  a  multitude  of  muscles  or  their  ten- 
dons. In  the  fingers  and  thumb  the  structure  breaks  up  into  five  sep- 
arate pieces,  possessed  of  an  incredible  firmness  when  we  consider  the 
numberless  motions  which  can  be  accomplished.  The  position  and  ar- 
ticulation of  the  thumb,  which  enables  it  to  set  itself  in  opposition  to 
the  other  four  digits,  a  feature  which  constitutes  a  hand,  properly  speak- 
ing, gives  the  power  of  grasping  things  perfectly,  and  makes  the  whole 
organ  a  perfect  mechanism  of  prehension.  The  papillary  structure,  de- 
veloped in  its  utmost  refinement  on  the  tips  of  the  fingers,  and  fortified 
behind  by  the  nails,  which  present  moderate  resistance  to  pressures,  com- 
pletes this  contrivance,  which,  from  its  perfect  adaptation  to 'the 'uses  to 
which  it  is  devoted,  its  power,  its  delicacy,  and  the  infinite  movements 
which  it  can  accomplish,  is  not  surpassed  as  an  example  of  the  adapta- 
tion of  means  for  the  accomplishment  of  an  end  by  any  other  structure 
of  the  body.  There  have  been  authors  who  have  asserted  that  the  su- 
periority of  man  over  other  animals  may  be  entirely  accounted  for  by  his 
possession  of  a  hand — a  statement  which,  though  it  can  not  be  main- 
tained in  its  generality,  is  yet  a  very  good  proof  of  the  appreciation  in 
which  this  wonderful  instrument  is  held  by  those  who  have  studied  its 
construction  and  functions  most  closely. 

Between  the  indications  that  have  to  be  dealt  with  by  the  hand  as 
an  organ  of  touch,  and  those  dealt  with  by  the  eye  and  ear,  there  is  an 
essential,  difference.  The  eye,  for  example,  receives  the  pictures  of  ex- 


EXAMINATION  OF  SOLIDITY.  419 

ternal  objects  upon  a  surface,  but  the  hand  examines  the  so-  Examination 
lidity  of  bodies.  The  former  is  occupied  with  length  and  of  solidity  by 
breadth ;  the  latter  with  all  three  dimensions,  length,  breadth,  the  hand' 
and  thickness  conjointly.  Our  notions  of  solidity  are  to  no  little  extent 
obtained  in  this  way,  as  was  proved  in  the  case  of  Cheselden's  patient, 
who  had  been  blind  from  birth,  and  to  whom  vision  was  given  by  a  suc- 
cessful operation  for  cataract,  and  still  more  recently  by  a  similar  case 
of  Franz.  In  this  instance,  "a  solid  cube  and  a  sphere,  each  of  four 
inches  diameter,  were  placed  before  the  patient,  at  the  distance  of  three 
feet,  and  on  a  level  with  the  eye.  After  attentively  examining  these 
bodies,  he  said  he  saw  a  quadrangular  and  a  circular  figure,  and,  after 
some  consideration,  he  pronounced  the  one  a  square  and  the  other  a  disk. 
His  eye  being  then  closed,  the  cube  was  taken  away,  and  a  disk  of  equal 
size  substituted,  and  placed  next  to  the  sphere.  On  again  opening  his 
eye,  he  observed  no  difference  in  these  objects,  but  regarded  them  both 
as  disks.  The  solid  cube  was  now  placed  in  a  somewhat  oblique  posi- 
tion before  the  eye,  and,  close  beside  it,  a  figure  cut  out  of  pasteboard, 
representing  a  plain  outline  prospect  of  the  cube  when  in  this  position : 
both  objects  he  took  to  be  somewhat  like  a  flat  quadrate.  A  pyramid 
placed  before  him,  with  one  of  its  sides  turned  toward  his  eye,  he  saw  as 
a  plain  triangle.  This  object  was  now  turned  a  little,  so  as  to  present 
two  of  its  sides  to  view,  but  rather  more  of  one  side  than  of  the  other : 
after  considering  and  examining  it  for  a  long  time,  he  said  that  this  was 
a  very  extraordinary  figure  ;  it  was  neither  a  triangle,  nor  a  quadrangle, 
nor  a  circle — he  had  no  idea  of  it,  and  could  not  describe  it :  'in  fact,' 
said  he,  'I  must  give  it  up.'  An  example  of  the  close  association  which 
exists  between  the  sense  of  touch  and  that  of  sight,  in  enabling  the  mind 
to  form  a  correct  idea  of  an  object,  is  afforded  in  the  statement  of  this 
patient,  that,  although  by  the  sense  of  sight  he  could  detect  a  difference 
in  the  cube  and  sphere,  and  perceive  that  they  were  not  drawings,  yet 
he  could  not  form  from  them  the  idea  of  a  square  and  a  disk  until  he 
perceived  a  sensation  of  what  he  saw  in  the  points  of  his  fingers  as  if  he 
really  touched  the  objects/  When  he  took  the  sphere,  cube,  and  pyra- 
mid into  his  hand,  he  was  astonished  that  he  had  not  recognized  them  asf 
such  by  sight,  being  well  acquainted  with  them  by  touch." 

The  mechanism  for  touch,  as  distinguished  from  the  general  dermoid 
sensibility,  is  the  papilla,  which  may  be  described  as  conical  Structure  of 
eminences  on  the  cutis,  at  once  solid  and  flexible,  sometimes  papillae  of 
clavate  in  form,  and  sometimes  having  numerous  points.    They 
are  about  the  TJ^  of  an  inch  in  height,  and  the  -% J^  of  an  inch  in  diam- 
eter at  their  base,  these  dimensions  varying,  however,  very  greatly  with 
the  situation.     They  contain  a  loop  of  blood-vessels  and  a  twig  of  a 
sensory  nerve,  for  all  the  centripetal  nerves,  with  the  exception  of  those 


420  THE   PACINIAN   BODIES. 

devoted  to  the  special  senses,  may  be  regarded  as  concerned  in  this  func- 
tion. The  papilla?  contain  an  elastic  substance — axile  body,  as  it  is  term- 
ed  which  serves  to  heighten  the  sense,  and  the  yielding  structure  of  the 

skin  aids  in  the  same  effect.    The  papilla?  are  covered  over  with  the  cuti- 
cle, through  which,  therefore,  all  ***• 204- 
action  on  them  must  take  place. 

Fig.  203. 


Simple  papillae,  magnified  35  diameters.  Compound  papillae,  magnified  60  diameters. 

Fig.  203  (Todd  and  Bowman)  represents  simple  papilla?  of  the  palm, 
the  cuticle  having  been  detached.  Fig.  204  (Kolliker),  compound  papil- 
ke,  with  two,  three,  or  four  points :  a,  base  of  a  papilla ;  #,  £,  £,  separate 
processes ;  c,  c9  c,  processes  of  papilla?  whose  bases  are  not  visible. 

The  mode  in  which  the  nerve  fibre  terminates  in  the  papilla  is  as  yet 
The  Pacinian  doubtful,  some  asserting  that  it  is  arranged  as  a  returning 
bodies.  loop,  and  some  that  it  is  by  a  pointed  extremity.  This  lat- 

ter mode  is  thought  to  be  illustrated  by  the  structure  of  the  bodies  term- 
ed Pacinian,  which  are  ovoid  in  form,  -^  to  -^  of  an  inch  in  length,  -^  to 
-g1^  in  breadth,  and  attached  by  a  pedicle  to  many  of  the  cerebro-spinal 
and  sympathetic  nerve  branches.  Each  consists  of  many  concentric 
membranous  layers,  arranged  like  the  coats  of  an  onion,  the  interior  ones 
closer  than  the  exterior.  They  have  a  central  cavity,  distended  by  a 
fluid,  which  also  intervenes  between  the  coats.  Across  this  cavity,  and 
occupying  exactly  its  axis,  a  nerve  fibre,  which  has  cast  off  its  white 
sheath,  passes,  terminating  at  the  other  end  either  in  branches  or  a  knob. 
The  use  of  these  bodies  is  wholly  unknown,  and  even  their  structure  is 
doubtful,  the  existence  of  the  central  liquid  referred  to  being  denied  by 
some  anatomists. 

The  sensitiveness  of  a  part  is  in  proportion  to  the  number  of  papilla? 
The  sensitive-  **  contams-  Tables  have  been  constructed  setting  forth  the 
ness  of  differ-  relations  of  different  regions,  as  determined  by  placing  a  pair 
regions.  Q£  compasseSj  tjie  p0ints  Of  which  were  covered  with  cork,  on 
the  parts  to  be  tried,  the  eyes  being  shut,  and  closing  the  compasses  un- 
til the  pieces  of  cork  could  no  longer  be  distinguished  as  separate.  It 
appears  that  this  will  take  place  on  the  tip  of  the  tongue  when  the  points 
are  the  -^  of  an  inch  apart ;  on  the  tip  of  the  third  phalanx,  at  the  -fa 
of  an  inch ;  on  the  lips,  the  one  sixth  of  an  inch ;  tip  of  the  great  toe, 
half  an  inch ;  the  lower  part  of  the  occiput,  1  inch ;  and  on  the  middle 
of  the  thigh,  2  J  inches. 

No  part  of  the  skin  is  entirely  devoid  of  sensitiveness,  as  Kolliker  has 


NEEVES  OF  THE   PAPILLA.  421 

shown  by  examinations  with  a  fine  needle.      At  first  he  ,, 

»  Jbvery  part  of 

thought  he  had  found  some  places  which  were  quite  insensi-  the  skin  is  sen- 
ble,  while  in  others  the  slightest  touch  produced  sensation ;  8Itlve* 
but  on  carrying  the  investigation  farther,  it  appeared  that  the  very  same 
place  was  sometimes  sensible  and  sometimes  not,  so  that  finally  he  came 
to  the  conclusion  that  the  very  smallest  portions  of  the  skin  are  sensi- 
tive. But  since,  even  in  the  palm  of  the  hand,  the  papillae  containing 
nerves  are  widely  dispersed,  and  in  other  places  occur  but  rarely,  or 
even  not  at  all,  he  infers  that  it  is  necessary  to  assume  the  existence  of 
non-medullated  fibres  in  all  the  papillae,  or  to  have  recourse  to  the  nerv- 
ous plexus  at  their  base,  since  he  believes  it  is  not  possible  to  demon- 
strate nerves  in  eveiy  one  of  those  bodies. 

The  nerves  supplying  the  papillae  may  perhaps  be  said  to  ascend 
through  the  cutis,  continually  branching,  and  forming  eventu-  papillary 
ally  terminal  plexuses.  The  primitive  tubules  themselves  di-  nerves. 
viding  at  an  acute  angle  into  two,  and  entering  the  papillae,  they  are 
united  at  their  extremities  in  a  loop.  Of  course,  this  construction  in- 
volves the  fact  that  they  have  freed  themselves  from  the  white  substance 
of  Schwann.  The  impression  made  on  these  exposed  nervous  fibrils  is 
by  many  regarded  as  of  a  purely  mechanical  kind.  They  may  be  affect- 
ed not  merely  by  vertical  pressures,  but  likewise  by  those  exerted  in  the 
direction  of  the  plane  of  the  skin,  and  this  accounts  for  tactile  sensation 
on  portions  of  that  surface  which  are  either  sparsely  or  not  at  all  sup- 
plied with  nerve  fibrils.  To  this  effect  the  unyielding  and  horny  texture 
of  the  cuticle  doubtless  contributes. 

No  papillae  are  found  in  invertebrate  animals.  Among  vertebrates 
they  are  variously  disposed.  In  lizards  they  occur  under  TQ^  jn  other 
the  toes  ;  in  the  chameleon,  and  some  of  the  ant-eaters,  which  vertebrates. 
use  their  tails  for  tactile  purposes,  they  are  found  upon  that  organ.  In 
the  spring  season  of  the  year  they  are  temporarily  developed  on  the  thumb 
of  the  frog.  Among  birds  they  are  found  upon  the  toes,  or,  if  web-foot- 
ed, upon  the  web  ;  in  the  mole  on  the  tip  of  the  snout.  In  the  tapir  and 
elephant  they  occur  upon  the  trunk ;  among  the  quadrumana,  on  the 
hands  and  feet,  and  in  some  also  upon  the  tail.  The  whiskers  of  the  cat, 
the  rat,  the  rabbit,  may  be  regarded  as  appendages  to  the  tactile  organs, 
enabling  them  to  find  their  way  through  narrow  passages  in  the  dark. 
Among  articulata  the  antennae  have  doubtless,  with  their  other  functions, 
a  similar  use.  Men  who  have  become  blind  often  guide  their  steps  by 
means  of  a  stick,  judging  from  the  sensations  which  its  contact  with  sur- 
rounding bodies  imparts  to  the  hand :  it  is  in  all  respects  a  temporary 
antenna. 

Our  estimates  of  the  hardness  and  softness,  roughness  and  smoothness 
of  bodies,  is  primarily  dependent  on  indications  derived  from  the  sense 


422  FEELING   AND   TOUCHING. 

Estimate  of  °^  toucn'  We  should  make  a  distinction,  however,  with 
physical  quail-  Magendie,  between  feeling  and  touching,  the  former  being 
essentially  passive,  the  latter  active;  and  though  we  usu- 


suPPose  that,  °^  a^  our  senses,  touch  is  the  most  reli- 
and  touching,  able,  it  often  conveys  to  the  mind  illusory  impressions,  as, 
for  instance,  in  the  well-known  experiment  of  Aristotle,  when  the  tips  of. 
the  fingers  are  crossed  over  each  other,  and  a  pea  rolled  beneath  them,  it 
seems  as  if  there  were  two  peas,  one  under  each  finger.  The  indications 
of  touch  are  generally  more  correct  than  those  of  feeling.  Thus,  if  we 
close  our  eyes,  and  another  person  moves  the  tip  of  our  finger  over  an 
unknown  surface,  he  can  completely  deceive  us  by  duly  varying  the  press- 
ure, and  make  us  believe  that  it  is  concave  or  convex,  whereas  it  may  be 
flat  ;  but  if  we  pass  our  fingers  over  the  surface  ourselves,  we  very  quick- 
ly come  to  a  true  conclusion,  because  now  we  are  conscious  of  the  exer- 
tion of  muscular  power  ;  and  from  what  has  been  said  respecting  hearing, 
we  may  infer  how  delicate  our  estimate  of  muscular  exertion  is.  The 
former  is  therefore  an  example  of  feeling,  the  latter  .of  touch. 

Connected  with  this  distinction  are  the  singular  phenomena  of  tick- 
ling ;  the  regions  most  readily  affected  by  this  are  those  of  low 
tactile  sensibility.  A  person  can  not  tickle  himself,  though  it 
is  said  that  cases  are  upon  record  in  which  one  has  been  tickled  to  death 
by  another.  As  in  the  other  cases,  the  mind  can  direct  attention  exclu- 
sively, for  the  time  being,  to  some  one  indication  of  touch,  which,  though 
it  may  be  apparently  insignificant  in  itself,  becomes,  after  a  while,  per- 
fectly intolerable,  as  the  pressure  of  a  hair,  a  gentle  draught,  or  the  fall- 
Remains  of  im-  mg  °f  water,  drop  by  drop,  on  the  top  of  the  head  ;  and,  as 
pressious.  with  them,  an  impression  which  is  made  does  not  instanta- 
neously disappear,  but  will  sometimes  continue  for  quite  a  considerable 
time.  A  ring  or  other  article  that  has  been  long  worn  will  leave  a  sen- 
sation, though  it  may  have  been  removed. 

Besides  affording  an  estimate  of  external  pressures,  the  sensory  organ 
enables  us  to  discover  variations  of  temperature.  It  may  therefore  be 
thus  effected  by  bodies  upon  contact  or  by  bodies  at  a  distance  ;  and 
Perception  of  though  we  usually  confound  the  two  indications  together, 
temperature  there  is,  in  reality,  a  distinction  between  them  ;  thus,  in  cer- 

distmctfrom          .  .  J  ,.,.,..  _    ,  „ 

that  of  press-  tain  conditions  of  paralysis,  the  indications  of  the  contact  of 
bodies  may  remain,  but  those  of  heat  and  cold  may  have  to- 
tally disappeared.  On  examining  a  surface  from  which  the  skin  has 
been  removed,  it  does  not  appear  capable  of  distinguishing  hot  from  cold 
bodies,  but  only  communicates  to  the  mind  an  indefinite  sensation  of 
Ideas  of  heat  pain  ;  nor  can  we  create  sensations  of  heat  or  cold  by  any  ir- 
nof  arise  Trd-  ritati(>n  ^  the  nerves.  The  measure  of  temperature  by  the 
ficiaiiy.  agency  of  the  skin  is  very  far  from  being  exact,  as  has  been 


OF   SMELLING.  423 

proved  by  the  simple  experiment  of  dipping  the  finger  into  very  warm 
water,  and  then  the  whole  hand  into  water  many  degrees  cooler.     The 
increased  extent  of  surface  seems  to  overcompensate  for  the  Dece  tions 
lower  temperature,  and  we  come  to  the  erroneous  conclusion  the  sense  of 
that  the  cooler  specimen  is  the  warmer  of  the  two  samples. 

As  sounds  may  be  heard  which  have  no  reality,  but  merely  originate 
in  the  brain,  or  spectral  illusions  may  be  seen,  so  the  sense  Subjective  sen- 
of  touch  is  subject  to  similar  hallucinations,  as  a  sensation 
of  pressure  or  weight,  or  the  crawling  of  insects  on  the  skin  ;  ture. 
and  though  we  can  not,  by  artificial  irritation  of  the  nerves,  give  rise  to 
impressions  of  heat  and  cold,  those  effects  very  frequently  occur  in  this 
interior  or  subjective  way. 


CHAPTEE  XXIII. 

OF  SMELLING,  AND  THE  MEANS  OF  DISTINGUISHING  GASEOUS  AND  VA- 
POEOUS  SUBSTANCES. 

Structure  of  the  Organ  of  Smell. — Its  proper  Instrument  the  First  Pair  of  Nerves. — Limited  Re- 
gion of  Smell. —  Conditions  of  its  perfect  Action. — Duration  of  Odors. — TJieir  Localization. — 
Subjective  Odors. 

BY  the  sense  of  smell  we  are  able  to  distinguish  many  gaseous  and 
vaporous  substances  from  one  another.  They  enter  the  nos-  gensc  of  gmell 
trils  with  the  respiratory  current,  and  are  brought  in  con-  for  gases  and 
tact  with  the  olfactory  or  Schneiderian  membrane.  Though  vaP°rs- 
received  at  first  in  the  elastic  state,  they  become  dissolved  in  the  mucus 
which  moistens  that  membrane.  It  does  not  follow,  however,  that  all 
vaporous  substances  give  rise  to  the  perception  of  an  odor ;  for  example, 
water  itself  communicates  no  sensation  whatever.  Again,  there  are  other 
bodies,  as,  for  instance,  musk,  which  yield  an  odor  far  more  Deiicacj-oftMs 
powerful  than  corresponds  to  their  loss  of  weight.  Thus  it  perception, 
is  said  that.that  substance  may  be  exposed  for  years  in  an  apartment,  dif- 
fusing all  the  time  its  penetrating  emanations,  and  yet  not  becoming 
lighter.  Such  statements  are,  however,  on  their  face,  exaggerations. 
There  can  be  no  doubt  that  the  olfactory  organs  detect  extremely  minute 
portions  of  matter.  In  most  cases,  elevation  of  the  temperature  of  a 
body  increases  its  odorous  effect. 

The  primary  uses  of  the  function  of  smell  are  for  a  discrimination  of 
the  qualities  of  food,  or  its  condition,  and  also  for  enabling 

,      .,,  p     ••!•.  -i     «,     ic     -,T  T          Uses  of  smell. 

an  animal  with  greater  lacility  to  provide  it  sen  with  supplies. 
Hence  the  development  of  this  structure  takes  place  in  the  utmost  per- 
fection among  the  carnivora,  which  often  depend  almost  exclusively  upon 


424  THE   OLFACTOKY   ORGAN. 

this  faculty  for  the  pursuit  of  their  prey.  But  even  in  the  herbivora  it 
is  well  marked,  and  furnishes  them,  though  less  exactly,  similar  indica- 
tions. In  man,  though  this  sense  is  less  acutely  developed,  it  applies 
itself  to  a  greater  variety  of  objects,  and  doubtless  enables  him  to  appre- 
ciate differences  among  odors  in  a  more  correct  manner  than  in  the  case 
of  the  lower  animals. 

The  general  principle  involved  in  the  construction  of  the  organ  of  smell 
Mechanism  of  *s  to  exPose  an  extensive  and  constantly  moistened  surface 
the  olfactory  to  the  air  brought  in  by  the  respiratory  current.  Of  course, 
other  things  being  equal,  the  larger  the  surface,  the  more  per- 
fect the  sense.  The  object  of  gaining  a  great  extent  of  superficial  ex- 
posure under  a  relatively  small  volume  is  accomplished  by  spreading 
the  sensitive  mucous  membrane  on  projections  or  shelves,  which  also 
serve  the  purpose  of  intercepting  the  incoming  current  of  air.  It  is  in 
reptiles  and  birds  that  turbinated  processes  first  make  their  appearance. 
In  air-breathing  animals,  the  organ  of  smell  is  essentially  an  appendix 
to  the  respiratory  mechanism,  its  action  depending  entirely  upon  the 
play  thereof.  But,  though  the  material  submitted  to  the  olfactory  mem- 
brane in  this  manner  is  presented  in  the  vaporous  or  gaseous  state,  it  is 
intermediately  dissolved,  as  has  been  stated,  in  the  liquid  mucus  which 
covers  that  membrane,  before  it  can  affect  the  ramifications  of  the  olfac- 
tory nerve. 

The  nose,  thus  constituting  the  commencement  of  the  respiratory 
tract,  forms  a  characteristic  feature  of  the  countenance.  It  is  composed 
in  part  of  bones  and  in  part  of  cartilages,  covered  over  with  muscles  and 
integument.  Its  five  cartilages  give  to  it  shape  in  its  inferior  portion, 
and,  by  their  elasticity,  enable  it  to  resist  external  injury.  The  whole 
surface  of  the  nasal  cavities  is  covered  over  with  mucous  membrane,  to 
which  the  names  of  pituitary  or  Schneiderian  membrane  have  been  given. 
This  mucous  membrane  likewise  extends  into  the  maxillary  antrum, 
ethmoid,  and  sphenoid  cells,  or  sinuses  which  are  adjacent,  and  open  into 
the  same  nasal  cavity.  The  Schneiderian  membrane  is  highly  vascular, 
and  receives  its  nervous  supply  from  the  nasal  branches  of  the  fifth 
pair,  which  give  it  common  sensibility,  but  its  olfactory  function  de- 
205.  Fig.  206.  pends  on  the  distribution  which  a 

certain  portion  of  it  receives  from 
the  first,  or  olfactory  nerve. 

Fig.  205  illustrates  the  distribu- 
tion of  the  olfactory  nerve  on  the 
septum  of  the  nose.     Fig.  206  is 
its  distribution  on  the  outer  wall  of 
the  nasal  fossa. 

That  the  function  of  the  first  pair  of  nerves  is  olfactory  is  proved  by 


THE   OLFACTORY  NERVES.  425 

many  facts.     Animals  in  which  these  nerves  have  been  di-  Functionofthe 
vided  are  no  longer  affected  by  odors  of  any  kind,  and,  gen-  first  pair  of 
erally  speaking,  the  greater  the  development  of  these  nerves,  nerves- 
the  acuter  is  the  sense  of  smell.     In  persons  in  whom  this  sense  has 
been  defective  or  totally  absent,  or  in  those  who  have  been  troubled  with 
unpleasant  odors  of  a  subjective  kind,  post-mortem  examinations  have 
shown  a  corresponding  absence  or  lesion  of  these  nerves. 

In  man,  the  proper  olfactory  organ  is  formed  by  the  distribution  of  the 
olfactory,  or  first'  pair  of  nerves,  on  the  mucous  membrane  which  covers 
the  upper  part  of  the  nose,  the  internal  set  of  filaments  being  disposed 
on  that  of  the  septum,  the  external  on  that  of  the  superior  and  middle 
spongy  bones.  The  membrane  is  very  vascular,  and  covered  with  a  thick, 
pulpy  epithelium.  The  filaments  distributed  to  it  have  lost  the  white 
substance  of  Schwann.  It  is  those  parts  alone  to  which  these  filaments 
are  distributed  which  possess  the  sense  of  smell,  the  adjacent  cavities, 
as,  for  example,  the  frontal  sinuses,  not  participating  in  the  function,  as 
has  been  proved  by  the  injecting  of  the  vapor  of  camphor  or  other  odo- 
riferous bodies  into  them.  It  seems  to  be  necessary  for  the  vaporous  or 
gaseous  substances  to  be  dissolved  in  the  moisture  which  covers  the  ol- 
factory membrane  in  order  to  their  exerting  a  proper  effect.  If,  by 
chance,  the  membrane  is  too  dry,  the  sense  of  smell  is  temporarily  lost, 
and  the  same  likewise  occurs  if  it  be  unusually  moist. 

From  the  mode  of  distribution  of  the  olfactory  nerve,  it  follows  that* 
the  sense  of  smelling  is  restricted  to  the  upper  portion  of  Limited  re  ion 
the  nasal  cavity ;  and,  for  this  reason,  when  we  desire  to  de-  for  the  sense  of 
tect  odors  with  unusual  precision,  the  air  is  drawn  violently  smell> 
into  that  region  by  sniffing.     On  the  contrary,  we  avoid  the  perception 
of  odors  by  breathing  through  the  mouth,  or,  as  the  common  Conditions  for 
phrase  is,  by  holding  the  nose.     Since  the  perfection  of  the  its  perfect  ac- 
sense  requires  that  the  olfactory  surface  shall  neither  be  too  i 
dry  nor  too  cold,  an  advantage  is  gained  by  placing  it  high  in  the  cav- 
ity, where  it  is  free  from  the  disturbing  effects  of  the  dry  air  introduced 
by  inspiration,  which  becomes  moistened  and  warm  before  it  reaches  the 
place  of  action. 

Just  as  we  make  a  distinction  between  a  musical  sound  and  a  noise, 
so  should  we  distinguish  between  an  odor  and  such  impres-  Distinction  be_ 
sions  as  arise  from  tickling,  pressures,  the  use  of  snuff,  mus-  tween  odors 
tard,  pepper,  and  pungent  bodies,  for  these  act  as  mere  irri- 
tants, and  many  of  them  can  produce  analogous  effects  on  other  portions 
of  the  surface  of  the  skin.     Odors  do  not  give  rise  to  the  impressions  of 
pain,  and,  indeed,  the  nervous  mechanism  having  charge  of  the  action  is 
totally  different  in  the  two  cases.     Odors  operate,  as  we  have  said,  upon 
the  olfactory  nerve,  but  these  other  impressions  are  made  upon  the  nasal 


426  DURATION  AND  LOCALIZATION  OF  ODORS. 

supplies  from  the  fifth  pair.  The  upper  part  of  the  nasal  cavity  is  there- 
fore devoted  to  the  proper  sense  of  smell,  the  lower  portion  to  general 
sensation. 

In  one  respect  there  is  a  striking  difference  between  this  sense  and 
Duration  of  vision  and  hearing.  We  can  perceive  many  luminous  im- 
odors.  pressions  at  the  same  time,  or  hear  many  sounds  in  rapid  suc- 
cession ;  but  not  so  with  odors.  We  can  smell  only  one  thing  at  a  time, 
or,  at  all  events,  the  impression  remains  long  upon  the  olfactory  appara- 
tus, perhaps  because  the  odoriferous  substance  remains  dissolved  in  the 
attached  moisture.  The  identification  of  substances  by  their  odor  nec- 
essarily implies  a  resort  to  recollection  or  memory,  and  sometimes  we 
have  to  apply  the  fragrant  object  again  and  again  to  the  nose,  before  we 
can  recall  with  satisfactory  precision  its  name. 

In  the  lower  animals  the  sense  of  smell  is  probably  localized  in  some 
parts  of  the  skin ;  many  of  them  display  instincts  which  seem 
anatomy  of    to  imply  the  possession  of  such  a  sense.     Insects  also,  by 
smell,  are  often  led  to  their  food  or  to  one  another. 

The  variable  current  of  air  introduced  by  respiration  compensates  in 
some  degree  for  the  want  of  mobility  of  the  nose,  which  may  be  regard- 
ed, in  air-breathing  vertebrated  animals,  as  consisting  of  a  diverticulum 
from  the  respiratory  passages.  In  fishes,  however,  the  olfactory  cavity  is 
not  connected  with  the  respiratory  passages :  there  are  no  posterior  nares. 
'The  circumstance  of  their  living  under  water  disables  them  from  appreci- 
ating the  odorous  peculiarities  of  gases  and  vapors.  In  the  whale  the  or- 
gan is  altogether  absent,  being  replaced  by  the  mechanism  for  receiving 
air  and  blowing  out  water.  In  other  tribes  the  acuteness  of  the  sense 
is  in  proportion  to  the  development  of  the  olfactory  ganglia :  in  reptiles 
it  is  feeble ;  in  birds,  more  developed ;  in  carnivorous  animals,  still  more. 
But  here  again  it  exhibits  a  special  restriction,  since  there  is  reason  for 
supposing  that  carnivorous  animals  are  insensible  to  the  perfume  of  flow- 
ers, while  herbivorous  ones  distinguish  them  perfectly.  In  man,  as  we 
have  said,  the  sense  is  less  developed,  but  it  has  a  wider  range. 

The  localization  of  odors  is  effected  in  a  much  less  perfect  manner  than 
Localization  the  localization  of  sounds.  The  principle  by  which  it  is  ac- 
of  odors.  complished  is  obviously  that  of  determining  the  direction,  of 
maximum  intensity,  and  this  involves  necessarily  the  constant  exercise 
of  memory  and  comparison.  The  surprising  manner  in  which  this  can 
be  accomplished  by  animals  whose  sense  of  smell  is  acute,  as,  for  exam- 
ple, by  the  dog,  is  extremely  interesting.  From  the  different  manner  in 
which  various  odors  affect  different  individuals,  there  is  no  general  stand- 
ard of  comparison  to  which  they  may  be  referred,  as  there  is  in  the  case 
of  colors  and  of  sound.  Scents  which  may  be  highly  disagreeable  to  one 
are  acceptable  to  another  person.  By  constant  exposure,  the  faculty  may 


OP  TASTE.  427 

become  so  benumbed  as  to  be  unable  to  distinguish  some  altogether. 
Thus  Turner  found  "that  the  flower -of  the  iris  persica  was  Various  effects 
pronounced  of  pleasant  odor  by  forty-one  out  of  fifty-four  of  odorous  im- 
persons,  by  four  to  have  little  scent,  and  by  one  to  be  ill-  Prtessions- 
scented.  Of  thirty  persons,  twenty-three  held  the  anemone  nemorosa 
agreeable  in  its  perfume,  and  seven  did  not  think  that  it  smelled  at  all." 
Diseases  of  the  central  organs  will  sometimes  give  rise  to  the  percep- 
tion of  subjective  odors,  just  as  they  do  to  spectral  illusions  or  subjective 
sounds  in  the  ears.  odors. 


CHAPTER  XXIV. 

OF  TASTE. 

Conditions  for  Taste. — Structure  and  Functions  of  the  Tongue. —  Tactile  and  Gustative  Regions 
of  the  Tongue. —  Complementary  Tastes. — Subjective  Tastes. 

THOUGH  the  function  is  participated  in  by  other  portions  of  the  oral 
cavity,  the  tongue  is  to  be  regarded  as  the  organ  of  taste.  Conditions  for 
The  physical  conditions  under  which  savors  are  perceived  is  taste- 
that  the  substance  shall  be  presented  in  solution  in  water,  or,  at  all 
events,  in  the  saliva.  From  vision,  hearing,  and  smell,  the  sense  of  taste 
differs  in  the  circumstance  that  it  requires  the  contact  of  the  acting  body; 
and,  to  a  certain  extent,  the  same  distinction  which  has  been  made  re- 
garding such  substances  as  can  act  on  the  olfactory  mechanism  might 
also  be  made  here ;  that  is  to  say,  that  there  are  two  classes  of  agents 
which  affect  the  organ — those  which  produce  a  mere  pungent  sensation, 
and  those  which  excite  savors,  properly  speaking,  for  the  irritations  and 
former  will  frequently  give  rise  to  specific  action  when  ap-  savors- 
plied  to  other  portions  of  the  surface  of  the  skin. 

Sensations  of  taste  are  very  frequently  conjoined  with  olfactory  per- 
ceptions, so  that  we  mistake  the  one  for  the  other.  There  Connection  of 
are  many  substances,  reputed  to  have  a  powerful  flavor,  ceptkmTand" 
which  become  tasteless  when  the  nose  is  held ;  and  this  re-  tastes. 
mark  applies  more  particularly  to  such  as  are  at  the  same  time  volatile 
and  soluble  in  water.  However,  irrespectively  of  this,  some  of  those 
bodies  which  produce  the  most  intense  and  permanent  impression  on  the 
organs  of  taste  do  so  merely  in  virtue  of  their  solubility,  as,  for  exam- 
ple, quinine,  which  is  a  non-volatile  body.  The  intensity  of  such  action 
depends  on  the  duration  of  contact  and  the  degree  of  exposure  of  the 
substance  to  the  tongue,  so  that  the  papilla?  may,  as  it  were,  become 
thoroughly  permeated. 


428  PAPILLA   OF  THE   TON&UE. 

The  idea  of  taste  may  arise  irrespectively  of  the  presence  of  any  actual 
substance.  A  sharp  blow  will  produce  it,  as  also  the  passage 
ent  on  acci-  of  a  feeble  voltaic  current.  It  was,  indeed,  in  this  way  that 
dental  agents.  ^  fasj.  O"bservati0n  in  galvanic  electricity  was  made.  A 
narrow  jet  of  air  directed  upon  the  tongue  causes  a  taste  resembling  that 
of  saltpetre.  If  the  tongue  be  dry  and  parched,  its  power  of  discrim- 
inating tastes  is  greatly  enfeebled,  and  the  same  thing  takes  place  if  its 
temperature  is  very  much  changed,  either  by  elevation  or  depression, 
as  by  keeping  it  for  a  short  time  in  contact  with  hot  or  very  cold  water. 

The  action  of  the  tongue,  as  the  organ  of  taste,  depends  upon  the  pa- 
„  e  pillae  which  are  on  its  surface.  These  structures  give  to  the 

Structure  of     r  ^  ...  & 

the  papiii*  of  upper  portion  of  the  tongue  its  rough  appearance.  They  are 
of  three  kinds :  1st.  The  conical  papillae,  which  are  the  most 
numerous ;  2d.  The  circumvallate  papillae,  which  are  situate  near  the 
base  of  the  organ,  and  which  are  from  -^  to  -^  of  an  inch  in  diameter, 
with  a  crater-like  depression,  round  the  edge  of  which  is  a  groove,  and 
again  a  circular  elevation;  3d.  The  fungiform  papillae,  which  are  chiefly 
on  the  sides  and  tip,  their  shape  being  conical,  the  narrow  end  of  the  cone 
being  downward.  The  epithelium  of  the  tongue  is  less  dense  over  the 
fungiform  papillae,  and  hence  their  projecting  appearance :  it  is  more  dense 
over  the  conical  papillae,  and  projects  from  them  in  processes  which  pre- 
sent an  aspect  like  that  of  hairs.  Some  of  them  contain  hair-tubes. 
Besides  these,  the  surface  of  the  tongue  presents  a  papillary  structure 
resembling  that  of  the  skin — secondary  papillae,  as  they  are  termed.  It 
is  supposed  that  the  conical  papillae  are  chiefly  organs  of  prehension ;  the 
others  are  organs  of  taste,  but  that  function  is  participated  in  by  other 
portions  of  the  surface  of  the  mouth,  as,  for  example,  the  soft  palate,  its 
arches,  and  the  tonsils. 

Fig.  207  represents  the  surface  of  the  tongue  and  the  adjacent  parts : 
#,  a,  lingual  papillae  ;  £,  b,  circumvallate  papil- 
lae, disposed  along  two  converging  lines  form- 
ing the  lingual  V;  c,  foramen  ccecum ;  d,  d^ 
fungiform  papillae  ;  e,  6,  filiform  papillae ;  /", 
fraenum  epiglottidis  ;  g,  epiglottis  ;  7z,  anterior 
pillar  of  velum  ;  i,  stylo-glossus ;  Z,  isthmus 
of  the  fauces  ;  ra,  uvula ;  n,  velum  pendulum 
palati ;  0,  hard  palate ;  p,  raphe ;  £,  £,  orifices 
of  the  excretory  ducts  of  the  palatine  glands  ; 
f,  palatine  glands,  the  mucous  membrane  be- 
ing removed ;  «,  palatine  glandules ;  £,  mu- 
cous membrane  covering  the  same  glands ;  u, 
palatine  tubercle ;  i?,  v,  section  of  the  lower 

The  tongue.  JaW. 


NERVES   OF  THE  TONGUE.  429 

The  organ  of  taste  is  placed  at  the  commencement  of  the  digestive  ca- 
nal; hence  the  characters  of  substances  may  be  examined  usesofthe 
with  deliberation  while  they  are  yet  under  the  control  of  the  sense  of  taste- 
will,  for  when  once  a  body  has  entered  the  oesophagus  it  is  swallowed  in- 
voluntarily. The  tongue,  therefore,  gives  warning  of  the  presence  of  del- 
eterious substances,  and  in  no  small  degree  excites  the  appetite  by  receiv- 
ing the  impression  of  pleasant  flavors.  The  essential  condition  under 
which  it  acts  is  a  moist  state  of  its  surface,  for  the  dry  tongue,  though  it 
enjoys  common  sensibility,  after  the  manner  of  any  portion  of  the  exter- 
nal tegument,  does  not  enjoy  taste.  One  of  the  duties  of  the  salivary 
glands  is  incidentally  to  maintain  this  moistened  condition.  To  a  cer- 
tain degree,  taste  may  be  regarded  as  a  refinement  on  touch.  It  differs 
from  vision  and  hearing  in  the  peculiarity  that  there  is  no  sin-  serves  of  the 
gle  nerve  of  special  sense  individually  devoted  to  it,  for  the  tongue, 
front  of  the  tongue  is  supplied  by  the  lingual  branch  of  the  fifth  pair, 
and  the  back  by  the  glosso-pharyngeal.  Its  entire  nervous  supply  is 
derived  from  four  different  sources:  the  lingual,  the  hypoglossal,  the 
glosso-pharyngeal,  and  the  sympathetic,  representing  therefore  special 
sensibility,  muscular  motion,  common  sensibility,  and  sympathetic  rela- 
tion. That  the  hypoglossal  is  the  nerve  of  motion,  or  muscular  nerve,  is 
proved  beyond  doubt  by  its  section,  after  which  the  motions  of  the  tongue 
are  destroyed,  but  taste. and  touch  remain.  The  individual  duty  dis- 
charged by  the  glosso-pharyngeal,  and  the  lingual  branch  of  the  fifth  pair 
respectively,  is  not  so  clearly  determined.  Section  of  the  former  is  at- 
tended with  loss  of  taste,  though  it  is  not  yet  proved  that  there  is  a  loss 
of  all  kinds  of  taste.  If  the  lingual  branch  of  the  fifth  be  divided,  com- 
mon sensation  at  the  tip  of  the  tongue  is  destroyed,  and  there  is  evidence 
that  with  this  the  appreciation  of  certain  tastes  disappears.  The  glosso- 
pharyngeal  is  distributed  to  the  circumvallate  papillae,  and  it  is  said  that 
in  some  birds  the  lingual  is  suppressed.  Upon  the  whole,  therefore,  it 
may  be  concluded  that  these  nerves  are  conjointly  engaged  in  the  sense 
of  taste,  the  glosso-pharyngeal  being  engaged  with  those  flavors  which 
affect  the  back  part  of  the  tongue,  the  lingual  with  those  which  affect 
the  tip. 

Illustrations  of  the  distribution  of  the  hypoglossal  nerve  have  already 
been  given  in  its  description,  under  the  title  of  the  twelfth  pair. 

The  surface  of  the  tongue  presents  the  tactile  and  gustative  powers  in 
an  inverse  manner.     Examined  by  the  method  described  in   Tactile  and 
the  chapter  on  touch,  the  compasses  must  be  opened  to  a  great  l^*1^  the" 
extent,  as  we  pass  from  the  tip  toward  the  back  of  the  tongue,    tongue. 
in  order  that  a  double  impression  may  be  perceived.     This  condition  ap- 
pears to  be  in  accordance  with  the  requirements  of  the  organ,  common 
tactile  sensibility  being  most  necessary  at  its  outer  extremity,  and  this 


430  COMPLEMENTARY   AND    SUBJECTIVE   TASTES. 

gradually  passing  off  into  the  refinement  of  taste.  The  action  of  any 
given  substance  may  be  increased  by  motion  and  pressure,  as  when  it  is 
rolled  over  the  tongue,  or  held  thereby.  Its  sense  of  discrimination  may 
be  rendered  more  acute  by  education. 

As  with  the  organs  of  the  other  senses,  so  with  this,  an  impression 
Duration  of  made  upon  it  does  not  instantaneously  cease,  but  remains  for 
tastes.  a  certain  period  of  time,  indeed,  in  this  instance  longer  than 

in  those.  Hence  many  substances  acting  in  rapid  succession  give  rise 
to  a  confused  effect,  though  it  is  said  that,  out  of  such  interminglings,  an 
accomplished  epicure  can  fasten  his  attention  on  one,  and  continue  to 
recognize  it  just  as  we  recognize  and  follow  the  sound  of  one  instrument 
in  an  orchestra.  No  explanation  has  as  yet  been  given  of  the  manner 
of  action  of  different  tastes,  though  it  is  asserted  that  some  act  upon  one, 
and  some  upon  another  set  of  the  papillae.  After-tastes  are  also  observed, 
Complement-  which  are  occasionally  of  a  complementary  kind,  as,  for  in- 
ary  tastes.  stance,  the  intensely  bitter  taste  of  tannin  is  followed  by  a 
sweetness.  These  after  effects  modify  the  taste  of  substances  which  may 
be  taken  while  they  last.  They  therefore  form  an  ample  subject  for  the 
profound  contemplation  of  the  epicure,  and  should  occupy  the  serious  at- 
tention of  the  cook.  They  may  be  illustrated  in  a  general  manner  by  the 
injurious  effect  of  sweet  substances  upon  the  flavor  of  delicate  wines. 

It  has  been  mentioned  that  the  passage  of  a  voltaic  current  through 
Electrical  and  ^e  tongue  causes  an  alkaline  or  acid  taste.  Some  experi- 
subjective  menters  deny  the  correctness  of  this  statement,  and  assert 
that  the  impression  is  merely  metallic.  The  effect,  however, 
depends  upon  the  intensity  of  the  current  employed,  or  on  the  nature  of 
the  pieces  of  metal  used.  If  the  current  has  power  enough  to  decom- 
pose the  salts  of  the  saliva,  acid  or  alkaline  tastes  will  be  detected,  ac- 
cording as  the  direction  of  the  current  is  made  to  vary,  and  the  acid  or 
alkaline  body  is  disengaged  on  the  upper  or  under  side  of  the  tongue. 
Subjective  tastes  arise  in  diseases  of  the  nervous  centres,  but  these  are 
often  rendered  obscure  by  the  exudations  and  furred  condition  of  the 
tongue.  Dogs,  into  the  blood-vessels  of  which  milk  has  been  injected, 
have  been  observed  to  lick  their  lips ;  and  from  this  it  has  been  inferred 
that  the  presence  of  substances  artificially  introduced  into  the  circulato- 
ry current  may  be  detected  by  the  organ  of  taste. 


ANIMAL  MOTION.  431 


CHAPTER  XXV. 

OF  ANIMAL  MOTION. 

Ciliary  and  Muscular  Motion. — Description  of  Cilia  and  ike  Manner  of  Action. 

Muscular  Fibre :  its  Forms,  Non-striated  and  Striated. — Muscle  Juice. — Manner  of  Contraction 
of  a  Muscle :  its  supply  of  Blood-vessels  and  Nerves. — Its  Chemical  Change  during  Activity. — 
Its  Rise  of  Temperature. — Effect  of  Electrical  Currents. — Duration  of  Contractility.  • 

Doctrine  that  Muscle  Contraction  is  the  result  of  Muscle  Disintegration. — Manner  in  which  ordi- 
nary Cohesion  is  brought  into  play. — Manner  of  Restoration. — Removal  of  the  Heat  and  Oxi- 
dized Bodies. 

Rigor  Mortis. —  Connection  of  Muscle  for  Locomotion. — Of  Standing. —  Walking. — Running. 

IT  was  formerly  held  that  animals  are  distinguished  from  plants  by 
the  possession  of  the  power  of  locomotion,  a  doctrine  which   . 

r  J   J  TA  i        -u        Animal  motion. 

can  now  no  longer  be  regarded  as  true.  It  was  also  be- 
lieved that  the  muscular  movements  of  animals  are  due  to  the  influence 
of  the  nerves,  and  that  a  muscular  fibre  contracts  only  when  stimulated 
to  do  so  by  a  nerve.  This  makes  the  possession  of  a  nervous  system 
essential  to  the  motions  of  animals.  These  doctrines  also  are  erroneous. 
Animal  motion  is  of  two  different  kinds :  1st.  It  is  accomplished  by 
vibrating  cilia ;  2d.  By  the  contraction  of  cells  arranged  in  the  form  of  a 
fibre. 

OP  CILIARY  MOTION.  . 

The  epithelial  cells  of  the  cylindrical  and  of  the  tesselated  kind  are 
occasionally  arranged  with  delicate  projecting  strige  on  their  Description  of 
free  extremities.  The  length  of  these  varies  from  the  -6-J-Q  cilia  and  their 
to  the  XQOQQ  of  an  inch.  These  stria?  are  termed  cilia,  and 
the  cells  are  said  to  be  ciliated.  Examples  are  presented  by  the  mucous 
Fig.  208  membrane  of  the  respiratory  surface  and  of  the  nasal 

cavities ;  an  illustration  is  given  in  Fig.  208.  The 
cilia  may  be  regarded  as  prolongations  of  the  cell  wall 
itself.  They  exhibit  a  vibrating  motion  back  and 
forth,  which  recalls  the  movements  of  stalks  of  grain 
in  a  field  as  the  wind  is  passing  over  it,  the  ears  bend- 

Ciliated  cells.  ,  ,     .   .  . r    .        °  ,    , 

ing  down  and  rising  again  in  the  breeze,  and  throwing 
the  whole  surface  into  waves.  The  cilia  also  exhibit  a  movement  like 
that  known  as  the  feathering  of  an  oar,  or  sometimes  as  turning  round 
upon  the  point  of  attachment,  as  upon  a  centre,  giving  rise  to  a  sort  of 
conical  motion,  the  free  end  describing  a  circle.  These  motions  seem  to 


432 


CILIARY  MOTION. 


209. 


be  perfectly  involuntary,  for  they  not  only  take  place  long  after  death, 

but  even  in  detached  portions,  the  ciliary  cell  being  uninjured  and  entire. 

The  seats  of  ciliary  action  are  always  moistened  surfaces.     The  condi- 

tion for  the  continuance  of  the  motion  after  death  is  accordingly  that  the 

surface  shall  be  kept  moist,  but  it  is  also  necessary  that  a  certain  tem- 

perature should  be  observed,  which  in  warm-blooded  animals  must  not 

fall  below  42°  F.     Even  after  the  motion  has  completely  ceased,  a  solu- 

tion of  carbonate  of  potash  re-excites  it,  but  this  does  not  take  place  'with 

ammonia,  because  it  injures  the  ciliated  cells. 

Ciliary  motion  is  independent  of  nervous  agency.     The  control  of  tem- 

perature and  of  chemical  reagents  over  it  shows  that  it  is  of  a  physical 

nature. 

In  the  lower  orders  of  life  ciliary  movement  is  relied  on  both  for  the 

Uses  of  ciliary  purposes  of  locomotion  and  prehension. 

motion.        "   pig%  209  illustrates  this  in  the  case  of 

a  vorticella,  the  upper  edge  of  which  shows  such  a 

mechanism.     It  is  often  stated  that  in  the  higher  an- 

imals the  object  is  to  determine  a  movement  of  the 

liquid  which  moistens  the  ciliated  cells  in  the  direc- 

tion of  the  outlet  of  the  tube,  or  other  surface  which 

they  line.     In  this  way  the  action  of  the  cilia  may 

tend  to  the  expulsion  of  material  from  the  air-cells 

of  the  lungs  into  the  bronchial  tubes.     In  reptiles, 

whose  urinary  tubelets  are  furnished  with  this  mech-       ciliated  animalcule. 

anism,  the  secretion  may  be  urged  thereby  in  the  proper  direction. 
The  contractile  tissue  which  enables  such  animals  as  the  hydra  (Fig. 

Embryonic       ^^)  to  execute  movements  of  prehension  and  locomotion 

contractile  tis-  may  perhaps  be  regarded  as  the  rudimentary  state  of  the 
structures  next  to  be  described.     The  annexed  sketch,  from 

Trembley,  illustrates  the 
manner  of  progression  of 
this  animal.  No  trace  of 
a  proper  muscular  fibre, 
and  none  of  a  nervous 
Hydra  walking.  system,  have  hitherto  been 

detected  in  it. 

Of  Muscular  Motion. 

The  muscular  system  consists  of  muscular  fibres,  tendons,  bones,  to- 
gether with  various  accessory  parts,  such  as  ligaments,  sheaths,  bursa3 
mucosiE,  synovial  capsules,  fascia.  Its  action  depends  on  the  primary 
fact  that,  under  appropriate  influences,  muscular  fibre  shortens. 

Each  voluntary  muscle  consists  of  a  collection  of  fasciculi,  which  ex- 


MUSCULAR  FASCICULI  AND  FIBRILS. 


433 


Fig.  211. 


hibit  the  characteristic  appearance 
of  transverse  striation,  as  in  the 

Fig.  212. 


Striated  muscular  fasciculi,  magnified  K5  diameters. 


Sarcolemma  of  fish. 


photograph  of  muscular  structure  of  the  frog  (Fig.  211).  voluntary  mus- 
The  primary  fasciculi  are   collected  into  larger  bundles,  cuiar  fasciculi. 
secondary  muscular  fasciculi,  held  together  by  connective  tissue,  and 
these,  again,  into  still  larger,  the  tertiary. 

The  primitive  fasciculus  is  enveloped  in  a  delicate  sheath,  the  sarco- 
lemma,  as  shown  in.  Fig.  212,  in  which  the  fasciculus,  though  torn  across, 
is  held  together  by  the  sarcolemma.  The  specimen  is  from  the  human 
muscle.  Fig.  213  is  a  good  representation  of  the  same  fact.  It  is  given 
by  Todd  and  Bowman  from  the  skate.  The  sarcolemma  is  a  delicate 
membrane,  which,  though  of  great  tenuity  in  man,  may  be  made  visible 
by  the  action  of  acetic  acid  or  alkalies.  Within  the  sarcolemma  the 
primitive  fasciculus  is  seen  to  be  composed  of  many  parallel  fibrils, 
which  may,  by  maceration  or  chemical  agents,  be  separated  from  one  an- 
other. These  fibrils  present  a  beaded  aspect,  and,  since  their  constituent 
elements  are  arranged  side  by  side  in  parallel  planes,  they  ultimate  mus- 
give  to  the  fasciculus  the  appearance  of  striation  it  presents.  cular  fibril- 

The  longitudinal  striation  of  the  fas- 
ciculus arises  from  the  fibrils  them- 
selves. Here  and  there,  in  the  inte- 
rior of  the  sarcolemma,  nuclei  occur  ir- 
regularly, and  with  them  fat  granules. 
The  fibrils,  with  the  fat  and  a  liquid, 
fill  the  sarcolemma,  without  leaving 
any  central  canal  or  hollow  axis. 

Fig.  214  is  a  photograph  of  ulti- 
mate muscular  fibre  of  the  pig,  from 
one  of  Mr.Lealand's  preparations.  The 
rectangular  form  of  the  constituent 

Ultimate  muscuuTfi^HI^d  200  diameters.    Cells    IS   Well    Seen    at  0,  a,  a.       At  £, 

EE 


-  214- 


434  MUSCLE   JUICE. 

probably  by  reason  of  a  twist,  tension,  or  undue  strain,  a  spiral  appear- 
ance is  presented ;  c,  c  are  the  primitive  fasciculi. 

A  fluid  surrounds  the  fibres  of  striped  muscles,  and  the  fibre  cells  of 

smooth  ones,  which  is  wholly  different  from  the  plasma  of 

Muscle  juice.  ^  ^^     The  experiments  Of  Schultz  show-that  this  fluid 

contains  a  large  amount  of  casein,  a  conclusion  of  considerable  import- 
ance, since,  if  there  were  any  doubt  of  the  occurrence  of  that  substance 
in  the  blood,  this  fact,  at  all  events,  renders  it  certain  that  the  mammary 
gland  is  not  necessary  to  its  formation.  That  the  substance  thus  occur- 
ring is  casein  is  proved  by  the  action  of  rennet. 

Muscle  juice  undoubtedly  arises  within  the  sarcolemma  through  which 
it  exudes.  Each  fibre  therefore  presents  four  objects :  the  syntonin,  the 
nucleus,  the  sarcolemma,  and  the  muscle  juice.  That  the  muscle  juice 
arises  in  part  from  the  functional  activity  of  the  fibre,  and  is  immediate- 
ly derived  from  the  waste  of  its  syntonin,  and  that,  in  its  turn,  the  syn- 
tonin is  closely  allied  to  the  substance  of  the  nucleus,  is  shown  by  their 
exhibiting  almost  the  same  chemical  reactions  with  alkalies,  acids,  etc. 

The  sarcolemma  is  not,  however,  filled  with  syntonin;  it  contains  be- 
sides, as  stated  above,  a  certain  quantity  of  fat,  as  may  be  demonstrated 
by  removing  from  the  sarcolemma  its  syntonin  by  acids,  when  a  granu- 
lar material  will  be  left.  That  this  is  fat  is  proved  by  its  solubility  in 
sulphuric  ether. 

The  sarcolemma  does  not  belong  to  the  protein  class  of  bodies,  but  is 
Sarcolem-  rather  analogous  to  elastic  tissue.  The  color  of  muscle  appears 
ma-  to  be  not  so  much  due  to  the  blood  as  to  a  special  pigment, 

which,  perhaps,  adheres  in  a  free  state  to  the  fibrils.  The  muscle  juice 
contains  relatively  far  more  potash  salts  and  phosphates  than  the  blood, 
as  is  shown  by  the  following  table  from  Liebig. 

For  one  hundred  parts  of  soda  there  occur, 

In  the  hen,     40.8  of  potash  in  the  blood,  and  381  in  the  muscle  juice. 
"     'ox,         5.9  "  "  "  279  "          " 

"      horse,    9.5  "  "  "  285  "          " 

"      fox,       —  "  "  "  214:  "          " 

"      pike,      —  "  "  "  497  "          " 

It  is  commonly  stated  that  muscular  motion  is  accomplished  by  fibres 
Two  forms  of  of  .two  different  kinds:  1st.  The  simple,  non-striated,  un- 
fibre0  n^n  striPe<^  or  organic  fibre ;  2d.  The  striated,  striped,  or  volun- 
stria'ted  and  tary  fibre  just  described.  Though  this  subdivision  may  be 
convenient,  it  can  scarcely  be  regarded  as  accurate,  since  the 
former  variety  passes  by  insensible  degrees  during  development  into  the 
latter,  and  cases,  indeed,  are  not  wanting  in  which  the  same  fasciculus 
presents  in  different  parts  both  conditions  at  once. 

The  non-striated  muscular  fibre.  Fig.  215,  consists  of  translucent  bands 


FORMS  OF   MUSCLE. 

of  a  soft  granular  material,  varying  from  the  -^QQ  to 


Fig.  215.  Fig.  21C. 


an 


435 

m 


Unstriped  fibres. 


Unstriped  fibres  in  acetic  acid. 


Fig.  'ill. 


Muscle 
cells, 


breadth,  and  exhibiting  here  and  there  the  traces  of  Non-stria- 
nuclei,  particularly  after  the  fibre  has  been  acted  on  by  ted  fibre- 
acetic  acid,  as  is  shown  in  Fig.  216.  Each  fibre  may  be  re- 
garded as  an  arrangement  of  nucleated  cells,  the  nucleus  be- 
ing of  a  cylindroid  or  spindle  form.  The  contractile  content 
within  is  syntonin.  Non-striated  fibre  is  not  usually  attach- 
ed to  fixed  points,  as  to  bone,  but  by  being  collected  into  par- 
allel bundles,  different  bundles  interlacing  with  one  another, 
contractile  planes  or  surfaces  are  formed,  such  as  the  cylindri- 
cal coat  of  muscular  structure  of  the  digestive  tube,  or  the 
contractile  layer  of  the  urinary  bladder.  Similar  fibres,  im- 
bedded in  the  skin  and  connective  tissues,  communicate  to 
them  the  quality  of  corrugation  or  contractility.  The  fascic- 
uli are  bathed  externally  with  an  acid  juice,  characterized  by  con- 
taining salts  of  potash,  phosphoric  acid,  creatinc,  nnd  inosite.  The 
general  appearance  of  fibre  cells  of  this  class  is  given  in  Fig.  217 : 
a  is  from  the  small  intestine  of  man ;  £,  from  the  fibrous  invest- 
ment of  the  spleen  of  the  dog.  (Kolliker.) 

Contractile  fibre  cells  present  the  following  reactions :  Acetic 
acid  causes  the  fibre  to  swell,  and  makes  the  nucleus  more  contractile 
visible ;  it  occasions  a  complete  dissolution  when  in  a  fibre-cells- 
concentrated  state.  Dilute  hydrochloric  acts  in  a  similar  manner, 
the  effect  in  this  instance  being  the  same  with  the  fibres  of.  both 
smooth  and  striped  muscle.  The  examinations  thus  far  made  have 
shown  no  difference  in  ultimate  composition  between  these  forms. 
The.  striated  muscular  fibre  consists  therefore  of  fasciculi,  with 
an  elastic  investment  of  sarcolemma,  collected  into  bundles,  striated 
and  invested  with  perimysium.  The  contractile  constituent  .fibre-  • 


436  STRUCTURE   OF   MUSCLE. 

is  syntonin ;  and  though  the  general  rule  is  that  the  primitive  bundles 
shall  run  isolatedly  and  parallel  to  each  other,  in  certain  cases  they  anas- 
tomose, Fig.  60.  In  its  ultimate  construction,  the  form  of  fibre  may  be 
regarded  as  consisting  of  a  series -of  cells,  as  shown  \nFig.  214,  the  di- 
ameter of  which  varies  according  to  the  actual  condition  of  the  muscle, 
whether  it  is  in  the  contracted  or  relaxed  state,  but  which  may  be  taken, 
on  an  average,  at  the  Yoiy  o"o  °f  an  incn-  The  cells  are  placed  end  to  end, 
the  boundary  walls  upon  the  end  presenting  the  appearance  of  a  delicate 
transverse  line.  Each  cell  consists  of  two  portions,  a  central  spot  and 
a  pellucid  border.  The  pellucid  border  is  considered  by  Dr.  Carpenter, 
whose  views  of  muscular  structure  we  are  here  presenting,  to  be  the  cell 
wall,  the  central  space  being  the  cavity  of  the  cell  filled  with  some* highly 
refracting  substance.  Dr.  Carpenter  speaks  of  the  central  spot  as  dark ; 
an  inspection  of  the  photograph,  Fig.  214,  proves  that  it  may  be  light  if 
exactly  in  focus.  When  the  fibril  is  in  a  relaxed  state  the  longest  axis 
of  each  cell  coincides  with  the  length  of  the  fibril,  but  when  contraction 
occurs  this  axis  shortens,  and  a  shortening  of  the  entire  fibril  is  the  re- 
sult. A  number  of  these  fibrils,  placed  side  by  side,  constitute  a  fascicu- 
lus ;  indeed,  there  may  be  many  hundreds  of  them  thus  bound  together. 
When  such  a  fasciculus  is  forcibly  ruptured  it  presents  different  appear- 
ances, according  as  the  ends  or  sides  of  its  constituent  cells  have  cohered 
most  strongly  together.  If  the  lateral  cohesion  is  weakest,  the  fascicu- 
lus tears  into  its  constituent  fibrils,  as  was  shown  in  Fig.  214,  but  if  the 
end  cohesion  is  the  weakest,  it  will  tear  into  discs  or  plates,  as  in  Fig. 
Fig.  218.  218.  The  fasciculus  is  thus  a  bundle  of  fibrils,  its 

diameter  varying  very  greatly,  and  being,  in  man, 
from  the  -^  $  to  the  -g-^  of  an  inch ;  in  females  it 
is,  on  an  average,  smaller.  Each  fibril  is  a  linear 
series  of  coalesced  cells.  The  cells,  as  they  form 
the  fibril,  lose  their  rounded  and  assume  a  rectan- 
gular appearance,  as  shown  at  a,  <z,  Fig.  214.  It 

Muscular  fasciculi  torn         &,         ./.  -,  i     PI     -i  .  i 

in  discs.  therefore  appears  that  each  fibril  must  have  its  own 

investing  sheath,  the  representative  of  the  walls  of  the  little  cells  which 
have  coalesced,  and  this,  though  not  usually  admitted  by  anatomists,  ap- 
pears plainly  in  the  photograph  from  which  that  figure  is  taken.  In 
length,  muscular  fasciculi  vary  fromtthe  sixth  of  an  inch  to  two  feet. 
The  larger  animals  furnish  some  that  are  even  much  longer.  The  nor- 
mal form  is  doubtless  cylindrical,  but  this  is  constantly  departed  from, 
each  accommodating  itself  to  the  pressure  of  the  adjacent  ones.  The 
sarcolemma  serves  as  a  partition  between  its  included  fibrils  and  the  cap- 
illary blood-vessels  and  nerves,  which  imbed  themselves  in  the  rounded 
angular  spaces  between  adjacent  bundles.  The  cross  section  of  a  por- 
tion of  muscle  shows  the  manner  in  which  the  sarcolemma  and  the  fibres 


STRUCTURE    OF   MUSCLE. 


437 


are  arranged.     Fig.  219  is  from  the  human  biceps,  and  Fig.  220  from 


Fig.  219. 


Fig.  220. 


Hansverse  section  of  human  muscle. 

Muscular  fas-  the  pectoral 
cicuii.  muscle  of  the 

teal.  Since  it  is  in  the 
interspaces  between  the 
rounded  fasciculi  that 

the  blood-VeSSels  lie,  the  Transverse  section  of  muscle  of  teal. 

tissue  is  more  vascular  as  its  fasciculi  are  of  less  diameter. 

It  has  already  been  stated,  in  connection  with  Fig.  211,  that  the  stri- 
ated form  of  muscular  fibre  derived  its  name  from  the  circumstance  that, 
when  examined  by  a  sufficiently  high  power,  it  appears  to  be  crossed  by 
delicate  transverse  lines,  the  longitudinal  separations  between  the  fibrils 
being  also  visible.  This  is  seen  in  the  specimen  of  insect  muscle  repre- 
sented in  the  photograph,  Fig.  221,  and  under  a  still  higher  magnifying 


Fig.  221. 


Fig.  222. 


Non-fibrillated  insect  fasciculi,  magnified  50  diameters. 

power  in  that  of  Fig.  222.      The  dis- 
tance between  the  transverse  stria3  va- 
ries with  the  condition  of  the  muscle, 
but  on  an  average  it  is  represented  as    N0n-fibriiiated  insect  fasciculi,  magnified  200 
being  about  the  ¥ ^  of  an  inch.   Many 

more  stria3  are  crowded  together  when  contraction  takes  place,  and  they 
retire  from  each  other  as  soon  as  relaxation  occurs. 

It  is  said  that  the  voluntary  muscles  contain  in  their  muscle  juice 
more  acid  than  is  enough  to  neutralize  all  the  alkali  of  the 


blood.     The  electro-chemical  relations  of  this  interfascicular 


Muscle  juice. 


438 


MANNER   OF   MUSCULAR   CONTRACTION. 


acid  juice  and  the  alkaline  plasma  of  the  blood  are  doubtless  the  cause 
of  the  production  of  those  electric  currents  which  have  been  demonstrated 
in  the  muscles.  It  does  not  follow,  therefore,  that  these  currents  occur 
in  the  natural  state :  they  may  be  the  result  of  the  experimental  arrange- 
ment for  their  own  detection,  since  it  has  long  been  known  that  an  acid 
and  an  alkaline  juice,  separated  from  each  other  by  a  conducting  organic 
body,  will  form  an  effective  voltaic  circle. 

Of  the  contractile  element  of  muscular  fibre,  syntonin,  it  may  be  re- 
marked that  it  can  be  dissolved  by  the  aid  of  dilute  hydrochlo- 
ric acid,  and  that  it  differs  from  fibrin  of  blood  not  only  in  that 
respect,  but  also  both  in  its  ultimate  composition  and  physical  and  chem- 
ical qualities.     In  certain  cases  it  seems  to  degenerate  into  fatty  sub- 
stance.    In  the  growth  of  a  muscle,  the  constituent  fibrils  increase  in 
number  and  in  length,  their  diameter  remaining,  however,  nearly  the 
same  as  in  the  early  periods  of  life.     The  thickening  of  a  muscle  is, 
therefore,  not  so  much  due  to  the  thickening  of  its  constituent  fibrils  as 
to  their  increase  of  number. 

The  contraction  of  a  muscular  fibre  does  not  take  place  throughout  its 
Manner  of  con  wno^e  length  at  once ;  it  generally  begins  at  the  end,  a  change 
traction  of  a  of  aspect  arising  from  the  approach  of  the  opaque  centres  of 
Hie  cells  to  one  another,  and  this  occurring  simultaneously 
across  the  whole  fibre.  This  approach  may,  however,  ensue  in  different 
parts  of  the  length  at  the  same  time,  the  sarcolemma  being  raised  up  in 
bulla3  as  the  contraction  takes- place.  This  effect  is  shown  in  Fig.  223, 


Fig.  223. 


Contracting  muscle  of  Dytiscus. 

in  which  the  thickened  portion  of  the  contracted  middle  space  of  the  mus- 
cle is  surrounded  with  the  sarcolem- 
mic  bullas. 


Fig.  224. 


The  same  is  demon- 
strated in  Fig.  224,  which  repre- 
sents the  border  of  a  muscular  fas- 
ciculus in  a  young  crab,  with  a  spot 
of  contraction,  and  the  sarcolemma 
elevated  along  the  edge.  In  these 
cases  the  contraction  is  brought  on 
by  the  action  of  water,  which,  in 
some  measure,  may  exaggerate  or  disturb  the  phenomena.  Fig.  225 
exhibits,  under  the  same  circumstances,  a  fasciculus  from  the  eel,  a  being 
the  uncontracted,  b  the  contracted  part,  on  the  edge  of  which  the  sarco- 


Sarcolemma  raised  in  bullse. 


ATTACHMENT  OF  MUSCLE  TO  BONE.  439 

Fig.  225.  lemma,  is  again  raised  up.     The  two 

latter  illustrations  are  from  Todd  and 
Bowman. 

Different  portions  of  the  length  of 
the  fibre  assume  this  condition  at  dif- 
ferent moments,  and  hence  the  whole 

Fasciculus  contacting.  structure  is  thrown  into  a  form  which 

recalls  the  motion  of  a  worm.  The  zigzag  appearance  pointed  out  by 
Prevost  and  Dumas  arises  from  the  circumstance  that  when  relaxa- 
tion of  the  fibre  occurs  all  its  parts  are  not  brought  at  once  into  the 
same  state,  but  while  some  are  contracted  others  are  in  the  opposite  con- 
dition. A  muscle,  during  its  contraction,  appears  to  have  nearly  the 
same  solid  dimensions  which  it  had  during  its  relaxation.  This  has  led 
to  the  deceptive  conclusion  that  whatever  it  has  lost  in  length  it  has 
gained  in  thickness.  There  must,  however,  be  a  diminution  correspond- 
ing to  the  recognized  amount  of  waste,  for  it  is  well  known  that  destruc- 
tion of  a  portion  of  its  tissue  is  the  essential  condition  of  the  activity  of 
a  muscle.  The  various  degrees  of  energy  with  which  the  contraction 
takes  place  at  different  times  is  to  be  explained  not  so  much  by  the 
more  or  less  energetic  shortening  of  the  cells  as  by  the  varying  number 
of  fibres  which  are  simultaneously  contracting,  or  by  the  different  frac- 
tional portion  of  each  which  is  going  into  action  at  once.  As  the  mus- 
cular effect  is  more  energetic,  so  will  the  sense  of  fatigue  be  more  speedy, 
for  while  one  fibre  is  acting  another  is  resting,  and  the  same  remark  ap- 
plies to  different  parts  of  even  the  same  fibre.  It  is  to  this  reciproca- 
tion of  motion  that  the  sound  usually  emitted  while  the  muscle  is  in  ac- 
tion, a  low  ringing  sound,  is  to  be  attributed. 

Striated  muscle  is  often  attached  to  bone,  or  other  substance  on  which 
it  has  to  exert  its  mechanical  power,  by  intervening  fibrous  jjuscie  attach 
tissue  constituting  tendon.  These  fibres  are  collected  in  ed  to  bone  by 
groups,  so  as  to  present  primary,  secondary,  and  tertiary  fas- 
ciculi. The  tendinous  fibres  are  brought  in  relation  with  the  sarcolem- 
ma,  and  thus  form  a  sheath  connected  with  adjacent  ones  by  other  de- 
tached fibres.  These  may  be  considered  as  converging  from  all  parts  of 
the  muscle  to  its  extremities,  and  thus  giving  rise  to  its  tendon.  In 
-  226-  some  instances  the  muscular  fibres  attach  them- 

selves to  the  side  of  the  tendon,  which  does  not 
then  undergo  subdivision. 

From  the  peculiar  structure  of  muscular  tis- 
sue, .the  capillary  vessels  which  are  distributed 
to  it  must  run  in  a  direction  for  the  most  part 
parallel  to  its  fibres,  as  in  Fig.  226.      Their 
Distribution  of  muscular  capillaries.  mo<3e  Of  branching,  transverse  and  longitudinal, 


440 


DISTRIBUTION   OF   VESSELS   AND   NERVES. 


Muscular  arteries  and  veins. 

They  never  penetrate 


is  shown  in  Fig.  227,  a  being  .the  artery,  b  the  ^  227. 

.  vein,  c,  capillary  plexus.     Each  ar- 

Distribution  of  '     '       r         J  r 

blood-vessels  to  tenal  branch  has  usually  two  vena3 
muscle.  comites,  and  the  supply  of  these 

capillaries  has  a  general  correspondence  to  the 
number  of  fibrils.  The  lymphatics  are  not  nu- 
merous. Vascular  distribution  to  the  tendons 
is  much  more  sparing.  By  the  muscular  blood- 
vessels a  triple  function  has  to  be  discharged: 
they  furnish  oxidized  blood,  on  which  the  action 
of  the  muscle  depends  ;  they  remove  the  waste 
which  arises  as  the  consequence  of  that  activity ; 
they  also  repair  that  waste  by  presenting  the 
elements  of  nutrition.  The  younger  Liebig  has 
demonstrated  that  a  muscle  can  not  contract  ex- 
cept it  be  furnished  with  oxygen,  and  that,  as 
long  as  the  capacity  for  contraction  continues,  it 
absorbs  oxygen  and  yields  carbonic  acid. 

In  the  same  general  manner  that  the  blood- 
vessels   are    distributed,  so    likewise    are   the 
nerves.     An  example  of  this  is  seen  in  Fig.  228. 
,  the  sarcolemma, 

Distribution  of 

nerves  to  mus-   but  run  ill   close 

contiguity  with 
it,  their  distribution  to  dif- 
ferent parts  of  the  fasciculi 
being  very  unequal,  some 
parts  being  quite  scantily  fur- 
nished, the  nerve  filaments 
coming  in  contact,  as  it  were, 
at  occasional  points.  The 
opinion  is  generally  maintain- 
ed among  physiologists  that 
the  nerves  present  toward 
their  extremities  a  looped  arrangement,  as  shown  in  Fig.  228,  but  by 
some  it  is  asserted  that  the  termination  is  in  an  extremely  delicate  point, 
or  bifid,  or  trifid,  without  exhibiting  any  return.  Of  the  two  forms  of 
muscular  tissue,  the  striated  is,  for  the  most  part,  supplied  from  the  cere- 
bro-spinal  system,  the  non-striated  from  the  sympathetic. 

The  manner  of  development  of  muscular  fasciculus  seems  to  be,  that 
Development  the  sarcolemma  is  first  produced  as  a  thin  and  delicate  tube 
of  muscle.  ^  faQ  coalescence  of  cells  arranged  linearly,  the  walls  of  which, 
where  they  come  in  contact  at  the  ends,  are  obliterated,  giving  origin  to 


Distribution  of  muscular  nerves. 


COMPOSITION   OP  MUSCLE. 


441 


an  elongated  band.  A  granular  material  then  occupies  the  interior  of 
the  tube.  Viewing  the  sarcolemma  as  the  sum  of  the  coalesced  cell  walls, 
the  fibrils  are  to  be  regarded  as  a  development  from  the  granular  cell  con- 
tents. They  form,  by  a  sort  of  endogenous  process,  from  without  to 
within.  The  nuclei,  as  has  already  been  remarked,  are  on  the  inner  sur- 
face of  the  sarcolemma,  and  not  within  the  cells.  The  structure  is  not 
evident  until  after  the  end  of  the  second  month  of  foetal  life,  but  by  the 
fourth  month  it  has  so  much  advanced  that  the  muscle  assumes  a  pale 
red  aspect;  the  tendons,  which  have  already  begun  to  be  distinctly  dif- 
ferentiated, are  gray.  At  birth  the  structure  has  become  so  far  com- 
pleted that  the  fibres  can  be  isolated.  The  condition  which  the  non- 
striated  fibre  presents  is,  therefore,  that  beyond  which  the  striated  fibre 
has  passed,  and  in  this  respect  the  former  may  be  regarded  as  an  embry- 
onic state  of  the  latter.  In  some  insect  muscles  an  instructive  interme- 
diate condition  is  seen ;  fibres  may  be  found  striated  toward  the  middle, 
and  non-striated  at  the  ends,  as  though  imperfectly  developed.  The 
thoracic  muscles  of  insects,  which  offer  a  beautiful  example  of  muscular 
structure,  are  not,  however,  to  be  regarded  as  presenting  primitive  fibrils, 
but  rather  non-fibrillated  primitive  bundles.  This  I  consider  to  be  the 
case  with  the  specimens  from  which  the  photographs,  Figs.  221,  222, 
were  taken.  Though  not  so  apparent,  nuclei  exist  in  the  striated  fibre 
even  of  adult  life,  and  discharge  an  active  function.  At  this  period,  the 
increase  of  thickness  of  the  muscles  is  to  be  attributed  to  an  increase  in 
the  number  of  the  contained  fibrils,  which  individually  have  about  the 
same  dimensions  as  before  birth. 

Composition  of  Ox  Muscle. 


Herzelius. 

Braconnot. 

Marchand. 

Water  

771.70 

770.30 

766.00 

Fibrin,  cells,  vessels,  and  nerves... 
Albumen  and  hsemato-globulin  ... 
Alcohol  extract  and  salts  

177.00 

22.00 
18.00 

181.80 
27.00 
19.40 

180.00 
25.00 
17.00 

10.50 

•     11.50 

11.00 

Phosphates  of  lime  and  albumen.. 

00.80 

1.00 

1000.00 

1010.00 

1000.00. 

Composition  of  Human  Muscle. 


Marchand. 

L'Heritier. 

780.00 

771.00 

Matter  insoluble  in  cold  water  

170.00 

158.00 

Soluble  albumen  and  coloring  matter.... 
Alcohol  extract  with  salts   

23.00 
•      16.00 

34.00 
12.00 

10.00 

25.00 

Phosphate  of  lime  with  albumen  

1.00 

1000.00 

1000.00 

The  result  of  the  chemical  change  which  muscular  fibre  undergoes  dur- 
ing the  periods  of  its  activity  is  eventually  manifested  by  the  Chemical 
appearance  of  carbonic  acid  and  urea,  and  also  salts  of  sulphuric  ^Sct^ity 
acid,  the  two  latter  escaping  from  the  system  through  the  uri-  of  muscle. 


442  FUNCTION   OF   MUSCULAR  FIBRE. 

nary  apparatus  ;  the  former,  in  part,  through  the  lungs.  That  these  prod- 
ucts are  to  be  attributed  to  muscular  waste  is  inferred  from  their  in- 
crease or  diminution  with  increases  or  diminutions  of  muscular  exertion. 
In  the  voluntary  fibres  there  is  commonly  a  necessity  for  repose,  during 
which  repair  of  the  waste  is  taking  place ;  but  in  those  organs  which 
are  in  ceaseless  action,  as  the  heart  and  diaphragm,  the  repair  or  nutri- 
tion goes  forward  at  an  equal  rate  with  the  waste,  and  no  period  of  rest 
is  required.  It  necessarily  happens,  during  the  destruction  of  this  tis- 
eoftem  er  sue  by  tne  arterial  blood,  that  a  rise  of  temperature  must 
atureinmus-  ensue,  and  such  a  rise  has  been  actually  observed  to  the 
L0n*  amount  of  a  degree  or  more,  notwithstanding  the  constant 
tendency  to  the  removal  of  the  heat  by  the  constant  current  of  venous 
blood  flowing  from  the  muscle.  There  is  no  necessity  to  attribute  the 
elevation  of  temperature  to  friction  among  muscular  fibres,  and,  indeed, 
the  amount  that  could  arise  in  that  way  must  be  very  'insignificant,  and 
not  to  be  for  a  moment  compared  with  that  due  to  the  oxidation.  Even 
in  muscles  which  have  been  removed  from  the  body,  and  made  to  con- 
tract by  the  aid  of  magneto-electric  currents,  changes  of  composition  may 
be  detected. 


OF  THE   FUNCTION   OF   MUSCULAR   FIBRE. 


The  mechanical  action  of  muscular  fibre  depends,  as  we  have  seen,  on 
Nature  of  the  shortening  of  the  long  axis  of  the  cells  of  which  the  fibres 
contractility.  are  composed.  To  this  result  the  designation  of  contractility 
is  given,  and  the  property  by  which  the  fibre  is  enabled  to  exhibit  this 
shortening  is  designated,  agreeably  to  the  metaphysical  system  of  the  old 
physiologists,  who  were  content  to  accept  a  word  as  an  explanation  of 
a  fact,  by  the  term  irritability ;  this,  as  being  useless,  may  be  discarded ; 
the  former  we  may  continue  to  employ. 

At  one  time  it  was  supposed  that  the  contraction  of  a  muscular  fibre 
Contractility  depends  so  completely  upon  the  agency  of  the  nervous  system 
enf  on^hf"  that  it;  mignt  ^e  considered  as  the  direct  function  thereof;  but 
nerves.  a  more  critical  examination  of  the  circumstances  of  the  short- 
ening of  the  fibre  cells  shows  that  it  possesses  many  features  in  common 
with  the  same  contraction  of  the  cells  of  plants,  which  have  no  nervous 
system.  The  influence  passing  along  the  nerve  fibrils  is  only  one  out  of 
many  which  can  cause  muscular  contraction.  There  is  abundant  evi- 
dence in  support  of  the  position  that  contractility  is  the  result  of  the 
structure  of  the  muscular  fibre,  and  that  it  belongs  to  it,  and  is  not  a  spe- 
cial function  of  nerves. 

When  muscular  fibres  are  touched  by  a  pointed  instrument,  they  ex- 
hibit contraction  even  after  they  have  been  detached  from  the  body,  pro- 
vided that  too  long  a  period  of  time  has  not  elapsed.  If  it  be  of  the  stria- 


CONTEACTION   OF  MUSCULAR  FIBRE.  443 

ted  variety,  the  bundle  that  has  been  disturbed  alone  contracts,  —  ~ 

-,1P  '    Difference  in 

and  presently  alter  relaxes ;  but  there  is  no  lateral  spread  or  the  contrac- 
diffusion  of  the  effect  to  adjacent  bundles,  except  in  the  case  teTlndton-" 
of  the  heart,  in  which  it  would  appear  that  the  contraction  of  striated  mus- 
one  part  is  diffused  laterally,  and  a  single  disturbance  is  fol-  cles' 
lowed  by  many  alternating  contractions  and  relaxations,  simulating,  as  it 
were,  the  normal  function  of  the  whole  organ.  But  where  the  non-stria- 
ted form  is  in  like  manner  examined,  the  contraction  takes  place  more 
slowly,  spreads  laterally  to  a  wider  extent,  and  is  followed  by  a  relaxa- 
tion. The  effect  of  an  intermitting  magneto-electric  current  is  different 
in  the  two  forms  of  tissue,  the  striated  contracting  and  keeping  Effect  of 
contracted  as  long  as  the  action  is  kept  up,  but  the  effect  ceasing  electrical 
when  the  current  stops.  In  the  non-striated  the  action  is  tardy,  ° 
and  relaxations  may  ensue  even  while  the  current  is  passing,  and  con- 
tractions continue  to  occur  after  it  has  stopped.  The  effect  becomes  of 
more  interest  when  a  weak,  continuous  electrical  current  is  passed  through 
the  centrifugal  nerves  supplying  any  muscle,  for  then  the  whole  muscle 
contracts,  and  remains  in  that  state  as  long  as  the  current  flows.  If  the 
current  be  passed  through  the  ganglionic  centre  of  those  nerves  contrac- 
tion again  ensues,  and  is  maintained  for  a  time  even  after  the  current  has 
ceased.  If  the  current  be  sent  through  the  centripetal  fibre,  alternate 
contractions  and  relaxations  of  the  muscle  are  the  result.  The  interpret- 
ation of  these  different  cases  has  already  been  given  (p.  276). 

The  capability  of  contracting  continues  in  muscle  fibre  for  a  certain 
time  after  death,  a  period  which  is  shorter  as  the  rate  of  res-  Experiments 
piration  is  higher,  and  hence  these  effects  were  first  observed  of  Gaivani. 
by  Gaivani  and  others  in  the  case  of  the  frog  and  cold-blooded  animals. 
Even  after  it  has  disappeared,  it  may  be  re-established  by  Ex  eriments 
continuing  the  supply  of  arterial  blood,  as  Dr.  Brown- Sequard  of  Brown-Se- 
has  shown :  a  fact  which  illustrates  in  a  striking  manner  the  quai  ' 
independence  of  the  muscular  contraction  of  the  nervous  system.  Of 
course,  as  would  have  been  expected,  whatever  interferes  with  due  arte- 
rialization*  interferes  with  muscular  power.  This  is  the  reason  of  the 
inability  for  exertion  which  is  experienced  in  the  thin  air  of  mountain 
tops,  the  relaxation  of  the  muscular  system  in  asphyxia,  the  same  con- 
dition in  the  respiration  of  the  vapors  of  ether  or  of  chloroform  ;  it  is  also 
to  a  great  extent  the  cause  of  the  wayward  and  staggering  gait  of  the 
drunkard.  The  converse  of  this  likewise  holds  good :  the  higher  the  rate 
of  respiration,  the  more  energetic  the  muscular  power ;  and  therefore,  in 
birds,  which  respire  most  perfectly,  muscular  contractility  is  exhibited 
with  the  greatest  energy. 

The  contractility  of  the  muscular  tissues,  as  being  independent  of  the 
activity  of  the  nervous  system,  is  well  illustrated  by  the  remarkable  ob- 


444  DOCTRINE   OF   MUSCULAR   CONTRACTION. 

Experiments  servations  of  Dr.  Dowler,  of  New  Orleans,  on  the  automatic 
of  Dr.  Dowler.  movements  that  sometimes  take  place  after  death  by  yellow 
fever.  After  respiration  had  ceased,  each  hand  in  succession  was  car- 
ried to  the  throat,  and  then  to  the  crown  of  the  head,  and  so  back  again 
to  the  breast.  In  another  instance,  on  being  stimulated  by  a  blow,  the 
arm  was  extended  upward,  and  the  hand  could  even  be  made  to  slap  the 
mouth ;  or  when  the  leg  hung  down,  if  the  flexors  of  the  hamstring  were 
struck,  the  heel  was  drawn  upward.  These  manifestations  continued 
for  between  three  and  four  hours,  and  even  occurred  in  amputated  limbs. 

Contractility  lasts  for  a  different  period,  not  only  in  different  animals, 
Duration  of  but  even  in  different  parts  of  the  same  animal.  Thus,  in  man, 
contractility,  ft  declines  in  the  following  order:  in  the  left  ventricle  first, 
then  in  the  intestines  and  stomach,  the  urinary  bladder,  right  ventricle, 
oesophagus,  iris,  in  the  voluntary  muscles  of  the  trunk,  lower  and  upper 
extremities,  and,  finally,  in  the  left  and  right  auricle  of  the  heart. 

Assuming  that  the  diameter  of  each  muscular  fibre  is,  on  an  average, 
Distance  at  the  10Q00  of  an  inch,  and  that  each  fasciculus  is  the  -^  of 
which  a  muscle  an  inch,  it  may  be  inferred  that  each  fasciculus  contains  about 
enced  by^a  U  650  fibres.  Now,  since  the  nerves  do  not  penetrate  the  sar- 
nerve.  colemma,  the  influence  which  they  exhibit  must  be  efficacious 

at  a  distance;  and  if  we  take  the  maximum  measurements  which  have 
been  made  of  muscular  fasciculus,  we  may  safely  conclude  that  that  in- 
fluence extends  at  least  through  a  distance  of  -^J-g-  part  of  an  inch. 

It  is  not  necessary  for  us,  in  this  place,  to  enter  on  a  discussion  of  the 
T  functions  of  nerve  fibres,  whether  they  exert  a  magnetic 

that  muscular  agency,  or  act  by  rise  of  temperature,  or,  from  an  abrupt  po- 
suHsTronimus-  ^ar  termmati°n  deprived  of  its  white  substance  of  Schwann 
cuiar  disinte-  permit  the  escape  of  their  current  into  the  muscle  fibril,  and 
thence  into  the  corresponding  denuded  pole  of  a  centripetal 
nerve  beyond,  the  current  being  determined  through  the  muscle  by  rea- 
son of  the  better  conducting  power  of  that  structure.  The  immediate 
cause  of  muscular  contraction  is  to  be  sought  for  in  the  muscles  them- 
selves, and  this,  I  think,  is  much  more  obvious  than  is  generally  sup- 
posed. So  far  from  there  being  any  thing  mysterious  or  incomprehen- 
sible about  it,  as  some  writers  insist,  we  probably  shall  not  be  very  far 
from  the  truth  if  we  assert  that  muscular  contraction  is  the  necessary 
physical  result  of  muscular  disintegration,  and  without  here  consider- 
ing the  various  ways  by  which  that  muscular  disintegration  may  be 
brought  about,  such  is  the  doctrine  that  I  now  present. 

Reviewing  the  various  conditions  under  which  contraction  occurs,  I  re- 

•  Change  in  mus-  Sar(^  destructive  metamorphosis  as  the  primary  and  leading 

cie  after  con-     one.     Every  thing  seems  to  indicate  that  the  contraction  of 

a  fibril  can  not  take  place  without  the  loss  of  a  part  of  its 


CHANGE  IN  MUSCLE   BY   CONTRACTION. 


445 


substance,  and  this  ensues  even  in  the  artificial  motions  that  are  estab- 
lished by  electric  currents  in  amputated  muscles,  as  is  satisfactorily  shown 
by  the  experiments  of  Helmholtz.  Of  these  the  following  synopsis  is 
given  by  Dr.  Day  : 

"  Powerful  muscular  contractions  were  induced  by  passing  an  electric 
current  through  the  amputated  leg  of  a  frog  as  long  as  convulsions  con- 
tinued to  be  manifested.  The  flesh  of  both  legs  was  then  analyzed. 
The  albumen  was  apparently  scarcely  affected,  the  mean  of  six  experi- 
ments giving  210  per  10,000  of  albumen  in  the  electrized,  and  213  in 
the  non-electrized  flesh.  With  regard  to  the  extractive  matters,  it  ap- 
peared that  in  all  the  experiments,  without  a  single  exception,  the  water 
extract  in  the  electrized  flesh  was  diminished,  while  on  the  other  the 
spirit  and  alcohol  extracts  were  increased.  The  results  are  expressed  in 
the  following  tables : 

Change  in  Muscle  after  Ekctric  Contraction. 
Alcohol  extract  from  100  parts  recent  frog's  flesh. 


Exp. 

a.  In  electrized  portion. 

b.  In  non-electrized  portion. 

a:  b 

1 
2 
3 
4 
5 

6 

7 
8 
9 
Mean 

0.752 
0.569 
0.664 
0.652 
0.575 

0.606 
0.427 
0.481 
0.493 
0.433 

.24:1 
.33:1 
.38:1 
.32:1 
.33:1 

Extracted  with  alcohol  of  95  per  cent. 

1.020 

0.748 

1.36  :  1 

Water  extract. 

Spirit  extract. 

a. 

b. 

a:  b 

a. 

6. 

a:b 

1.21 
0.93 
0.72 
0.95 

1.63 
1.23 
0.90 
1.25 

0.79  :  1 
0.76  :  1 
0.80  :  1 
0.78  :  1 

1.69 
1.65 
1.76 
1.70 

1.50 
1.35 
1.53 
1.46 

1.13:1 
1.22:1 
1.15:1 
1.16:1 

"  The  amount  of  fat  was  unaffected.  No  urea  could  be  found  in  the 
alcohol  extract. 

"There  is  great  difficulty  in  performing  experiments  of  this  nature  on 
warm-blooded  animals,  in  consequence  of  the  rapidity  with  which  iso- 
lated portions  of  the  muscle  lose  their  contractility. 

"  The  best  results  were  obtained  with  decapitated  pigeons : 


a.  In  electrized  muscle. 

b.  In  non-electrized  muscle. 

a:b 

Albumen  
Water  extract 
Spirit  extract. 

2.04 
0.64 
1.68 

2.13 
0.73 
1.58 

.88  :  1 
1.06:1 

"  The  above  facts  sufficiently  show  that  muscular  action  is  always  ac- 
companied by  a  chemical  change  in  the  composition  of  the  acting  mus- 
cle." It  appears  that  after  electrization  the  alcohol  extract  increases  be- 
tween 24  and  38  per  cent. ;  the  water  extract  diminishes  between  24  and 
20  per  cent. ;  the  spirit  extract  increases  between  13  and  22  per  cent. 

I  therefore  regard  disintegration  of  the  muscular  structure  as  the  prim- 
itive act,  so  far  as  the  fibril  itself  is  concerned,  and  contraction  as  the 


446  MANNER   OF   CONTRACTION. 

Balanced  state  necessary  consequence,  that  disintegration  being  brought 
of  a  muscle  about  by  the  oxidizing  agency  of  arterial  blood.  It  must, 

through  waste  J  i  i 

and  repair.  however,  be  borne  in  mind  that  this  waste  is  masked  by  its 
incessant  repair,  and  that  its  condition  at  any  moment  of  its  action  repre- 
sents the  actual  balancing  at  that  instant  of  the  waste  and  repair  re- 
spectively ;  and  since  the  repair  does  not  proceed  with  the  same  rapidity 
as  the  destruction,  it  needs  must  follow  that,  sooner  or  later,  a  point  will 
be  arrived  at  when  there  is  an  absolute  necessity  for  repose  to  give  to 
the  renovating  processes  the  opportunity  or  time  for  effecting*  a  complete 
restoration. 

Accepting,  therefore,  the  fact  that  a  fibre  can  not  contract  without  loss 
Manner  in  °^  *ts  substance,  an^  regarding  that  loss  as  the  cause  and  the 
which  contrac-  contraction  as  the  effect,  it  is  plain  that  whatever  influence 
ccurs'  can  accomplish  an  oxidation  will  produce  a  shortening  of  the 
fibre.  Perhaps  it  may  be  that  the  nerve  tubule  does  it  by  occasioning  a 
rise* of  temperature;  perhaps  it  may  be,  if  nerves  do  not  end  in  loops, 
but  in  denuded  points,  by  the  current  escaping  into  the  muscle  from 
those  points,  and  occasioning  such  an  allotropic  change  in  the  contents 
of  the  muscle  cells  as  enables  the  blood  to  destroy  them,  in  the  manner 
set  forth  in  Chapter  X.  With  such  theories  we  need  not  now  embar- 
rass ourselves,  but  confine  our  attention  to  the  result  with  which  we  are 
concerned,  that  is  to  say,  the  destruction  of  the  material  contained  in  the 
muscle  cells,  which  destruction  is  practically  brought  about  by  the  ac- 
cess of  arterial  blood.  When  this  takes  place,  the  cell  affected  under- 
goes an  actual  diminution  of  size,  through  loss  of  part  of  its  contained 
material,  its  longer  axis  shortening  from  no  other  cause  than  the  cohe- 
sion of  its  included  granules  thus  suddenly  brought  into  play.  The  cell 
which  we  have  under  consideration,  like  an  entire  muscular  fasciculus, 
Restoration  of  Possesses  no  power  of  active  dilatation,  and  so  remains  with- 
the  contracted  out  change  until  it  is  stretched  by  similar  contractions  tak- 
ing place  in  the  components  of  other  and  perhaps  distant 
antagonist  muscles.  Coincident,  however,  with  this  destruction  of  its 
interior  substance,  and  loss  of  its  prolate  form,  is  the  act  of  repair,  the 
nucleus  of  the  cell  reproducing  other  granules  from  materials  furnished 
by  the  blood ;  for  the  arterial  capillaries  not  only  bring  the  means  of 
oxidation,  but  they  bring  the  plastic  elements  of  nutrition,  and  so  per- 
mit the  cell  to  recover  its  dimensions,  and  to  be  stretched  to  its  orig- 
inal shape  by  the  contraction  of  antagonist  fibres.  The  destruction  was 
almost  instantaneous ;  the  repair  is  an  affair  of  a  little  longer  time,  and 
thus,  while  one  part  is  resting,  other  portions  of  the  muscular  mass  take 
up  the  action  in  succession,  one  after  another  contracting.  Such  is  the 
first  series  of  changes ;  let  us  now  examine  the  second. 

For,  as  the  result  of  that  first  stage,  there  has  been  a  liberation  of  prod- 


PRODUCTS  OF  MUSCULAR  WASTE.  447 

nets  of  oxidation,  which  are  eventually  to  find  their  way  into  the  urinary 
secretion,  or  to  escape  by  the  respiratory  surfaces.  It  is  immaterial  what 
the  first  aspect  of  these  substances  may  be,  creatine,  urea,  extractive,  etc. ; 
this  much  is  absolutely  certain,  that  they  are  on  the  downward  career, 
and  will  end  as  urea,  sulphuric,  carbonic  acids,  etc.  The  experiments 
both  of  Reymond  and  Liebig  prove  that  the  muscles,  when  at  Products  of 
rest,  contain  no  acid  juice,  and  during  their  activity  it  is  known  muscular 
that  the  degree  of  acidity  is  proportional  to  the  energy  with  * 
which  they  have  been  contracting.  It  can  not  for  a  moment  be  sup- 
posed that  this  acidity  is  the  cause  of  the  contraction  ;  on  the  contrary, 
it  is  its  result. 

Among  the  products  arising  during  muscular  action  may  be  more  par- 
ticularly mentioned  inosite,  or  muscle  sugar,  which  is  isomeric  inosite  and 
with  glucose,  and  creatine,  which,  though  it  contains  so  large  creatine- 
a  proportion  of  nitrogen,  must  be  regarded  as  a  product  of  the  waste  go- 
ing on.  By  the  loss  of  two  atoms  of  the  element  of  water,  it  gives  origin 
to  creatinine,  which  is  accordingly  found  in  the  muscle  juice,  the  blood, 
and  the  urine.  Indeed,  these  two  substances  seem  to  be  inversely  pro- 
portional to  each  other. 

The  partial  oxidation  which  has  given  rise  to  these  various  products 
can  not  occur  without  an  elevation  of  temperature.  A  second  stage  of 
the  process  of  muscular  action  consists  in  the  removal  of  the  heat  and 
of  the  partially  oxidized  bodies. 

We  have  only  to  look  at  the  minute  anatomy  of  the  parts  under  con- 
sideration to  recognize  the  manner  in  which  this  double  re-  Removal  of  the 
moval  is  accomplished.  The  arterial  capillaries,  when  they  ^zed^dies  by 
break  up  for  their  final  distribution,  run  parallel  with  the  the  blood. 
muscular  fibres,  as  also  do  the  attendant  veins.  From  one  to  the  other, 
at  short  intervals,  as  seen  in  Fig.  227,  intercommunicating  vessels  trans- 
versely pass,  the  whole  being  arranged  on  such  a  system  as  to  afford 
the  readiest  means  of  removal  of  the  blood  as  fast  as  it  becomes  venous 
— a  facility  of  removal  of  the  last  importance  for  carrying  off  the  wasted 
products  of  oxidation ;  and  in  this  manner,  those  products,  whatever  they 
may  in  the  first  instance  be,  find  a  ready  means  of  escape,  and  so  the 
muscular  fibre  by  degrees  is  relieved  from  these  results  of  functional  ac- 
tivity. 

As  for  the  heat  which  has  arisen  in  a  secondary  way  from  the  meta- 
morphosis which  has  been  going  on  in  the  fibre,  that  is  in  like  manner 
extracted.  It  is  difficult  to  conceive  of  a  more  effective  method  by  which 
the  heat  could  be  taken  away  from  the  wasted  fibre,  or  indeed  we  might 
say  from  the  interior  of  the  whole  mass  of  the  muscle.  The  current  of 
vendus  blood  bears  away  with  it  not  only  the  products  that  have  arisen 
in  the  oxidation,  but  likewise  the  heat. 


448  .          RHYTHMIC   CONTRACTION. 

It  is  probable  that  one  cause  of  cessation  of  muscular  contraction  in 
Effect  of  accu-  any  one  point  of  a  fibre  is  the  momentary  accumulation  of 
mulation  or  wasted  material,  as  might  be  illustrated  in  a  coarse  manner 
rial.  by  the  difficulty  of  causing  a  fire  to  continue  burning  when 

the  ashes  are  permitted  to  accumulate,  and  the  necessity  of  their  removal 
before  the  combustion  can  go  on.  Two  separate  events  have  to  occur 
before  a  fibril  that  has  been  in  contraction  is  ready  to  contract  again : 
these  are  the  removal  of  the  oxidized  products,  and  the  renovation  of  the 
interior  of  the  cells.  The  two  probably  go  on  coincidently,  the  veins 
taking  one  part  of  the  duty,  and  the  arterial  capillaries  the  other. 

In  non-striated  muscular  fibre,  in  which  the  supply  of  blood-vessels  is 
Peculiarity  in  much  less  copious,  there  is  a  possibility  for  a  lateral  propa- 
S^onltrilted  gation  of  effect,  because  of  the  possibility  of  the  lateral  prop- 
fibre,  agation  of  the  heat,  either  supplied  directly  from  the  nerve 
tubule  or  arising  from  the  oxidation  going  on.  The  sluggishness  of  its 
first  contraction,  the  longer  continuance,  the  propagation  from  fibre  to 
fibre  laterally  until  the  effect  wears  out  or  is  re-enforced  by  some  new 
stimulus,  might  almost  seem  to  be  the  necessary  result  of  the  imperfect 
supply  of  arterial  blood,  the  sluggish  removal  of  the  products  of  waste, 
and  the  more  perfect  opportunity  for  the  diffusion  of  heat.  This  doc- 
trine therefore  meets  with  a  very  happy  illustration  in  the  phenomenon 
displayed  by  the  contraction  of  the  two  kinds  of  fibre. 

It  may  still  farther  illustrate  these  views  to  examine  that  other  variety 
Rhythmic  con-  of  contraction,  rhythmic  in  its  nature,  which  is  exhibited,  for 
tractions.  example,  by  the  heart,  of  which  it  may  be  said  that  the  fibres 
show  a  simultaneous  contraction  alternating  with  periods  of  repose,  con- 
traction and  relaxation  succeeding  each  other  at  definite  intervals.  If, 
as  we  have  just  said,  the  cessation  of  contractility  arises  from  the  mo- 
mentary accumulation  of  products  of  waste,  and  the  capacity  for  its  re- 
newal is  due  to  restoration  of  the  original  state  by  nutrition,  rhythmic  ac- 
tion may  follow  as  the  consequence  of  an  arrangement  of  muscular  fibrils 
with  an  adjusted  supply  of  arterial  and  venous  capillaries.  An  original 
excitation  producing  a  contraction  can  not  act  in  a  permanent  way,  for 
the  result  of  that  contraction  is  an  accumulation  of  wasted  material  which 
must  be  removed.  It  may  require  but  a  moment  for  the  removal  to  take 
place  to  a  sufficient  extent  to  enable  the  original  disturbance  to  act  once 
more,  and  be  checked  in  its  action  again.  Whatever  value  there  may 
be  in  such  explanations  as  these,  they  undoubtedly  gather  a  deep  inter- 
est from  thus  enabling  us  to  comprehend  that  it  is  possible  to  resolve 
such  mysterious  phenomena  as  rhythmic  periodicities  into  the  results  of 
ordinary  mechanical  laws. 

But  the  question  returns  upon  us.  Admitting  the  descriptions  that 
have  now  been  given  to  be  a  true  representation  of  the  facts,  and  also  of 


CONTRACTION   OF  MUSCLE.  449 

their  natural  sequence,  what  is  the  actual  physical  cause  of 

the  shortening  of  the  muscular  fibril?     All  that  we  have  extensive  mus- 

thus  far  said  can  Ibe  received  at  the  best  as  only  a  statement  cuiar  contrac- 

•f  tion  by  slight 

of  a  succession  or  order  of  facts.  To  say  that  that  shorten-  muscular 
ing  is  the  direct  consequence  of  loss  of  material  involves  us  waste* 
at  once  in  the  inquiry  whether  it  be  possible,  through  the  destruction  of 
so  small  an  amount  of  material  as  we  know  to  occur,  that  any  thing  like 
the  required  extent  of  motion  could  be  produced.  Could  a  muscle  be 
made  to  shorten  several  inches,  and,  upon  these  principles,  lose  only  an 
insignificant  amount  of  weight,  the  shortening  being  nevertheless  the 
consequence  of  that  loss  of  weight  or  destruction  of  substance  ?  To  an- 
swer this  inquiry,  we  have,  in  the  first  place,  to  recall  the  fact  that  a 
whole  muscle  is  never  in  contraction  at  once,  but  only  an  insignificant 
portion  thereof,  one  bundle  of  fibrils  after  another  taking  up  the  action  in 
succession,  and  each  particular  fibril  undergoing  change,  not  throughout 
its  whole  length,  but  only  in  isolated  portions  here  and  there.  We  have, 
moreover,  to  recall  the  insignificant  weight  of  these  fibrils,  for  a  simple 
computation  will  show  that  thirty  thousand  of  them  a  foot  long  weigh 
only  a  single  grain.  To  these  recollections  we  should  add  the  intense 
energy  of  the  molecular  force  of  attraction,  as  displayed  at  such  distances 
as  those  which  we  have  here  under  consideration — distances  which  we 
may  regard  as  being  virtually  inappreciable,  and  these  recollections  place 
the  problem  in  its  true  light,  and  set  it  in  its  proper  attitude  before  us. 

For  it  is  capable  of  demonstration  that  muscular  contraction  ensues  as 
the  direct  consequence  of  destruction  of  muscular  substance,  and  that  a 
great  linear  extent  of  movement  may  be  accomplished  by  the  removal  of 
an  insignificant  amount  of  substance.  If  100,000  fibrils  lost  one  third 
of  their  entire  substance — -a  thing  which,  of  course,  could  scarcely  take 
place — the  diminution  of  weight  would  only  amount  to  a  single  grain. 
Our  conception  of  this  action  may  perhaps  be  rendered  clearer  by  an  il- 
lustration. If  we  had  an  iron  thread  of  excessive  tenuity,  illustration  of 
composed,  for  instance,  of  a  single  row  of  iron  atoms  set  end  ofa^usTte^ 
to  end,  and  could,  by  suitable  processes,  effect  the  removal,  fibre. 
here  and  there,  of  atoms  in  the  line,  an  instantaneous  contraction  would 
be  the  result,  the  thread  shortening  in  proportion  to  the  number  of  atoms 
removed,  but  shortening  with  an  energy  commensurate  with  the  cohesive 
force  of  the  iron  itself,  and  yet  ready  to  return  to  its  original  length  the 
moment  that  fresh  iron  atoms  present  themselves  to  be  introduced  in  the 
place  of  the  abstracted  ones ;  and  so  with  muscular  fibre,  the  molecular 
force  of  cohesion  developed  here  and  there  by  the  removal  of  tissue  is  to 
be  measured  only  by  the  cohesion  of  the  fibre,  though  the  loss  of  mate- 
rial which  may  have  been  the  cause  of  that  force  coming  into  play  may 
be  very  small  indeed;  nor  does  the  quickness  of  relaxation  present  any 

FF 


450  VOLUME  OF  CONTEACTING  MUSCLE. 

difficulty  when  we  consider  the  rapidity  with  which  interstitial  nutrition 
takes  place,  and  the  small  quantity  of  matter  to  be  supplied. 

We  have  now  analyzed  the  phenomenon  of  muscular  contraction,  and 
set  forth  the  conditions  on  which  it  depends.  These  we  may 
ment  of  this  here  reproduce  together  for  the  more  distinct  continuation  of 
doctrine.  ^Q  argument.  The  primary  act  is  the  destruction  of  the 
muscular  material  by  the  agency  of  arterial  blood;  an  incipient  oxidation 
setting  in,  the  wasting  particles  can  no  longer  retain  the  places  they  have 
occupied.  They  have  lost  their  hold  on  the  particles  with  which  they 
were  associated.  At  that  instant  molecular  attraction  comes  into  play, 
and  shortening  of  the  fibre  is  the  result.  The  wasted  material  is  already 
being  absorbed  by  the  venous  capillaries,  and  already  repair  is  taking 
place  by  the  introduction  of  new  fibrinous  material  from  the  arterial 
blood;  but  the  renewal  or  repair  proceeds  much  more  slowly  than  the 
removal  of  the  waste ;  the  latter  effect,  as  might  be  inferred  from  what 
has  been  said  under  the  head  of  absorption,  occurs  almost  instantly,  the 
former  gradually;  and  thus  muscular  contraction  presents  itself  as  a 
composite  result,  depending,  under  normal  circumstances,  partly  on  oxi- 
dation, partly  on  removal  of  waste,  partly  on  repair  by  nutrition,  yet  so 
that  if  any  one  of  these  conditions  be  interfered  with  it  can  not  take  place 
at  aU. 

I  can  not  at  this  point  avoid  offering  a  criticism  on  the  experiments 
Volume  of  a  ^7  which  it  has  been  attempted  to  prove  that  a  muscle,  when 

muscle  after  it  contracts,  loses  none  of  its  bulk ;  the  loss  that  does  in  real- 
contraction.  ..  .,  .  .  ,  , 

ity  occur  is,  it  is  true,  very  minute,  perhaps  so  minute  that,  in 

the  coarse  apparatus  which  has  been  resorted  to  in  these  experiments,  it 
Fig.  229.  .•  would  be  altogether  inappreciable.  Such  a  contrivance  is 
represented  in  Fig.  229,  in  which  <z,  a  is  a  wide  tube  for 
containing  the  muscle,  g;  it  is  also  to  be  filled  with  water, 
and  from  its  side  a  narrow  tube,  d,  projects,  the  water 
reaching  to  some  such  point  as  e.  The  tube,  a,  a,  being 
closed  at  both  its  extremities  water-tight  by  means  of  corks, 
#,  <?,  whenever  the  muscle  is  made  to  contract  by  an  elec- 
tric current,  applied  by  means  of  the  spring  wires,  /",  f,  or 
otherwise,  if  enlargement  occurred  the  water  would  rise  at 
0,  and  if  diminution  it  would  descend ;  but  as,  upon  trial, 
it  is  found  that  no  movement  whatever  takes  place,  it  has 
been  inferred  that  the  volume  of  the  muscle  remains  un- 
changed. But  no  compensation  whatever  for  temperature 
is  provided  !  Yet  it  is  positively  known  that  when  a  mus- 
cle contracts  it  becomes  warm,  and,  doubtless,  these  in- 

Volume  of  contract-     J  -/.-IT  -,  i  i   -i  ^    -i    ,       ,  i 

*  ing  muscle.  struments,  if  delicate  enough,  would  have  led  to  the  pre- 
posterous conclusion  that  a  muscle  after  contraction  is  larger  than  it  was 


CONTRACTION  BY  WATER.  451 

before.  But,  even  setting  disturbances  of  temperature  aside,  such  ex- 
periments are  of  no  kind  of  value,  since  they  contain  no  provision  for  the 
removal  of  the  wasted  material  of  the  muscle,  which  still  continues  a  part 
thereof,  though  it  has  become,  to  all  intents  and  purposes,  extraneous, 
and  would,  if  in  the  living  system,  have  been  instantly  removed  by  the 
veins. 

And  now,  by  the  aid  of  these  doctrines,  we  may  comprehend  the  full 
significance  of  those  conditions,  which  have  been  long  known 
to  physiologists,  which  have  cast  such  a  mystery  over  muscu-  of  partial  hy- 
lar  contraction,  and  led  to  such  a  diversity  of  views  as  re-  P°theses-  + 
spects  its  true  explanation.  We  see  that  they  were  right  who  asserted 
that  muscular  contraction  is  a  function  of  nutrition,  though  they  were 
wrong  in  saying  that  it  is  therefore  of  a  vital,  and  consequently  of  an 
inexplicable  nature.  They,  too,  were  right  who  asserted  that  muscular 
contraction  depends  on  respiration,  and  that  the  higher  the  rate  of  that 
function  the  more  energetic  the  muscular  power  will  be.  They,  too,  were 
right  who  asserted  that  muscular  contraction  is  manifested  by  a  waste 
of  tissue,  and  that  that  waste  may  be  measured,  if  certain  corrections  are 
applied,  by  the  quantity  of  urea  and  sulphuric  acid  in  the  urine.  They, 
too,  were  right  who  asserted  that  there  is  a  connection  between  the  co- 
agulability of  the  blood  and  the  energy  of  muscular  contraction  in  the 
various  tribes  of  life,  for  the  speed  of  repair  depends  on  the  percentage 
of  fibrin  in  the  blood,  and  so,  too,  does  the  speed  of  coagulation.  They, 
too,  were  right  who  asserted  the  connection  between  muscular  contrac- 
tion and  the  speed  or  slowness  of  the  circulation  of  the  blood.  All  these, 
and  many  other  partial  hypotheses,  are  the  necessary  consequences  of  the 
more  general  doctrine,  that  muscular  contraction  is  the  result  of  loss  of 
muscular  substance. 

There  remains  a  phenomenon  to  which  our  attention  has  to  be  direct- 
ed in  the  conclusion  of  this  subject.  It  is  the  contractions  _  t 

.  .  .  -,-,  nil-  -i.  r       •  Contraction 

which  may  be  observed  under  the  microscope  when  a  lascicu-  produced  by 
lus  is  submitted  to  water.  These  contractions  commence  in  water' 
isolated  places,  from  which  they  spread  in  all  directions,  and  so  move 
about  from  end  to  end,  often  interfering  with  one  another,  the  fasciculus 
thickening  where  the  contraction  is  greatest,  and  eventually  the  whole 
length  becoming  involved.  The  ultimate  degree  of  contraction  that  can 
be  reached  reduces  the  fasciculus  to  one  third  of  its  original  length.  With 
this  contraction,  through  the  agency  of  water  or  other  such  liquids,  we 
may  connect  those  contractions  which  ensue  under  the  pressure  or  dis- 
turbance  of  some  hard  body,  as  by  the  touch  of  a  pin. 

From  these  cases  it  might  be  supposed  that  muscular  contractility  can 
take  place  independently  of  chemical  destruction,  but  a  more  critical  ex- 
amination of  them  will  satisfy  us  that  they  ensue  as  the  natural  conse- 


452  RIGOR    MORTIS. 

quences  of  the  preceding  views.  They  are  not  to  be  regarded  as  pure  or 
uncomplicated  manifestations  of  the  qualities  of  muscular  fibre  itself,  but 
as  the  consequences  of  the  impression  that  has  been  made  upon  it  by  the 
treatment  through  which  it  has  passed.  The  preparation  of  a  fasciculus 
can  not  be  made  without  cutting  or  rending  the  parts,  mutilating  the 
nerves  of  supply,  and  totally  destroying  the  functions  of  the  arteries  and 
veins.  In  the  act  of  exsecting  such  a  fasciculus,  the  disturbance  im- 
pressed upon  it,  however  great  it  may  be,  is  never  fully  answered  to  by 
the  due  amount  of  contraction ;  for  with  the  destruction  of  the  vascular 
mechanism  there  are  no  means  of  removing  the  products  of  waste,  and  con- 
traction can  not  go  on  to  its  full  completion,  but  in  this  condition  the 
fasciculus,  placed  in  water,  gradually  gives  up  here  and  there  the  prod- 
ucts of  waste,  and  with  their  removal  the  opportunity  arises  for  the  re- 
maining muscular  elements  to  approach  one  another,  and,  finally,  com- 
plete contraction  ensues ;  a  contraction  not  due  to  the  immediate  action 
of  the  water,  but  to  the  change  impressed  upon  the  fasciculus  by  the  op- 
eration for  its  exsection. 

So  as  regards  disturbance  by  the  touch  of  foreign  bodies,  we  might 
Contraction  recall  those  numerous  instances  known  in  chemistry,  in  which 
by  touch,  decompositions  or  other  mechanical  results  are  brought  about 
in  a  similar  way.  The  different  compounds  which  undergo  explosive  de- 
composition by  the  lightest  friction  might  furnish  us  with  illustrations ; 
but,  in  this  instance,  the  effect  is  more  purely  mechanical,  and  arises  from 
the  forced  equilibrium  into  which  the  fasciculus  has  fallen  by  the  act  of 
exsecting  it  being  more  or  less  perfectly  overcome.  The  elements  of  a 
part  of  a  fasciculus  are  brought  by  that  touch  within  a  nearer  range  of 
one  another,  the  products  of  waste  which  had  failed  to  escape  because  of 
the  destruction  of  the  absorbent  function  of  the  veins  are  pressed  aside, 
one  motion  gives  rise  to  another,  a  worm-like  action  spreads  here  and 
there  irregularly  through  the  length,  and  ends  in  a  final  contraction.* 

Connected  with  the  phenomena  described  in  the  preceding  paragraph 
is  that  general  rigidity  of  the  muscles  which  occurs  a  certain 

Rigor  mortis.      .  °  -,    ,  , 

time  after  death,  and  hence  known  as  rigor  mortis.  This 
usually  commences  in  the  lower  jaw  and  neck,  invading  next  the  upper 
extremities,  and  reaching  eventually  the  lower  ones.  After  continuing 
for  a  period  longer  in  proportion  to  the  lateness  of  its  beginning,  relaxa- 
tion ensues,  the  parts  being  affected  in  the  same  order  as  they  were  made 
rigid.  The  rigor  mortis  sometimes  begins  as  soon  as  ten  minutes  after 
death,  sometimes  it  is  postponed  as  long  as  seven  hours.  In  those  who 
have  died  of  chronic  diseases  it  occurs  and  ceases  very  quickly.  Both 
classes  of  muscles,  striped  and  unstriped,  are  affected  by  it,  and  when  it 
is  over  they  present  an  unresisting  and  lax  condition,  and  putrefactive 
change  presently  sets  in.  Even  after  cadaveric  rigidity  has  been  as- 


OF   STANDING  AND  WALKING.  453 

sumed,  the  contractile  power  of  muscles  may  be  restored  by  furnishing 
them,  through  a  suitable  arrangement,  arterial  blood;  for  this  fact  we 
are  indebted  to  Dr.  Brown- Sequard,  his  experiments  having  been  made 
both  upon  man  and  animals.  The  arterial  blood  employed  assumed, 
during  its  passage  through  the  limb  which  was  the  subject  of  the  trial, 
the  venous  character,  and  issued  of  a  dark  color.  This  restoration  of 
contractility  was  by  no  means  imperfect  or  transient ;  in  one  instance  it 
continued  for  two  hours. 

By  means  of  tendon  the  muscles  are  attached  to  the  skeleton,  which 
constitutes  the  solid  framework  of  the  system.  Operating  Connection  of 
thus  through  the  skeleton,  the  muscles  are  enabled  to  keep  muscle  for  lo- 
the  entire  body  in  the  erect  or  standing  position,  and  also  to  ° 
give  it  locomotion.  The  conditions  of  standing  and  locomotion  have  been 
well  studied  by  the  brothers  Weber,  the  following  being  a  brief  synopsis 
of  their  statements. 

In  man,  the  power  of  standing  implies  the  conservation  of  the  line  of 
direction  of  the  whole  body  within  the  narrow  basis  covered  by  „ 

mi  i  i  i  Of  standing. 

the  feet  and  between  them.  The  head  is  balanced  on  the  at- 
las so  nearly  under  its  centre  of  gravity  that  no  ligamentum  nuchse  is 
required,  as  in  the  case  of  other  animals,  to  prevent  it  from  falling  for- 
ward. Nevertheless,  a  forward  motion  can  be  executed,  amounting  to 
about  75  degrees  from  the  perpendicular,  and  a  lateral  motion  right  and 
left  of  from  45  to  50  degrees.  In  standing,  the  weight  of  the  entire  body 
is  transmitted  perpendicularly  to  the  feet.  These  rest  on  the  heel  and 
the. fore  ends  of  the  metatarsal  bones,  especially  of  the  great  and  little 
toes,  and  on  the  points  of  the  toes.  The  general  centre  of  gravity  of  the 
entire  body  is  a  little  above  the  transverse  axis  connecting  the  heads 
of  the  thigh  bones,  and  for  equilibrium  to  be  maintained,  a  perpendicular 
line  drawn  from  this  centre  must  always  fall  within  the  basis  inclosed  by 
the  contour  of  the  feet. 

Even  in  the  most  perfect  condition  of  rest  that  we  can  assume  while 
maintaining  the  standing  position,  a  great  many  separate  muscular  acts 
are  necessarily  required.  Apart  from  those  little  voluntary  changes 
which  are  incessantly  occurring,  the  rhythmic  action  of  the  muscles  in- 
volved in  respiration,  especially  those  of  the  abdominal  walls,  is  perpet- 
ually changing  the  position  of  the  centre  of  gravity,  and  therefore  those 
muscles  which  are  employed  in  keeping  the  spine  erect  are  obliged  to 
assume  an  antagonizing  rhythmic  action.  This  is  at  once  the  reason  of 
the  fatigue  we  experience  in  long  standing,  and  of  the  difficulty  which 
infants  encounter  in  their,  attempts  to  maintain  the  erect  position. 

In  walking,  the  legs  act  like  a  pair  of  pendulums.     The  head  of  the 
thigh  bone,  which  is  their  centre  of  motion,  is  held  in  its  sock- 
et, not  by  muscular  exertion,  nor  by  its  ligamentous  arrange- 


454  OF.  RUNNING. 


merits,  but  by  the  pressure  of  the  air,  a  fact  that  may  be  proved  by  very 
simple  experiments.  If  the  pressure  of  the  air  be  removed,  as  in  an  ex- 
hausted receiver,  spontaneous  dislocation  ensues.  The  trunk  of  the  body 
is  like  a  rod  balanced  on  an  axis  passing  through  the  hip  joints,  and  ad- 
vancing with  the  movement  of  the  legs  like  a  rod  balanced  on  the  tip  of 
the  finger.  It  is  inclined  forward  or  backward  in  correspondence  with 
the  motion  or  with  the  resistance  of  the  wind ;  if  the  wind  blows  in  front, 
we  lean  forward;  if  behind,  we  lean  backward;  the  angle  of  inclination  be- 
ing in  proportion  to  its  force.  In  walking  there  are  two  distinct  periods : 
the  body  is  first  poised  on  one  of  the  limbs,  and  then  rests  for  a  moment 
on  both.  The  advancing  limb  swings  like  a  pendulum,  bending  at  the 
knee  so  as  to  be  shortened  one  ninth ;  the  other  straightening  at  the  knee 
and  hip  joint,  and  so  pushing  the  pelvis  and  trunk  forward  to  be  received 
on  the  limb  that  has  just  advanced.  It  is  only  in  slow  walking  that  the 
whole  arc  of  motion  is  swung  through,  the  time  occupied  being  two  thirds 
of  a  second.  In  quick  walking  and  running  only  half  a  vibration  is  ac- 
complished, and  this  in  half  a  second  of  time.  In  slow  walking  each  foot 
rests  upon  the  ground  one  third  of  a  second.  The  longest  step  made  is 
half  the  entire  span  of  the  two  extremities.  To  prevent  swaying  from 
side  to  side,  the  arms  swing  with  the  legs. 

In  running  there  is  a  moment  when  both  feet  are  off  the  ground  at 
once,  and  the  body  actually  projected  into  the  air.     In  walk- 
''  ing  there  is  a  moment  when  both  feet  are  on  the  ground  to- 
gether, the  one  not  being  raised  till  the  other  is  planted.     In  running  the 
steps  are,  on  an  average,  twice  as  long  as  in  walking  ;  and  the  number 
of  steps  made  in  a  given  time  in  running  and  walking  respectively  is  as 
3  to  2. 


HUMAI  PHYSIOLOGY. 


BOOK   SECOND. 


DYNAMICAL  PHYSIOLOGY. 

COURSE  OF  LIFE. 

CHAPTER  I. 

OF  THE  PRINCIPLE  OF  ORGANIZATION,  OR  PLASTIC  POWER. 

Remarks  on  the  Subdivision  of  Physiology. 

Career  of  an  Organic  Form. — Three  Modes  of  Development. 

Inquiry  respecting  the  special  Principle  of  Organization. — Illustration  from  the  Growth  of  a  Plant 
in  Darkness  and  Light. — Inference  respecting  Plastic  Power :  its  Nature  and  Properties. — 
Of  the  ordinary  Growth  of  a  Plant,  and  the  Sources  from  which  its  Materials  are  derived. 

Relation  of  all  Organisms  to  each  other. 

Correction  of  the  Doctrine  of  a  Plastic  Power,  from  Considerations  regarding  the  Individuality 
of  a  Plant. — Plants  are  Operations,  not  Individuals.— Physical  Illustration  of  this  View. 

Conclusion  respecting  the  Nature  of  the  Plastic  Power :  that  it  is  a  continued  Manifestation  of  an 


REGARDING  physiology  as  a  branch  of  natural  philosophy,  I  have  been 
led  in  this  work  to  introduce  the  methods  of  considering  it  Divisions  of 
which  are  familiar  to  writers  on  mechanics ;  for,  as  there  are  physiology, 
two  distinct  divisions  of  that  subject,  according  as  we  treat  of  the  equi- 
librium or  the  motion  of  inorganic  bodies,  so  likewise  there  must  be  in 
physiology  a  statical  and  dynamical  branch,  the  one  including  the  con- 
ditions of  equilibrium  of  an  organized  form,  the  other  those  of  its  devel- 
opment— development  being  no  more  than  its  motion. 

If  we  establish  this  subdivision  in  physiology,  similar  advantages  will 
doubtless  be  obtained  for  this  science  as  those  which  so  Advantages  of 
quickly  accrued  to  mechanics  after  Galileo  had  formally  in-  this  division. 
troduced  the  same  partition  therein.  Moreover,  in  this  case  there  are 
collateral  reasons  not  applying  to  that.  Whatever  may  be  the  views 
which  the  advance  of  science  causes  us  to  take  of  the  various  functions 
maintaining  a  living  animal  in  its  normal  state — whatever  may  b£  the 


456  CAREER  OF  AN  ORGANIC  FORM. 

general  conception  we  entertain  of  the  nature  of  its  equilibrium,  it  is 
scarcely  possible  to  present  the  subject  in  a  manner  that  will  coincide 
with  the  diversified  views  of  the  profession.  It  is  almost  exclusively 
with  statical  physiology  that  the  physician  has  to  deal.  The  healthy 
and  diseased  states  of  the  apparatus  for  digestion,  absorption,  respira- 
tion, circulation,  innervation,  etc.,  are  the  things  with  which  he  is  con- 
cerned. It  is  respecting  these  that  his  mind  is  filled  with  the  early  prej- 
udices of  his  education,  and  that  his  social  necessities  compel  him  to  ex- 
press with  decision  opinions  unsuited  to  a  close  philosophical  examina- 
tion. He  is  to  be  pardoned  for  the  mystification  which  circumstances 
oblige  him  to  cast  upon  the  subjects  of  his  study ;  for  resorting  to  the 
vital  principle  as  an  explanation  of  his  difficulties  ;  and  for  throwing  upon 
the  nervous  system  the  burden  of  every  thing  for  which  the  imperfect 
state  of  physiology  does  not  enable  him  to  account.  He  is  not  to  be 
blamed  that  the  circumstances  under  which  he  is  placed  compel  him  to 
appear  to  know  more  socially  than  he  actually  does  know  philosophically ; 
and  where,  under  such  a  false  position  of  things,  men  have  been  spend- 
ing their  lives,  it  is  not  at  all  extraordinary  that  they  should  resist  any 
attempt  at  a  reformation  which  strikes  at  the  very  existence  of  the  doc- 
trines they  have  adopted,  and  to  which  they  stand  committed.  The  old 
physician  must  have  his  vital  principle  and  his  nervous  agent,  or  he 
must  begin  the  alphabet  of  his  studies  again.  If,  therefore,  statical  phys- 
iology stood  alone,  it  must  depend  for  its  progress  in  the  gradual  removal 
of  error  and  introduction  of  truth  upon  one  generation  of  physicians  suc- 
ceeding another  ;  but,  fortunately,  there  is  a  circumstance  which  aids  it 
in  this  march,  for  the  great  branch  on  which  we  are  now  entering  pre- 
sents connections  and  considerations  of  a  more  purely  philosophical  kind; 
free,  at  all  events,  from  the  entanglements  of  professional  interests.  Ca- 
pable of  being  treated  in  the  rigid  manner  of  the  positive  sciences,  and  re- 
moved, by  reason  of  the  nature  of  the  topics  with  which  it  is  concerned, 
from  the  strifes  of  medical  sectarianism,  this  noble  subject  can  develop 
itself  in  silence,  without  disturbance  and  without  restraint ;  and  yet  such 
an  advance  can  not  take  place  without  compelling  a  reflected  effect  to 
ensue  in  statical  physiology,  and  hastening  the  time  when,  by  the  united 
consent  of  all  physicians,  it,  too,  will  be  cleared  from  every  mystification, 
and  brought  within  the  pale  of  exact  and  positive  science. 

In  the  preceding  book  we  have  investigated  the  conditions  of  the 
Career  of  an  or-  equilibrium  of  the  animal  mechanism:  in  this,  therefore,  we 
game  form.  have  ^Q  ftQ&i  of  its  motion  or  career.  Indeed,  we  might  gen- 
eralize our  expression,  and  include  the  vegetable  along  with  the  animal, 
for  the  two  are  so  inseparably  connected  that  we  can  not  speak  of  the 
one  without,  at  the  same  time,  dealing  with  the  other.  Viewed  as  re- 
spects, its  motion  or  career,  an  organism  presents  us  with  the  striking 


GEOMETRICAL  MODES  OF  DEVELOPMENT.  457 

fact  that  it  passes  through  a  definite  series  of  changes.  Commencing  at 
first  as  a  simple  cell,  to  which  what  might  be  termed  a  momentum  of  de- 
velopment has  been  imparted,  it  assumes  one  form  after  another  in  suc- 
cession, but  is  ever  ready,  like  the  moving  bodies  of  mechanics,  to  obey 
the  impulses  which  extraneous  forces  may  impress  upon  it.  Properly 
speaking,  we  can  never  say  of  an  organized  being  that  it  is  in  a  condi- 
tion of  rest.  In  truth,  it  is  always  in  motion.  It  has  a  past  and  a  fu- 
ture— coming  from  one  state  and  going  to  another ;  and  though,  to  use 
the  language  of  mechanics,  the  inertia  that  it  has  at  any  moment  must 
tend  to  continue  it  in  the  state  at  which  it  is  then  found,  since  it  varies 
by  degrees  from  one  condition  to  another,  we  are  obliged  to  look  upon  it 
in  these  variations  just  as  we  should  upon  an  inorganic  mass  under  sim- 
ilar circumstances,  and,  guided  by  the  incontrovertible  law  of  physics, 
that  (jyery  change  of  motion  is  to  be  attributed  to  the  influence  of  a  force, 
we  must  impute  its  passage  from  state  to  state  to  the  intervention  of  a 
like  agency.  In  this  respect,  the  career  of  an  organic  combination,  in  its 
two  conditions  of  maintaining  for  a  time  a  similarity  or  passing  through 
metamorphoses,  presents  a  general  analogy  to  the  uniform  rectilinear,  and 
to  the  varied  motion  of  mechanics. 

As  we  have  just  remarked,  the  most  elementary  organic  combination 
appears  to  be  a  simple  cell.  This,  under  circumstances  Tllree 
which  we  shall  presently  consider,  may  pass  into  develop-  rical  modes  of 
ment  by  multiplication  in  three  different  ways,  geometrical- 
ly distinct.  Its  development  may  be  in  one,  two,  or  three  dimensions — 
linear,  superficial,  or  solid.  As  illustrations  may  be  offered  the  proto- 
coccus,  which  is  a  simple  cell ;  the  linear  conferva?,  consisting  of  a  row 
of  cells  which  perpetually  undergo  terminal  extension,  the  line  becoming 
longer  and  longer  as  development  of  new  cells  at  the  end  goes  on ;  the 
ulvas,  in  which  increase  takes  place  simultaneously  in  length  and  breadth ; 
and  any  of  the  higher  forms,  which  grow  simultaneously  in  length, 
breadth,  and  thickness.  Whatever  the  manner  of  development  may  be, 
or  whatever  the  condition  presented  as  the  combination  passes  from 
phase  to  phase,  no  doubt  can  be  entertained  that  it  takes  place  in  conse- 
quence of  the  agency  of  forces  which  are  acting  under  definite  laws ;  and 
though,  even  in  the  case  of  organisms  low  in  the  series,  a  geometrical 
definition  of  their  form  is  impossible,  this  is  because  of  the  imperfection 
of  our  knowledge,  and  is  no  kind  of  indication  that  there  has  been  any 
irregularity  or  wantonness  of  play  in  the  forces  at  work. 

Asserting  thus  in  the  broadest  manner  the  influence  of  physical  forces 
over  development,  and  seeing  that  dynamical  physiology  must  inquiry  into 
be  committed  to  those  conditions,  and  those  alone,  which  are  the  existence 
universally  recognized  in  positive  science,  I  shall  proceed,  in  priLlpJe'of 
this  chapter,  to  set  forth  the  views  we  entertain  respecting  the  °rsanization. 


458  GERMINATION   OF   A   SEED. 

existence  and  nature  of  a  special  principle  of  organization.  The  conclu- 
sions at  which  we  shall  arrive,  though  apparently  very  different  from 
what  we  might  have  expected,  are  the  necessary  consequences  of  the 
physical  doctrine. 

It  may,  perhaps,  aid  the  reader  if  I  give,  at  the  outset,  a  synopsis  of 
Outline  of  the  ^e  argument.  Selecting  as  a  general  illustration  the  famil- 
argument.  iar  case  Of  the  germination  of  a  seed  and  the  growth  of  a 
plant,  we  shall  investigate  the  results  of  growth,  in  light  and  darkness, 
with  their  attendant  phenomena.  From  this  we  shall  draw  apparent  ev- 
idence of  the  existence  of  a  special  principle  of  organization,  or  plastic 
power,  and  ascertain,  in  a  general  way,  its  functions ;  but,  from  an  ex- 
amination of  the  attitude  in  which  the  resulting  organism  stands,  as  re- 
spects its  individuality,  we  shall  learn  to  correct  that  view,  and  reach  the 
final  conclusion  that  that  plastic  power  is  not  an  agent,  but  a  condition 
of  things,  the  result  or  the  manifestation  of  antecedent  physical  influ- 
ences. 


Every  living  being  springs  from  a  germ.  The  animal  and  vegetable 
Primordial  kingdoms  present  us  with  numberless  forms,  differing  from  one 
cel1-  another  in  aspect,  in  construction,  and  in  function  ;  but  the  or- 

igin of  all  is  the  same — a  cell  or  vesicle,  which,  under  the  influence  of 
external  circumstances,  develops  into  a  determinate  shape. 

A  seed  may  be  kept  in  a  dry  place  for  many  years  without  undergo- 
ing any  visible  change,  or  losing  its  power  of  germination.  It  may  be 
exposed  to  all  the  annual  variations  of  temperature  occurring  in  the  dif- 
ferent seasons ;  it  may  have  the  free  access  of  atmospheric  air.  Its  vi- 
tality is  dormant ;  there  is  no  attempt  at  evolving  its  parts. 

But  if  some  water  be  supplied,  and  a  certain  degree  of  dampness  be 
Germination  thereby  communicated,  the  seed  does  not  fail,  as  soon  as  the 
of  a  seed.  temperature  reaches  that  of  a  summer's  day,  to  germinate. 
Under  the  influence  of  air,  heat,  and  moisture,  the  embryo  consumes  the 
nourishment  stored  up  for  it  in  the  seed,  a  gradual  unfolding  of  its  parts 
ensues,  a  root  is  put  forth,  a  stem  rises  from  the  ground,  and  leaves 
make  their  appearance :  so  heat,  air,  and  water  have  enabled  the  seed  to 
become  a  plant. 

These  physical  agents  are  not,  however,  sufficient  to  carry  the  growth 
Effects  of  sun-  forward  to  its  full  extent.  Another  is  essential :  it  is  light ; 
light.  for  if  growth  be  conducted  in  darkness,  heat,  air,  and  water 

can  not  cause  the  young  plant  to  add  any  thing  to  its  substance.  It  is 
feeding  on  the  seed.  Indeed,  when  the  experiment  is  carefully  made,  it 
is  found  that  there  is  an  actual  loss  of  substance,  the  resulting  plant,  if 
dried,  weighing  less  then  than  the  dry  seed  from  which  it  came. 


CONSUMPTION  OF  LIGHT  BY  PLANTS.  459 

In  a  dark  place,  then,  it  is  possible  for  a  seed  to  grow,  but  it  grows  in 
a  certain  way,  and  only  to  a  certain  extent.  Its  stem  and  its  leaves  are 
of  a  sickly  yellowish  hue:  exposure  to  the  sunshine  soon  produces  a 
green  color  in  these  parts,  and  the  weight  of  the  plant  increases.  Growth 
in  darkness  leads  to  one  result,  and  growth  in  the  sunshine  to  another. 

From  these  facts  it  therefore  might  appear,  from  a  superficial  considx 
eration  of  the  thing,  that  the  development  of  a  plant  depends  partiai  infer- 
on  two  distinct  conditions — an  innate  power  which  resides  ence  respecting 

-T  1,1  ,-  P-I.-I-I  T       the  existence 

in  the  germ,  by  the  action  of  which  the  matters  previously  ofapiastio 
stored  up  in  the- seed  by  the  parent  plant  are  regrouped,  and  P°wer- 
so  arranged  as  to  constitute  a  new  organization ;  but  this  power  does  not 
extend  tg  the  obtaining  of  new  material;  it  is  only  a  power  of  arrange- 
ment— a  PLASTIC  POWER.     Whatever  new  material  is  required  must  be 
furnished  by  a  totally  distinct  agency,  the  sunlight;  and  just  as  the 
plastic  power  can  not  collect,  the  sunlight  can  not  arrange.     Each  has 
its    own   sphere   of  duty.     The   one  gives   the   substance,  the   other 
moulds  it. 

Every  flowering  plant,  no  matter  how  humble  it  may  be,  is,  then,  a  rep- 
resentative of  the  action  of  these  double  influences,  and,  when  Consumption 
properly  considered,  may  well  extend  the  views  we  ought  to  yegetabie* 
entertain  of  the  system  of  nature.  The  supplying  or  furnish-  development, 
ing  agent,  the  light,  comes  from  a  star  which  is  at  a  distance  of  almost  a 
hundred  millions  of  miles,  and  is  the  pivot  of  all  the  planetary  motions. 
Without  this  extraneous,  this  foreign  force,  the  whole  surface  of  the  earth 
would  be  a  desolate  waste,  presenting  no  semblance  of  life.  The  leaf, 
the  flower,  the  bud,  the  stem,  the  root,  are  all  made  of  substance  that  has 
been  given  by  the  sun,  derived,  it  is  true,  from  one  of  the  constituents 
of  the  air,  but  forced  to  take  on  the  special  state  which  suits  the  needs 
of  the  plastic  power  by  that  distant  agent ;  and,  in  order  for  this  to  oc- 
cur, it  is  plain,  from  mechanical  considerations,  that  there  must  have  been 
an  expenditure  of  power,  or  of  the  acting  principle  itself,  for  light  can 
not  produce  these  effects  without  losing  its  own  peculiar  form.  For  the 
decomposition  of  a  given  weight  of  carbonic  acid,  and  the  formation  of  a 
given  weight  of  gum,  a  fixed  and  invariable  quantity  of  light  is  required ; 
just  as  it  is  necessary,  in  moving  a  mass  of  a  certain  weight,  to  expend  an 
equivalent  and  definite 'force.  So  the  substance  of  which  plant-organs 
consist  has  been  brought  into  an  available  state  by  the  consumption  of 
a  definite  quantity  of  light— perhaps  its  incorporation,  under  some  other 
form,  in  the  resulting  mass.  It  may  be  pent  up  and  imprisoned  in  the 
organic  structure  for  any  imaginable  time,  even  for  centuries,  but  is  ever 
ready  to  resume  its  primitive  state  when  favorable  circumstances  exist. 
The  coal-fields  which  furnish  us  with  fuel  are  the  remains  of  primeval 
forests  which  grew  in  the  ultra-tropical  climate  of  the  secondary  times, 


460  NATURE  OF  THE  PLASTIC  POWER. 

and  the  light  and  heat  we  derive  from  them  are  the  same  that  came  from 
the  sun  in  those  ancient  days. 

If,  then,  our  earth  does  not  possess  in  herself  the  power  of  sustaining 
is  the  plastic  tne  varied  forms  of  vegetable  life,  but  borrows  it  from  an  ex- 
power  a  uni-  traneous  source ;  if  light,  in  producing  these  effects,  never 
fiSagenV  undergoes  destruction,  but  only  modifies  its  state — for  nei- 
like  the  ether?  £her  force  nor  matter  can  be  annihilated,  though  they  may  be 
changed — what  shall  we  say  of  the  plastic  power  which  we  have  thus 
assumed  to  reside  in  the  germ,  the  co-worker  with  the  luminous  agent  ? 
Does  their  partnership  in  action  indicate  a  resemblance  in  position  or  na- 
ture ?  If  the  one  consists  of  motion  arising  in  an  ethereal,  intangible,  and 
weightless  medium,  diffused  throughout  the  universe,  may  we,  suppose 
that  the  other  is  the  manifestation  of  a  similarly  diffused  principle? 
There  is  no  necessity,  as  many  have  thought,  to  impute  to  the  first-crea- 
ted germ  a  formative  power  for  all  its  successors,  as  though  whatever 
force  or  qualities  they  possess  were  originally  concentrated  and  included 
in  it.  It  is  possible  that  countless  millions  of  organic  beings  may  have 
originated  from  one  primordial  germ,  just  as  we  see  an  extensive  confla- 
gration originating  from  a  single  spark. 

That  such  a  plastic  principle  exists  has  long  been  admitted  by  philos- 
ophers, both  speculative  and  experimental.  It  is  a  doctrine  which  seems 
to  have  arisen  in  the  infancy  of  human  knowledge,  and  is  to  be  met  with 
in  almost  all  the  old  Asiatic  and  European  systems.  The  archeus  and 
soul  of  the  world  of  the  alchemists  were  only  the  reproduction  of  a  very 
ancient  idea.  The  term  "  vital  spark"  was  once  something  more  than 
a  mere  metaphorical  expression ;  and,  indeed,  there  is  a  classic*  noble- 
ness in  the  thought  which  recognizes  a  universal  spirit  diffused  every 
where.  In  different  countries  and  by  different  authors,  the  nature  and 
function  of  this  principle  are  variously  represented ;  imperfect  concep- 
tions of  what  is  so  significantly  but  briefly  set  forth  in  the  opening  words 
of  the  Sacred  Scriptures,  which  plainly  recognize  the  true  conditions  un- 
der which  all  vegetable  organisms,  arose — formless  matter,  the  sunlight, 
and  a  brooding  spirit. 

I  shall  continue  to  speak  of  this  principle  under  the  designation  of  the 
plastic  power,  because  that  expression  points  out  aptly  the  function  dis- 
charged, and  to  assume  that  all  those  organisms  which  possess  the  qual- 
ity of  converting  inorganic  bodies  into  organic  structures  do  so  under  the 
double  influence  of  light  and  of  this  interior  principle.  This,  of  course, 

Principio  coelum  ac  terras  camposque  liquentes, 

Lucentemque  globum  Lunaa,  Titaniaque  astra, 

Spiritus  intus  alit,  totamque  infusa  per  artus 

Mens  agitat  molem,  et  magho  se  corpore  miscet. 

Inde  hominum  pecudumque  genus  vitseque  volantum, 

Et  quae  marmoreo  fert  monstra  sub  aequore  pontus. — VIRG.  JEN.,  1  vi ,  724. 


ACTION  OF   DIFFERENT  RAYS.  461 

includes  nearly  all  vegetable  forms,  for  we  may  leave  out  of  considera- 
tion the  fungi,  a  group  which  stands  intermediately  between  plants  and 
animals.  The  distinctive  character  of  a  plant  is  to  form,  from  carbonic 
acid  of  the  air,  solid  organic  structures.  The  distinctive  character  of  an 
animal  is,  by  the  oxidizing  processes  going  on  in  it,  to  restore  the  or- 
ganic bodies  which  have  served  it  as  food  to  their  original  formless  state. 
The  group  referred  to  differs  from  true  plants  in  feeding  on  matter  al- 
ready organized,  and  breathing  like  animals.  It  therefore  does  not  re- 
quire the  influence  of  light  to  collect  material  for  it,  and  bring  it  to  the 
proper  state.  In  the  development  of  this  group  the  plastic  principle  is 
alone  concerned. 

Since  the  sunlight  is  composed  of  many  differently  colored  rays  and 
different  principles,  it  becomes  an  interesting  inquiry  which  Powe*  of  dif 
of  these  is  the  immediate  agent  in  ministering  to  the  nutri-  ferent  colored 
tion  of  plants.  In  1843,  by  causing  plants  to  effect  the  de-  raysoflisht- 
composition  of  carbonic  acid  in  the  prismatic  spectrum,  I  found  that  the 
yellow  is  by  far  the  most  effective,  the  relative  power  of  the  various  col- 
ors being  as  follows : 

Yellow,  Blue, 

Green,  Indigo, 

Orange,  Violet. 
Bed, 

My  experiments  on  the  production  of  hydrochloric  acid  by  the  direct 
union  of  chlorine  and  hydrogen  under  the  influence  of  light,  Phenomena  of 
both  artificial  and  solar,  and  also  on  the  decomposition  of  ihe  action  of 
pe'roxalate  of  iron,  from  which  carbonic  acid  is  readily  disen-  growth  of  & 
gaged,  conclusively  establish  the  fact  that  the  primary  con-  Plants- 
dition  essential  for  the  chemical  action  of  light  is  the  absorption  of  some 
particular  ray.     If  the  physical  condition  of  substances  otherwise  easily 
decomposable  is  such  that  they  transmit  light  without  absorbing  any,  no 
chemical  change  ever  ensues  in  them,  and  the  same  condition  obtains  in 
cases  of  combination.     Thus  oxygen  and  hydrogen  can  not  be  made  to 
unite,  even  by  the  most  intense  radiation,  because  neither  of  them  ex- 
ert any  absorptive  action ;  but  chlorine  and  hydrogen  unite  with  energy, 
because  the  chlorine  absorbs  the  indigo  ray. 

The  same  experiments  prove  that  the  amount  of  decomposition  or  oth- 
er work  done  by  light  is  always  proportional  to  its  quantity ;  hence,  by 
the  aid  of  converging  mirrors  and  lenses,  chemical  changes  can  be  ac- 
complished with  great  rapidity.  These  instruments,  however,  when  even 
of  the  largest  size,  are  unable  to  produce  any  other  effect  than  would  be 
brought  about  by  a  feebler  ray  if  applied  sufficiently  long.  The  great- 
ly increased  intensity  of  light  which  they  can  present  does  not  enable  us 
either  to  bring  about  combinations  or  decompositions  of  substances  which 


462  PLANTS    LIBERATE   OXYGEN. 

are  unacted  upon  by  rays  of  a  more  moderate  brilliancy,  for  the  general 
rule  under  which  the  chemical  action  of  light  occurs  is,  the  amount  of 
chemical  change  is  as  the  quantity  of  light  absorbed. 

These  facts  are  of  importance  in  all  discussions  respecting  the  prim- 
itive formation  of  organic  matter  by  plants.  Guided  by  them,  we  infer 
that,  though  vegetation  may  greatly  differ  in  its  luxuriance  in  different 
climates  of  the  globe,  the  manner  of  action  of  the  light  is  always  the 
same.  Nothing  is  gained  under  the  brilliancy  of  the  tropical  skies  be- 
yond a  shortening  of  the  time  required  for  the  accomplishment  of  a  given 
amount  of  work.  No  substances  are  there  decomposed,  even  in  the  or- 
ganisms of  plants,  which  could  not  equally  well  be  decomposed  by  the 
feebler  light  of  more  temperate  climates,  only  in  these  it  would  demand 
more  time.  The  oils  and  other  substances,  almost  or  quite  free  from 
oxygen,  which  abound  in  the  plants  of  the  torrid  zone,  are  not  excep- 
tions to,  but  illustrations  of,  the  doctrine  here  set  forth. 

It  is  proper  here  to  correct  the  statement  which  is  usually  made  by 
it  is  not  the  vegetable  physiologists,  that  the  decomposition  of  carbonic 
green  parts  of  aci(j  fty  plants  is  accomplished  by  their  srreen  parts.  A 

plants  which  J  ,  *  £  •    j      j  I.-  i.    t, 

decompose  car-  plant  which  has  been  etiolated,  or,  indeed,  one  which  has 
bonic  acid.  been  raised  from  a  seed  in  total  darkness,  when  brought  into 
the  sunshine,  decomposes  carbonic  acid,  liberates  oxygen,  and  its  pale 
and  sickly  leaves  presently  turn  green.  This,  therefore,  demonstrates 
that  the  green  portions  are  not  the  seat  nor  the  origin  of  the  decomposi- 
tion, but  are,  properly  speaking,  its  effect. 

Thus,  under  the  influence  of  sunshine,  the  leaves  of  plants  decompose 
Plants  liberate  carbonic  acid,  liberate  its  oxygen,  which,  for  the  most  part, 
oxygen.  escapes  into  the  atmosphere,  the  amount  of  gas  decomposed 

depending  primarily  on  the  quantity  of  light  supplied,  and  therefore, 
among  other  conditions,  on  the  surface  of  exposure  of  the  leaves,  and 
not  upon  their  thickness  or' mass.  But  I  found,  on  an  examination  of 
the  gas  thus  evolved,  that  it  is  never  pure  oxygen,  but  always  contains 
a  certain  though  variable  proportion  of  nitrogen.  From  this  it  follows 
that  a  part  of  the  oxygen  appertaining  to  the  carbonic  acid  is  appropri- 
ated for  the  uses  of  the  plant. 

Such,  in  a  general  way,  is  what  takes  place  in  the  daytime,  but  at 
night  the  process  is  to  a  certain  degree  inverted,  a  plant  absorbing  oxy- 
gen from  the  air,  and  yielding  carbonic  acid.  The  explanation  which 
Liebig  offers  of  this  state  of  things  is  doubtless  correct,  that  the  evolu- 
tion of  carbonic  acid  is  a  purely  physical  process,  and  the  absorption  of 
oxygen  due  to  the  chemical  action  of  the  various  deoxidized  bodies 
which  have  been  accumulating  during  the  day. 

As  respects  the  sources  from  which  the  various  constituents  of  the 
plant  organism  are  derived,  they  are  sufficiently  obvious.  The  carbon 


SOURCES  OF  THE  CONSTITUENTS   OF  PLANTS.  463 

may  doubtless  be  entirely  attributed  to  carbonic  acid,  ob-  sourcesfrom 
tained  either  directly  from  the  atmosphere  or  furnished  by  which  the  con- 
the  gradual  decay  of  humus  in  the  soil.     For  the  hydrogen  plant"  are  de- 
a  double  source  may  be  assigned  —  water  and  ammonia.  rived-  Ofcar- 
The  abundant  occurrence  of  resins,  oils,  fats,  in  which  this 


element  preponderates,  conclusively  establishes  the  fact  that 
the  supply  of  ammonia,  as  indicated  by  the  nitrogenized  compounds' 
which  have  been  formed,  is  insufficient  to  account  for  the  quantity  of  hy- 
drogen, and  for  which  there  would  appear  no  other  source  than  water  ; 
and  though  the  most  brilliant  light,  even  though  concentrated  by  a  pow- 
erful burning-glass,  can  not  alone  eifect  the  decomposition  of  this  liquid, 
there  will  be  no  difficulty  in  admitting  that  such  a  decomposition  does 
take  place,  when  we  recall  that  carbon  is  being  presented  in  what  might 
be  termed  its  nascent  state. 

Of  the  nitrogen  necessary  for  the  formation  of  the  protein  bodies  of 
plants,  it  is  generally  concluded  that  ammonia  is  the  only 
source,  and  that  these  organisms  do  not  directly  obtain  that 
element  from  the  atmospheric  air;  moreover,  it  occurs  apparently  to  a 
sufficient  extent  in  their  sap,  having  been  introduced  by  absorption 
through  the  roots.     As  essential  to  the  production  of  the  same  group 
of  bodies,  the  protein  substances,  both  sulphur  and  phosphorus  are  in- 
troduced through  the  same  channel,  from  the  soil,  as  sul-  of  sulphur  and 
phates  and  phosphates,  which  undergo  decomposition  and  phosphorus. 
deoxidation  within  the  organism,  so  as  to  yield  the  sulphur  and  phos- 
phorus in  an  unoxidized  state. 

We  can  not  overlook  the  saline  substances,  or  mineral  bodies,  which 
occur  in  different  parts  of  plants,  and  which  obviously  are  of  saline  sub- 
absolutely  essential  to  their  constitution.  The  circumstance  stances. 
that,  in  any  given  plant,  they  are  found  fixed  in  their  nature,  definite  in 
their  quantity,  and  deposited  in  determinate  regions,  is  sufficient  to  es- 
tablish that  conclusion.  As  is  very  well  known,  we  can  not  judge  of 
their  nature  or  condition  during  the  life  of  the  plant  from  the  aspect  they 
present  when  its  ash  is  examined.  Thus  those  which  have  been  exist- 
ing as  neutral  or  acid  salts  of  organic  acids  must  appear  in  the  ash  as 
carbonates  ;  and  though  it  has  been  established  that  basic  and  mineral 
substances  generally  will  to  some  degree  replace  one  another  —  nay,  that 
even  the  plant  itself,  by  generating  vegetable  alkaloids,  may  dispense 
with  bases  of  the  mineral  kind,  the  extent  to  which  this  can  be  carried 
is  as  yet  undetermined.  The  occurrence  of  sulphates  and  phosphates 
in  the  leaves  and  seeds,  and  wherever  organic  activity  has  to  be  dis- 
played, and  protein  bodies  are  found,  is  sufficient  to  establish  a  con- 
nection between  those  substances  and  the  neutral  nitrogenized  bodies, 
though  of  the  manner  in  which,  from  carbonic  acid,  water,  ammoniaj 


464  ACTION  OF  PLANTS   ON  THE  AIE. 

sulphates,  and  phosphates,  those  bodies  are  formed,  we  are  as  yet  alto- 
gether ignorant. 

By  some  chemists  it  has  been  supposed  that  the  decomposition  of  car- 
The  decompo-  bpnic  acid  by  plants  in  the  sunshine  is  not  instantaneously 
sition  of  car-  complete,  but  that  a  gradual  process  of  reduction  takes  place, 

bonic  acid  is       ,  ,          ,  ,       ••.,,••  i  v,,!      •  ,  -, 

not  partial,  but  the  carbon  losing  by  little  and  little  its  oxygen,  but  never, 
•total.  perhaps,  losing  it  all.     My  own  experiments,  previously  al- 

luded to,  which  show  that  the  quantity  of  oxygen  set  free  is  never  quite 
equal  to  that  of  the  carbonic  acid  consumed,  have  been  used  in  support 
of  this  view.  But  this,  I  think,  is  an  interpretation  which  they  will 
scarcely  bear.  There  are  many  facts  connected  with  the  chemical  action 
of  light  which  might  be  cited  as  offering  abundant  proof  that  the  decom- 
position in  question  is,  on  the  contrary,  instantaneous  and  complete,  and 
in  that  I  am  led  to  believe  really  consists  the  primary  function  of  the 
light,  the  carbon  thus  obtained  being  subsequently  employed  in  accom- 
plishing the  decomposition  of  water,  and  other  processes  of  reduction 
known  to  go  on  in  the  vegetable  organism,  but  with  which,  under  the 
circumstances  of  the  case,  it  is  impossible  that  the  sunlight  should  be  di- 
rectly concerned.  I  separate  as  distinct  factors  in  the  life  of  a  plant 
the  obtaining  of  carbon  from  the  air,  which  is  accomplished  by  the  influ- 
ence of  an  external  agent,  and  the  moulding  or  modifying  it  with  other 
ingredients  into  organized  material,  which  we  have  thus  far  imputed  to  a 
plastic  power  in  the  plant  itself,  and  respecting  which  more  will  be  pres- 
ently said.  Free  carbon  once  obtained,  we-  can  easily  conceive  that  all 
other  operations  of  reduction  may  follow,  and  that  this  division  of  the 
action  of  plants  into  two  distinct  stages  or  factors,  as  we  have  just  term- 
ed them,  is  not  a  mere  speculation,  but  represents  what  in  reality  occurs, 
will  perhaps  be  admitted  on  recalling  what  has  been  remarked  on  growth 
in  the  sunshine  and  in  darkness  respectively. 

As  a  summary  of  the  action  of  vegetation  on  the  air,  it  is  on  all  hands 
Summary  of  admitted  that  plants  tend,  by  the  removal  of  carbonic  acid 
SLfcforTthe  therefrom  and  the  return  of  oxygen  thereto,  to  compensate  for 
atmosphere,  the  disturbance  occasioned  by  animals,  which  is  to  the  oppo- 
site effect.  In  this  way,  through  very  many  centuries,  the  same  percent- 
age constitution  of  the  atmosphere  is  maintained,  the  sum  total  of  veg- 
etable being  automatically  adjusted  to  the  sum  total  of  animal  life ;  auto- 
matically, and  not  by  any  interference  of  Providence ;  for  if  we  admit, 
what  has  been  conclusively  established  by  direct  experiment,  that  plants 
would  grow  more  luxuriantly  in  an  atmosphere  somewhat  richer  in  car- 
bonic acid  than  the  existing  one,  we  may  see  how  upon  this  condition  de- 
pends a  principle  of  conservation,  which  must  forever  retain  the  air  at  its 
present  constitution,  no  matter  how  animal  life  may  vary.  The  proofs 
that  are  sometimes  offered  that  there  has  been  no  change  in  this  respect 


CONDITIONS  OF  GROWTH.  465 

for  at  least  2000  years,  and  which  are  drawn  from  an  examination  of  the 
aerial  contents  of  vessels  said  to  have  been  obtained  from  Pompeii  or 
Herculaneum,  are  of  very  little  account.  We  have  only  to  recollect  how 
easily  diffusion  takes  place  through  crevices,  and  even  almost  invisible 
pores.  But  there  are  proofs  of  a  far  higher  order,  and  of  a  much  more 
general  kind,  which  might  be  brought  forward,  if  this  were  the  proper 
place,  establishing  beyond  all  possibility  of  contradiction  the  fact  that  in 
a  slow  manner,  through  countless  ages,  the  constitution  of  the  atmosphere 
has  changed,  and  that  now,  through  the  operation  of  conditions  which 
have  spontaneously  arisen,  it  has  come  into  a  condition  of  apparent 
equilibrium. 

When,  therefore,  a  seed  is  placed  in  the  ground  in  the  warm  season  of 
the  year,  the  germ  it  contains  develops,  and,  after  a  few  days,  makes  its 
appearance  as  a  young  plant  at  the  surface.  If  the  growing  structure  is 
examined  during  its  passage  through  the  soil,  it  presents  a  pale  yellow- 
ish aspect,  which  is  exchanged  for  a  bright  green  tint  as  soon  as  it 
escapes  from  its  confinement,  and  unfolds  itself  to  the  sunlight  and  the  air. 

From  the  first  moment,  until  the  green  color  is  assumed,  the  young 
plant  is  nourished,  as  we  have  seen,  at  the  expense  of  the  Infantile  and 
seed.     In  anticipation  of  this,  the  parent  had  laid  up  a  stock  adult  life  of 
of  nutritive  material.     On  this  the  embryo  draws,  consuming  Plantf- 
a  part  in  the  support  of  its  life,  and  incorporating  the  residue  in  its 
structure ;  but  as  soon  as  the  surface  of  the  soil  is  gained,  this  life  of  de- 
pendence ends ;  the  plant  weans  itself,  and,  abandoning  its  temporary 
support,  commences  to  collect  from  the  air  and  the  earth  tfie  materials  of 
which  it  is  to  consist.     Its  infantile  seed-life  has  closed ;  its  independ- 
ent aerial  life  has  begun. 

In  this  aerial  life,  which  is  the  mode  of  existence  destined  to  continue 
until  absolute  death  occurs,  the  two  essential  conditions  to  gumma    Of 
which  we  have  drawn  attention  are  recognized.     There  must  the  conditions 
be  a  steady  supply  of  material  for  the  building  up  of  the  °  grox 
growing  structures,  and  this  has  to  be  derived  from  external  sources. 
There  must  also  be  a  capability  of  so  grouping  or  moulding  the  material 
thus  acquired  that  the  various  parts  that  are  wanted — leaves  or  fruits, 
flowers  or  thorns,  may  be  made. 

The  manner  in  which  these  conditions  are  satisfied  presents  to  a  re- 
flecting mind  one  of  the  most  wonderful  examples  of  the  system  of  na- 
ture. We  have  already  shown  that  the  power  of  moulding  and  group- 
ing is  inherent  in  the  plant.  In  virtue  of  this,  while  it  was  yet  in  the 
ground,  and  therefore  in  the  dark,  the  germ  could  put  up  its  stem  and 
fashion  its  imperfect  leaves,  but  it  did  not  possess  any  power  to  gather 
nourishment  beyond  that  which  was  stored  up  in  the  seed,  and  had  that 
stock  been  exhausted  before  it  reached  the  surface,  it  must  have  died. 

GG 


466  RELATION   OF   ORGANIC    FORMS. 

We  have  also  shown  that  the  supply  of  new  material  is  always  fur- 
nished by  the  sun.  In  the  absence  of  his  rays  the  plant  may  organize, 
but  can  not  increase,  and,  indeed,  it  was  to  the  influence  of  light  that  the 
green  color  of  the  first  leaflets  was  due.  All  the  day  long,  and  with  the 
more  activity  as  the  day  is  brighter,  the  leaves,  which  are  the  collecting 
organs,  are  absorbing  material  from  the  air ;  they  cease  to  do  it  at  night. 
The  sunbeam  enables  them  to  take  from  the  air  carbon,  hydrogen,  and 
nitrogen.  They  feed  by  day  and  fast  at  night. 

Astronomers  say  that  the  sun  is  the  most  sublime  object  the  eye  of 
man  can  contemplate.  They  speak  of  his  prodigious  mass,  and  describe 
how  he  compels  the  planets  to  move  in  obedient  circles  around  him.  To 
the  physiologist  he  is  not  less  sublime.  The  most  insignificant  moss 
that  grows  on  the  wall  was  called  into  existence  by  his  heat,  and  is  daily 
fed  by  his  light.  The  sunbeam  is  the  finger  of  God. 

The  nutrition  of  plants  is  therefore  dependent  on  physical  causes. 
The  carbonic  acid  required  being  brought  to  them  by  aerial  currents,  oc- 
casioned partly  by  the  warming  influence  of  the  sun  on  their  leaves  and 
•partly  by  the  winds,  the  tendency  of  gases  to  diffuse  into  one  another 
aids  in  producing  the  same  result.  In  this  manner,  as  they  exhaust  the 
surrounding  air,  fresh  quantities  are  supplied,  the  separation  of  carbon 
from  it  being  brought  about  by  the  agency  of  the  yellow  rays.  The 
leaves,  also,  sometimes  follow  the  motion  of  the  sun,  or  present  themselves 
in  the  most  favorable  position  under  the  influence  of  the  indigo  rays. 

The  water  requisite  is  obtained  from  the  soil  by  the  spongioles  of  the 
roots.  With  *t  there  are  carried  into  the  interior  of  the  plant  the  saline 
and  inorganic  substances  necessary  for  its  structure.  These,  since  they 
are  often  of  sparing  solubility  in  water,  will  require  large  quantities  of 
that  liquid  to  effect  their  introduction  to  a  proper  amount.  During  the 
course  of  a  summer  there  may  pass  through  the  system  of  the  plant 
perhaps  many  hundred  times  its  weight  of  water — a  prodigious  amount 
when  the  phenomenon  is  considered  on  the  great  scale. 

Cuvier  speaks  of  the  inferior  organisms  as  furnishing  us  with  a  series 
Relation  of  or  °^  exPeriments  made  by  the  hand  of  Nature,  an  idea  often 
ganisms  to  quoted  and  often  admired,  but  which  is,  perhaps,  scarcely  con- 
each  other.  gistent  with  enlarged  conceptions  of  the  system  of  the  world. 
An  organism,  no  matter  how  high  or  low,  is  not  in  an  attitude  of  isola^ 
tion.  It  is  connected  by  intimate  bonds  with  those  above  and  those  be- 
neath. It  is  no  product  of  an  experimental  attempt,  which,  either  on  the 
part  of  Nature  or  otherwise,  has  ended  in  failure  or  only  partial  success. 

The  organic  series — an  expression  which  is  full  of  significance  and  full 
of  truth,  for  it  implies  the  interconnection  of  all  organic  forms — the  or- 
ganic series  is  not  the  result  of  numberless  creative  blunders,  abortive  at- 
tempts, or  freaks  of  Nature.  It  presents  a  far  nobler  aspect.  Every 


RELATION  OF  ORGANIC  FORMS.  467 

member  of  it,  even  the  humblest  plant,  is  perfect  in  itself.  From  a  com- 
mon origin,  a  simple  cell,  all  have  arisen :  there  is  no  perceptible  micro- 
scopic difference  between  the  primordial  vesicle  which  is  to  produce  the 
lowest  plant,  and  that  which  is  to  produce  the  highest ;  but  the  one,  un- 
der the  favoring  circumstances  to  which  it  has  been  exposed,  has  contin- 
ued in  the  march  of  development,  the  career  of  the  other  has  been  stop- 
ped at  an  earlier  point.  The  organic  aspect  at  last  assumed  The  forms  of 
is  the  strict  representation  of  the  physical  agencies  which  have  organization 

,  i         TT   j  .0.          *  •    j     i  •        depend  on 

been  at  work.  Had  these  for  any  reason  varied,  that  varia-  physical 
tion  would  at  once  have  been  expressed  in  the  resulting  form,  asents- 
which  is,  therefore,  actually  a  geometrical  embodiment  of  the  antecedent 
physical  conditions.  For  what  reason  is  an  offspring  like  its  parent, 
except  that  it  has  been  exposed,  during  development,  to  the  same  condi- 
tions as  was  its  parent  ?  Comparative  physiology  is  not  a  fortuitous  col- 
lection of  experiments.  Our  -noblest  conception  of  it  is  the  conception 
we  have  of  analytical  geometry,  and,  speaking  in  mathematical  language, 
each  member  of  the  organic  series  is  an  embodied  result  of  a  discussion 
of  the  equation  of  life  for  one  special  case.  Nay,  I  would  present  the 
whole  system  of  Nature  as  included  in  the  same  idea.  The  inorganic 
and  lifeless  combinations  which  are  all  around  us  are,,  to  my  mind,  in 
truth,  in  that  equation  of  life,  the  analogues  of  the  imaginary  solutions  of 
the  calculus.  • 

It  was  a  felicitous  thought  of  Descartes  that  we  may  represent  a  geo- 
metrical form  in  an  algebraical  equation,  and,  by  the  proper  Illustration  of 
consideration  and  discussion  of  such  an  expression,  determ-  the  relation  of 
ine  and  delineate  all  the  peculiarities  of  such  a  form ;  that  here  J£f? ™  £™8 
it  should  become  concave  and  there  convex,  here  it  should  analytical  ge- 
run  out  to  infinity,  there  have  a  cusp.  The  equation  determ- 
ines all  the  peculiarities  of  the  form,  and  enables  us  to  construct  it.  But 
if  the  original  conditions  are  inconsistent  with  one  another,  the  construc- 
tion can  not  be  fulfilled,  it  having  become  impossible.  In  the  same  man- 
ner are  all  living  and  lifeless  forms  related :  an  increase  in  the  value  of 
one  condition  carries  development  forward  in  one  direction,  and  increase 
in  the  value  of  another  condition  determines  development  in  another  way, 
and  these  variations  give  rise  in  their  succession  to  the  whole  organic 
series.  But  in  these,  as  in  the  other  case,  if  inconsistent  conditions  have 
existed,  their  presence  is  indicated  in  the  resulting  solution,  which  can 
not  be  constructed  as  an  organic  form,  but  is  represented  as  a  lifeless 
mass. 

"God  ever  geometrizes,"  ajid,  it  might  be  added,  ever  materializes. 
Every  organism  is  the  result  of  the  development  of  a  vesicle  under  given 
conditions,  carried  out  into  material  execution.  It  is  the  incarnation,  the 
embodiment,  the  lasting  register  of  physical  influences  ;  for,  if  such  Ian- 


468  NATUKE   OF   INDIVIDUALITY. 

guage  may  be  with  propriety  used,  the  consequences  of  the  action  of  nat- 
ural agents  do  not  remain  as  a  barren  idea  in  the  creative  mind,  but  are 
presented  as  a  material  and  tangible  result. 

Such  a  mathematical  conception  of  the  relations  of  the  various  forms 
around  us  obliterates  at  once  the  line  of  demarcation  which  natural  his- 
tory has  thus  far  vainly  attempted  to  define  with  correctness  between 
the  organic  and  inorganic  worlds.  In  the  system  of  creation  no  such 
boundary  exists ;  neither  does  one  exist  between  the  vegetable  and  ani- 
mal groups.  On  every  form,  all  existing  influences  have  exerted  their 
sway:  gravitation,  heat,  electricity;  the  result  is  the  issue  of  their  action. 
The  shape  of  any  great  mountain  is  thus  the  record  of  every  thing  that 
has  affected  its  mass  since  it  was  first  uplifted.  Its  ancient  peaks  are 
the  register  of  every  summer's  sun,  every  frost,  every  falling  rain,  every 
lightning  stroke.  It  is  what  it  is  because  of  them  ;  and  so  also  of  the 
lichen  which  unfolds  itself  on  some  favorable  spot  on  the  rock.  "Would 
it  be  there  at  all,  or  would  it  have  the  special  aspect  it  presents,  if  there 
was  not  a  due  proportion  of  sunshine,  a  proper  supply  of  moisture,  a 
suitable  temperature  ?  It  is  such  conditions  which  have  called  it  forth. 
It  is  what  it  is  because  of  them.  In  this  respect,  between  the  inorganic 
and  organic,  there  is  no  difference. 

The  preceding  elementary  examination  of  the  circumstances  under 
Correction  of  which  plants  grow  has  led  us  to  the  inference  that  in  their 
°_f  germ  there  resides  a  plastic  power  whose  function  it  is  to 
model  the  organic  matter,  as  it  is  furnished  by  the  sunlight, 
into  definite  shapes  or  organs.  We  now  proceed  to  correct  the  concep- 
tion we  have  thus  formed,  and  to  show  that  it  is  more  philosophical  to 
decline  the  idea  of  an  agent  and  to  accept  that  of  a  condition. 

Perhaps  the  most  simple  method  of  illustrating  this  idea  is  from  con- 
siderations connected  with  the  individuality  of  the  organisms  which  have 
thus  arisen.  Directing  their  attention  to  plants',  botanists  have  occupied 
themselves  in  endeavoring  to  determine  what  is  the  attitude  in  which 
Considerations  they  stand.  They  have  tried  to  find  out  wherein  the  indi- 
iSviduaiithe  "^duality  of  a  plant  consists,  for  this  question  of  individual- 
of  a  plant.  ity  lies  truly  at  the  basis  of  the  position  which  those  struc- 
tures occupy.  There  are  oaks  that  have  lasted  a  thousand  years,  but  are 
they  to  be  regarded  as  individuals  that  are  a  thousand  years  old  ?  Is 
not  such  a  tree  rather  like  a  nation,  a  collection  or  colony  of  individuals, 
the  individuality  belonging  to  each  bud,  to  each  leaf  it  has  borne ;  for 
there  is  a  close  analogy,  if  not  an  absolute  identity,  between  the  process 
of  development  of  a  seed  in  the  ground  and  of  a  bud  upon  a  branch ; 
both  have  their  infantile,  both  their  aerial  life.  The  leaves  of  the  oak, 
which  expand  in  the  spring,  fall  in  the  autumn.  Their  origin  and  du- 
ties are  connected  with  astronomical  events.  Each  annual  generation, 


NATURE   OF  INDIVIDUALITY.  469 

while  it  lasted,  carried  forward  all  the  functions  of  the  tree,  as,  in  a  na- 
tion that  may  have  endured  for  a  thousand  years,  each  generation  of  men 
has  borne  its  part  in  the  general  scheme,  and  made  provision  for  its  suc- 
cessors. The  individuality  therefore  lies  not  in  the  tree,  but,  perhaps, 
as  thus  far  considered,  should  be  referred  to  the  bud. 

But,  moreover,  when  we  consider  the  modes  by  which  a  tree  may  be 
propagated,  as,  for  instance,  in  the  horticultural  processes  of  budding  or 
grafting,  our  views  of  this  question  of  individuality  must  again  be  modi- 
fied. By  these  artificial  operations  an  original  stock  may  be  multiplied 
again  and  again,  and  each  of  the  plants  so  arising  is  undistinguishable  from 
any  other  that  may  have  come  in  the  same  way.  Setting  aside  the  inci- 
dental difference  that,  through  the  intervention  of  artificial  means,  the  buds 
from  which  two  such  plants  have  originated  have  been  brought  under  the 
condition  of  physical  independence  of  one  another,  the  one,  perhaps,  grow- 
ing in  America,  the  other  in  Europe,  is  there  any  absolute  and  essential 
difference  between  them  more  than  there  would  have  been  had  they  been 
permitted  to  remain  upon  the  parent  stock,  and  to  develop  themselves  into 
two  branches  thereof?  Such  facts  suggest  to  us  that  individuality  does 
not  belong  to  plants,  as  they  thus  present  themselves  to  us,  and  that 
perhaps  we  ought  to  assume  an  individuality  of  a  higher  order — a  race 
individuality,  as  it  were.  In  this  manner,  all  weeping  willows  in  Europe 
and  in  America  are  one  individual,  because  they  have  all  been  derived 
from  one  original  imported  Babylonian  stock ;  and  the  same  might  be 
said  of  every  one  of  our  cultivated  fruits.  But  of  these,  if  a  seed  be  plant- 
ed, the  general  aspect  of  the  resulting  growth  may  possibly  be  the  same 
as  that  derived  from  a  graft,  and  how  shall  we  then  make  a  distinction 
between  the  one  and  the  other?  for,  though  by  seed  development  the 
plant  may  chance  to  run  back  to  a  wilder  form  or  to  produce  a  new  va- 
riety, this  result  is  by  no  means  absolutely  necessary. 

From  similar  considerations,  some  physiologists  have  been  led  to  deny 
individuality  to  the  bud  and  the  seed,  and  to  refer  it  to  the  primary  cell ; 
but  here,  again,  precisely  the  same  difficulties  are  encountered.  A  cell 
may  multiply  itself  by  fissure  through  its  nucleus,  as  well  as  in  an  en- 
dogenous way ;  moreover,  cells  arise  from  granular  material.  Individu- 
ality, therefore,  except  it  be  that  of  a  lower  order,  can  not  be  attributed 
to  them,  and  the  question  of  the  determination  of  it  rests  precisely  where 
we  found  it. 

In  truth,  are  not  all  such  discussions,  in  their  very  nature,  illusory,  so 
long  as  we  have  no  more  definite  idea  of  the  term  individu-  The  idea  of  in- 
ality  ?  If  a  natural  philosopher  were  to  occupy  himself  with 
similar  discussions  respecting  the  flame  of  a  lamp,  he  too,  piahts. 
doubtless,  would  be  led  to  precisely  the  same  empty  conclusion.  He 
might  show  how,  in  such  a  flame,  there  are  separate,  well-marked  re- 


470         ANALOGY  BETWEEN  A  PLANT  AND  A  FLAME. 

gions,  some  of  which  were  present  at  the  first  moment  of  its  existence, 
and  remain  to  its  end,  as,  for  example,  the  blue  portion  which  is  at  its 
under  part.  He  might  show  how  every  one  of  these  flames  tends  to  as- 
sume a  definite  or  determinate  form — conical,  for  instance — and  proceed 
to  argue  that  this  is  the  result  of  the  interaction  of  external  causes,  as  the 
passage  of  currents  in  the  air,  and  some  interior  principle  or  power  pos- 
sessed by  the  flame  itself.  He  might  consider  how  that  from  one  flame 
another  can  be  kindled,  in  all  respects  like  its  parent  in  qualities  or 
shape ;  and  how,  in  succession,  from  one  original,  myriads  upon  myriads 
might  so  arise.  He  might  engage  himself  in  disquisitions  as  to  the  man- 
ner in  which  such  an  extraordinary  result  is  to  be  explained,  and  as  to 
the  source  to  which  he  should  impute  with  exactness  the  origin  of  each 
of  these  independent  flames,  and  their  mutual  interrelation.  He  might 
inquire  if  the  force  which  each  possesses  was  originally  contained  in  the 
original  flame,  and  how  it  came  to  give  it  forth  without  loss  of  any  of  its 
own  power.  He  might  also  amuse  himself  with  questions  of  individu- 
ality, and,  in  doing  all  this,  it  would  be  no  more  than  physiologists  have 
done  before.  Between  the  case  of  the  trees  and  flames,  of  which  we 
have  been  speaking,  it  is  not  difficult  to  see  that  there  is  an  analogy. 

Are  plants,  in  truth,  then,  nothing  more  than  temporary  states  through 
Plants  are  o  -  w^cn  material  substance  is  passing,  because  of  some  original 
erations,  not  physical  impression  made  upon  it,  and  the  present  operation 
als'  of  external  circumstances  ?  Can  individuality  be  applied  to 
them  any  more  than  to  a  flame  ?  Instead  of  being  individuals,  are  they 
not  rather  the  transitory  results  of  an  operation? 

The  lamp,  which  we  have  been  using  as  an  illustration,  may  serve  to 
Analo"- '  be  enlighten  our  path  a  little  farther.  In  the  infancy  of  chemis- 
tween  a  plant  try,  it  might  have  been  said  of  it  that  it  possessed  a  burning 
me'  power,  which  enabled  it  to  dispose  of  the  matter  with  which 
it  was  fed,  just  as  we  say  of  a  plant,  in  the  infancy  of  physiology,  that  it 
possesses  a  plastic  power,  which  groups  into  definite  forms  the  substance 
with  which  it  is  furnished.  The  so-called  burning  power  was  derived 
from  another  flame,  in  all  respects  analogous  to  that  which  manifests  it, 
and  is  nothing  more  than  an  extension  of  a  physical  operation,  the  tend- 
ency of  which,  so  far  from  being  to  check,  is  to  continue  as  iong  as  the 
proper  material  is  furnished.  The  lighting  of  a  second  flame  is  essen- 
tially the  same  condition  as  the  continued  combustion  in  the  first.  The 
fact  of  separateness  changes  the  phenomenon  in  no  respect  whatever ;  the 
relation  of  two  separate  flames  is  the  same  as  that  of  two  different  parts 
of  the  same  flame ;  and  so  the  derivation  of  a  plastic  power  by  a  plant 
from  its'  ancestor  is  essentially  the  same  thing  as  the  manifestation  of  a 
similar  power  in  different  parts  of  its  own  system. 

Though  it  may  therefore  be  convenient  to  speak  hypothetically  of  this 


NATURE  OF  THE  PLASTIC  POWER.  471 

principle  which  accomplishes  in  a  plant  the  grouping  of  its  parts  as  if  it 
were  an  agent,  the  foregoing  illustrations  show  us  that  all  the  facts  of  the 
case  are  equally  well  satisfied  on  the  supposition  that  it  is  the  continua- 
tion of  an  operation.  A  multitude  of  parallel  instances  present  them- 
selves. In  the  making  of  leavened  bread,  all  the  phenomena  would  seem 
to  be  accounted  for  either  upon  the  hypothesis  that  there  resides  in  the 
leaven  or  ferment  an  agent,  whose  quality  it  is  to  determine  a  specific 
change  in  the  flour,,  or  that  there  is  an  operation  which,  because  of  the 
chemical  conditions  existing,  is  gradually  spreading,  and  which  will  not 
cease  until  all  the  material  submitted  to  it  has  been  affected,  and  this  no 
matter  whether  it  be  in  the  same  mass  or  in  successive  portions.  Of 
such  hypotheses,  the  first  is  merely  an  elementary  idea,  the  latter  in- 
volves a  philosophical  conception. 

In  this  way,  therefore,  the  so-called  plastic  power  of  a  cell  or  the  germ 
of  a  seed  may  be  regarded  as  the  continued  manifestation  Nature  Of  the 
of  an  antecedent  impression  long  ago  made,  and  which,  un-  plastic  power. 
der  the  existing  conditions,  has  no  liability  to  wear  out  or  die  away; 
and  that  impression  may  have  been  purely  physical  in  its  nature. 

Viewed  in  this  attitude,  the  life  of  plants  is  a  physical  phenomenon. 
The  parts  of  which  they  are  composed  are  furnished  to  them  The  life  of 
by  influences  of  a  mechanical  kind :  their  carbon  is  taken  by  phans^ai  & 
a  true  chemical  decomposition  from  the  carbonic  acid  of  the  phenomenon. 
air ;  their  nitrogen  comes  from  ammonia  or  from  the  atmosphere.  Wa- 
ter is  drawn  by  capillary  attraction  from  the  ground.  In  virtue  of  its 
chemical  qualities,  it  carries  into  the  growing  system  the  various  saline 
bodies  present  in  the  soil,  and  which  are  needful  for  the  economy.  The 
sunlight,  heat,  rain,  winds,  are  the  supplying  and  nurturing  powers,  and 
the  grouping  agencies  residing  in  the  plant  are  of  the  same  mechanical 
derivation  or  order. 

The  germination  of  a  seed  and  the  growth  of  a  plant,  as  thus  consid- 
ered, show  us  to  what  an  extent  physical  forces  are  concerned  in  vege- 
table organization.  The  conclusion  thus  indicated  is  enforced  in  no 
common  manner  when  we  direct  our  attention  to  the  series  instead  of  to 
a  single  plant.  This  is  what  I  propose  to  do  in  the  following  chapter. 


472  GEOGRAPHY   OF   PLANTS. 


CHAPTER  II. 

ON  THE  INFLUENCE  OF  PHYSICAL  AGENTS  ON  THE  ORGANIC  SERIES. 

Of  the  Geography  of  Plants:  their  horizontal  and  vertical  Localization. — Influence  of  Heat  on  or- 
ganic Distribution :  isotheral  and  isochimenal  Conditions. — Effects  of  Variations  in  the  Dens- 
ity of  the  Air,  Moisture,  Soil,  Sunlight,  Length  of  Day. — Definite  Quantity  of  Heat  required 
by  Plants. 

Secular  Perturbations  in  the  Species  of  Plants. — Long  Periods  of  Time  required. — Secular  geo- 
logical Changes. 

Inverse  Problem  of  the  Investigation  of  the  Earth's  History  from  her  fossil  Flora. —  Two  great 
terrestrial  Epochs :  Change  in  the  Constitution  of  the  Air,  and  Localization  of  Organisms 
through  Decline  of  the  Earth's  Interior  Heat. 

Difference  between  abrupt  and  gradual  Impressions. — Invariable  Causes  may  produce  abrupt 
Crises.  , 

Extension  of  the  above  Principles  to  the  Case  of  Animals. —  Case  of  the  Inca  Indians. 

General  Argument  supported  by  the  Extinction  of  Forms. — Development  is  under  the  Influence  of 
Law. — Rudimentary  Organs  and  Excesses  of  Development. — The  Idea  of  Development  by 
Law  consistent  with  natural  Facts. 

THE  publication  of  HUMBOLDT'S  Essay  on  the  Geography  of  Plants 
Geo  ra  hical  ^rst  f°rma^y  drew  the  attention  of  botanists  to  the  connec- 
distribution  of  tion  between  the  distribution  of  vegetables  and  the  distribu- 
tion of  heat  on  the  surface  of  the  globe.  Starting  from  the 
equator  and  advancing  to  the  pole,  in  either  hemisphere,  the  mean  annual 
temperature  declines  as  the  latitude  becomes  greater,  and  in  succession  a 
series  of  vegetable  zones,  merging  gradually  into  each  other,  though  each, 
where  best  marked,  perfectly  distinguished  from  the  succeeding,  is  encoun- 
tered. In  the  tropics  we  have  the  palms,  which  give  so  striking  a  charac- 
teristic to  the  forests,  the  broad-leaved  bananas,  and  the  great  climbing 
plants,  which  throw  themselves  from  stem  to  stem  like  the  rigging  of  a 
ship.  Next  follows  a  zone  described  as  that  of  evergreen  woods,  in  which 
the  orange  and  the  citron  come  to  perfection.  Beyond  this,  another  of 
deciduous  trees — the  oak,  the  chestnut,  and  the  fruit-trees  with  which, 
in  this  climate,  we  are  so  well  acquainted,  and  here  the  great  climbers  of 
the  tropics  are  replaced  by  the  hop  and  the  ivy.  Still  farther  advanc- 
ing, we  pass  through  a  belt  of  conifers — firs,  larches,  pines,  and  other 
needle-leaved  trees,  and  these,  leading  through  a  range  of  birches,  which 
become  more  and  more  stunted,  introduce  us  to  a  region  of  mosses  and 
saxifrages,  but  which  at  length  has  no  tree  nor  shrub ;  and  finally,  as 
the  perpetual  polar  ices  are  reached,  the  red  snow-alga  is  the  last  trace 
of  vegetable  organization. 

A  similar  series  of  facts  had  been  observed  by  Tournefort  in  an  ascent 


GEOGEAPHY  OF  PLANTS.  473 

of  Mount  Ararat.  He  found  that  the  distribution  of  the  veg-  yertical  dis_ 
etation  from  the  base  to  the  top  of  the  mountain  bore  a  gen-  tribution  of 
eral  resemblance  to  the  distribution  from  the  base  toward  the  p  a 
Arctic  regions.  These  facts  by  subsequent  observers  were  generalized, 
it  having  been  established  that  there  exists  an  analogy  between  horizon- 
tal distribution  on  the  surface  of  the  globe  and  vertical  distribution  at 
different  altitudes  above  the  level  of  the  sea.  Even  in  the  tropics,  if  a 
mountain  be  sufficiently  high,  a  very  short  ascent  suffices  to  carry  us 
from  the  characteristic  endogenous  growths  at  its  foot,  in  succession, 
through  a  zone  of  evergreens  into  one  of  deciduous1  trees,  and  this,  again, 
into  one  of  conifers,  the  vegetation  declining  through  mosses  and  lichens 
as  we  reach  the  region  of  perpetual  snow. 

In  these  two  cases  of  horizontal  and  vertical  distribution  respectively, 
which  thus  present  such  a  striking  botanical  resemblance,  Distribution 
there  is  likewise  so  clear  a  meteorological  analogy  that  it  is  ofheatdeterm- 

0      ,      .          ,  ,  ines  the  distri- 

impossible  to  avoid  coming  to  the  conclusion  that  the  dis-  button  of 
tribution  of  plants  depends  on  the  distribution  of  heat.  The  Plants- 
same  climate  variation  encountered  on  a  surface  journey  directed  from 
the  equator  toward  the  poles  is  again  encountered  as  we  leave  the  foot 
of  a  tropical  mountain  and  go  toward  its  summit ;  for  it  is  a  well-ascer- 
tained fact  that  the  temperature  of  the  atmosphere  declines  as  we  rise  to 
greater  altitudes,  and  that,  no  matter  how  high  the  summer  heat  may  be, 
we  may,  by  a  vertical -ascent  at  any  locality,  come  to  a  region  where 
the  temperature  is  never  above  32°  Fahr.,  and  where  ice  and  snow,  there- 
fore, never  melt.  If,  in  any  locality,  the  mountain  ranges  are  of  sufficient 
height  to  gain  that  region,  their  tops  will  be  covered  with  perpetual 
snow.  The  vertical  ascent  thus  to  be  made  is  less  as  the  latitude  is 
greater.  At  the  equator  it  is  15,200  feet,  and  at  the  eightieth  degree  it 
is  within  450  feet  of  the  ground.  Beyond  this,  the  surface  itself  is  per- 
petually frozen. 

The  mean  temperature  of  a  place  determines  its  vegetable  growth,  and 
hence  there  will  ever  be  a  resemblance  between  the  vegetation  of  places 
of  the  same  mean  temperature,  though  they  may  be  geographically  very 
wide  apart.  But  this,  though  a  resemblance,  is  very  far  from  being  an 
identity.  We  can  not  always  designate  by  name  the  particular  plants  of 
a  high  latitude  which  should  be  found  at  a  corresponding  elevation  in  the 
mountains  of  the  tropics.  There  may  be  the  general  resemblance  of 
which  we  have  been  speaking,  and  yet  the  genera  and  species  of  plants 
in  the  two  places  may  be  quite  distinct.  But  this  fact,  far  from  affecting 
the  truth  to  which  we  have  arrived  of  the  control  of  a  physical  agent 
such  as  heat  over  the  distribution  of  plants,  leads  us  to  ex-  Influence  of 
tend  it,  and  teaches  us  that,  though  we  might  expect,  in  other  physical 
places  far  apart,  identically  the  same  vegetable  growths  if  conditions- 


474  INFLUENCE   OF   PHYSICAL  CONDITIONS. 

all  the  physical  conditions  were  identical,  yet,  since  heat  is  only  one  of 
these  conditions,  it  alone  is  insufficient,  and  that  differences  in  the  press- 
ure of  the  air,  the  amount  of  moisture,  the  quantity  of  carbonic  acid,  as 
also  variations  in  the  constitution  of  the  soil,  must  have  their  effect.  In- 
stead, then,  of  limiting  our  views  to  the  control  of  temperature  over  the 
occurrence  of  plants,  we  must  enlarge  them  in  such  a  way  as  to  include 
divers  other  influences,  some  of  which  are  those  just  mentioned,  and  all 
are  equally  of  a  physical  kind. 

This  therefore  brings  before  us,  in  an  impressive  manner,  the  subject  to 
which  this  chapter  is  devoted,  the  influence  of  physical  agents  generally 
over  organization. 

That  the  conditions  of  temperature  alone  are  insufficient  to  account  for 
the  occurrence  and  distribution  of  plants  may  be  clearly  established  by 
the  aid  of  another  series  of  facts.  Throughout  the  old  continent,  with 
the  exception  of  its  torrid  zone,  from  the  south  of  Africa  to  the  north  of 
Europe,  heaths  abound,  their  species  being  very  numerous  in  the  south- 
ern latitudes,  less  so  in  the  northern,  but  the  individuals  increasing  in 
number  as  the  species  diminish.  At  the  extreme  north  the  common 
heather  remains  as  the  sole  representative  of  the  whole  group,  and  so 
universally  covers  the  surface  as  to  give  a  characteristic  feature  to  the 
landscape.  But  in  America,  which  reaches  through  all  corresponding 
degrees  of  latitude,  and  has  in  its  proper  localities  the  same  mean  tem- 
peratures, not  a  single  heath  ever  occurs.  Again,  in  the  New  World, 
through  forty  degrees  on  each  side  of  the  equator,  the  cactus  tribe  of  all 
kinds  of  grotesque  forms  abounds,  but  in  Africa,  though  there  are  local- 
ities of  corresponding  temperature,  not  a  single  cactus  is  to  be  seen.  The 
spurges  there  make  their  appearance.  So,  again,  in  Australia,  the  forests 
present  a  melancholy  and  shadeless  character  from  their  leafless  casuari4- 
nas,  acacias,  and  eucalypti,  whereas,  if  temperature  alone  were  concern- 
ed, they  should  offer  the  same  aspect  as  the  forests  of  North  America 
and  Europe. 

Restricting  our  examination  for  the  present  to  the  influence  of  heat,  it 
Influence  of  may  be  observed  that  this  is  by  no  means  so  simple  as  might 
h^atTand  win-  at  ^rst  aPPear-  I*s  distribution  does  not  correspond  with 
ter  colds.  the  latitude,  the  lines  of  equal  mean  temperature,  isothermal 
lines,  not  coinciding  with  the  parallels  of  latitude.  If  we  examine  the 
zones  of  plant  distribution  just  described,  we  find  that  they  follow  the 
isothermal  lines  much  more  closely  than  the  latitudes ;  but  even  here, 
again,  there  are  very  great  deviations — deviations  which,  however,  are  to 
some  extent  understood  when  we  recall  that  it  is  not  so  much  with  the 
mean  annual  temperature  that  plants  are  concerned  as  with  the  special 
temperature  of  particular  moments  of  the  year.  For  the  most  part  they 
are  affected  by  the  heat  of  the  summer  season,  which  is  their  period  of 


INFLUENCE   OF  THE  AIR  AND  MOISTUKE.  475 

growth,  and  though  two  localities  may  have  the  same  mean  annual  tem- 
perature, it  does  not  follow  that  their  maximum  of  cold  for  the  winter, 
and  their  maximum  of  heat  for  the  summer,  should  coincide.  It  was 
such  considerations  that  led  to  the  construction  of  isotheral  lines,  or  those 
of  equal  summer  heat,  and  isochimenal  lines,  or  those  of  equal  winter 
cold. 

Into  the  causes  which  bring  about  this  difference  of  heat  distribution 
it  is  not  necessary  for  us  here  to  inquire  minutely.     They  Causes  of  the 


are  very  various.     The  prevalent  winds  at  different  seasons  S" 


of  the  year,  ocean  currents,  the  geological  structure  of  a  coun-  heat. 
try,  even  what  might  be  termed  its  optical  qualities,  that  is,  its  power  of 
absorbing  the  rays  of  the  sun  (for  instance,  the  great  Desert  of  Sahara 
disturbs  the  temperature  of  all  Europe),  and  upon  like  principles  must 
act  the  removal  of  extensive  forests,  and  their  substitution  by  equivalent 
surfaces  of  cultivated,  differently  colored,  and  differently  absorbing  lands, 
elevation  above  the  sea  level,  for  the  higher  the  country  the  lower  its 
temperature  :  these,  and  a  multitude  of  other  such  conditions,  impress 
an  effect  upon  the  distribution  of  heat.  The  mean  annual  temperature 
represents  these  and  all  other  such  influences,  and  includes  all  the  varia- 
tions, diurnal  and  nocturnal,  monthly  and  seasonal,  for  the  year. 

The  organic  functions  of  a  plant  demand  particular  temperatures  at 
particular  times.  There  is,  doubtless,^  special  degree  best  suited  to  the 
period  of  germination,  another  to  the  period  of  aerial  growth,  another  to 
the  period  of  fertilization,  and  another  to  that  of  ripening  the  seeds  ;  and 
these  degrees  differ  in  the  case  of  different  plants.  Where  the  require- 
ments become  so  complicated,  it  would  be  erroneous  to  expect  that  the 
mean  annual  temperature  should  satisfy  them  all. 

Connected  in  part  with  temperature,  and  in  part  with  elevation  above 
the  sea,  are  the  variations  in  the  density  of  the  air.  These  influence  of  va- 
control,  to  a  certain  extent,  the  aerial  supply  to  plants,  the  riations  in  the 

.  i  .  .  ,       T  density  of  the 

quantity  presented  to  their  leaves  diminishing  as  the  density  air—  moisture, 
becomes  less.  etc' 

The  same  observation  may  be  made  respecting  moisture,  which,  as  is 
very  well  known,  constitutes  one  of  the  most  influential  conditions  in  de- 
termining the  growth  of  plants,  and  this  in  a  double  way,  either  as  va- 
por contained  in  the  air  or  as  rain.  The  effect  of  rain  in  this  respect  is 
twofold  :  it  diminishes  the  quantity  of  atmospheric  carbonic  acid  by 
exerting  over  it  a  solvent  power,  carrying  it  into  the  ground,  and  thereby 
reducing,  by  sometimes  as  much  as  one  half,  the  supply  on  which  the 
leaves  are  depending  ;  it  also  brings  in  larger  quantities  to  the  interior 
of  the  plant  the  saline  constituents  of  the  soil  which  are  requisite  for  tis- 
sue development. 

To  variations  in  the  temperature,  the  density  of  the  air,  and  its  moist- 


476  INFLUENCE   OF  THE  SOIL  AND   LIGHT.     . 

Influence  of  ure,  as  affecting  the  well-being  of  plants,  may  be  added  the 
the  soil.  chemical  constitution  of  the  soil  upon  which  they  grow.  Lime- 
plants  can  never  be  developed  except  on  soils  in  which  that  earth  abund- 
antly occurs,  and  the  same  may  be  said  of  potash  or  soda  plants,  or,  in 
short,  of  any  which  demand  some  special  mineral  ingredient.  Thus,  for 
instance,  the  salsolas  and  salicornias,  which  grow  abundantly  on  the  At- 
lantic shores  of  France,  and  which  require  for  their  development  the 
saline  ingredients  of  the  sea,  are  nowhere  to  be  seen  throughout  Central 
Europe,  though  they  reappear  on  the  salt  steppes  of  Russia,  and  abound 
around  the  Caspian.  We  should  scarcely  expect  that  sea-weeds,  into 
the  composition  of  which  bromine  and  iodine  abundantly  enter,  should 
ever  grow  in  waters  from  which  these  chemical  elements  are  totally  ab- 
sent. Upon  these  principles,  the  vegetation  of  extensive  tracts  of  coun- 
try has  undergone  a  change  in  an  artificial  way.  Thus,  for  instance,  in 
Virginia  and  other  Southern  States,  we  may  pass  for  miles  in  succession 
through  tracts  in  which  the  ancient  forest-growths  have  been  replaced 
by  the  Pinus  teeda,  or  old  field  pine.  These  are  tracts  from  which  the 
potash  salts  have  been  removed,  to  a  great  extent,  by  the  culture  of  to- 
bacco. And  of  the  indigenous  trees,  this  pine  requires  the  smallest  pro- 
portion of  those  salts.  It  therefore  can  flourish  where  -the  others  can 
not  exist. 

From  what  has  been  said  in  tjie  last  chapter,  it  may  be  inferred  that 
Influence  of  among  the  various  conditions  thus  influencing  the  growth  of 
the  sun's  light.  a  plant,  none  are  of  greater  importance  than  the  amount  of 
light  furnished  to  it.  Through  this  agent  the  decomposition  of  carbonic 
acid  is  effected,  and  the  plant  obtains  from  the  air  the  carbon  it  requires, 
out  of  which  its  solid  structures  are  for  the  most  part  built.  The  rapid- 
ity with  which  the  reduction  of  the  carbonic  acid  takes  place  depends 
upon  the  brilliancy  of  the  light,  and  the  amount  of  carbon  thus  obtained 
upon  that  condition  and  the  time  of  exposure  conjointly.  The  amount  of 
light  received  from  the  sun  in  any  locality  depends  in  a  general  way,  as 
does  the  heat,  upon  the  latitude ;  but  in  both  cases  a  multitude  of  disturb- 
ing agencies  intervene.  Variations  of  moisture  control  the  supply  of  light 
by  permitting  a  translucency,  or  establishing  its  opposite,  a  cloudiness  or 
murkiness  of  the  air.  Other  meteorological  causes,  as,  for  example,  winds, 
by  condensing  or  removing  moisture,  act  in  like  manner ;  so  also  do  as- 
influence  of  tronomical  conditions,  especially  by  influencing  the  relative 
the  position  of  length  of  the  day  and  night ;  for,  as  we  advance  toward  the 

the  sun  and  ,fo     .  J  .     b_  .      .       .          _  ,  . 

length  of  the  pole,  the  summer  sun  is  above  the  horizon  longer  and  longer. 
day-  In  Northern  Europe,  during  the  month  of  June,  he  never  sets, 

but  remains  all  night,  if  night  it  can  be  called,  above  the  horizon ;  and, 
as  Berzelius  well  remarks,  "Under  the  influence  of  this  midnight  sun  of 
the  North,  the  life  of  plants  runs  through  the  same  cycle  of  change  in 


DEFINITE   QUANTITY   OF   HEAT   REQUIRED.  477 

six  weeks  which  it  takes  four  or  five  months  to  accomplish  in  beautiful 
Italy." 

Attempts  have  been  made  to  establish  the  doctrine  that  every  plant 
requires,  from  the  time  of  its  germination  to  the  close  of  its  Definite  quan- 
organic  activity,  a  definite  amount  of  heat.  The  following  qufred  by^ ' 
example,  in  the  case  of  barley,  is  furnished  by  Schleiden.  plants. 
"  In  Egypt,  on  the  banks  of  the  Nile,  barley  is  sown  at  the  end  of  No- 
vember, and  harvested  at  the  end  of  February ;  the  period  of  vegetation, 
therefore,  amounts  to  about  90  days,  and  the  meail  temperature  of  this 
season  is  69°  48'.  ,In  Tuqueres,  near  to  Cumbal,  under  the  equator,  the 
time  of  sowing  in  the  mountains  for  barley  is  about  the  1st  of  June,  the 
time  of  harvest  the  middle  of  November ;  the  mean  temperature  of  this 
vegetating  season  of  168  days  is  50°  12'.  At  Santa  Fe  de  Bogota  they 
number  122  days  between  seed-time  and  harvest,  with  a  mean  tempera- 
ture of  57°  24'.  If,  now,  the  number  of  days  is  multiplied  by  the  figures 
of  the  mean  temperature,  we  obtain  6282  for  Egypt,  8433-|^  for  Tuque- 
res,  for  Santa  Fe  6489-|-J ;  therefore  as  nearly  the  same  number  as  the 
uncertainty  in  the  estimate  of  the  days,  the  accurate  mean  temperature, 
and  the  want  of  knowledge  whether  or  not  the  same  kind  of  barley  is 
cultivated  in  all  the  places,  will  allow  us  to  expect.  Similar  results  are 
obtained  for  wheat,  maize,  the  potato,  and  other  cultivated  plants.  We 
may  express  these  results  thus :  Every  cultivated  plant  requires  a  cer- 
tain quantity  of  heat  for  its  development,  but  it  is  the  same  thing  wheth- 
er this  heat  is  distributed  over  a  shorter  or  longer  space  of  time,  so  that 
certain  limits  are  not  exceeded ;  for  where  the  mean  temperature  sinks  be- 
low 36°  24',  or  where  it  rises  above  71°  36',  barley  will  no  longer  ripen. 
Consequently,  to  define  accurately  the  conditions  of  temperature  which  a 
plant  requires  to  maintain  it  in  a  flourishing  condition,  we  must  state 
within  what  limits  its  period  of  vegetation  may  vary,  and  what  quantity 
of  heat  it  requires.  This  most  remarkable  circumstance  was  first  ob- 
served by  Boussingault,  but,  unfortunately,  we  as  yet  possess  not  nearly 
sufficiently  accurate  accounts  of  the  conditions  of  culture  in  the  various 
regions  of  the  earth  to  enable  us  to  follow  out  this  ingenious  view  in  all 
its  details." 

Respecting  the  calculations  offered  in  the  preceding  paragraph,  the  re- 
mark may  be  made  that  they  contain  an  element  which  vi-  xhe  effect  of 
tiates  their  correctness,  and  that,  if  the  proper  data  were  re-  the  intensity 

,  ,  ,        .      .   ,      .  -i    -i         T        -i  -i   an(i  quantity 

sorted  to,  the  general  principle  intended  to  be  demonstrated  Of  heat  consid- 
would  be  far  more  clearly  established.  The  degrees  of  the  ered- 
thermometer  are  not  the  data  required,  for  that  instrument  indicates  the 
intensity,  but  not  the  quantity  of  heat.  If  some  form  of  calorimeter  were 
substituted  for  it,  the  result  would  turn  out  very  differently.  As  an  illus- 
tration, if  a  mass  of  ice  of  constant  surface  was  exposed  to  the  warmth  in 


478  GENERATION   OF   HEAT. 

each  of  these  various  cases,  the  quantity  of  water  arising  from  its  melt- 
ing should  be  the  same  at  the  close  of  the  specified  number  of  days.  In 
this  case  the  true  element  is  introduced — the  element  of  quantity,  as  de-' 
termined  by  one  of  the  ordinary  calorimetric  methods. 

It  is  not,  however,  to  be  inferred  from  this  criticism  that  the  peculiar 
quality  of  heat  which  we  recognize  indifferently  by  the  terms  intensity, 
temperature,  or  degree,  is  without  significance  in  the  case  of  plants  :  the 
limiting  maxima  and  minima  between  which  a  given  plant  can  exist 
prove  that  both  conditions  exert  an  influence,  though  they  exert  it  in  a 
different  way.  Doubtless  a  plant,  from  the  time  of  its  germination  to 
that  of  the  completion  of  its  organic  life,  must  have  a  definite  quantity 
of  heat  measured  out  to  it,  but  its  organic  functions  might  be  fatally  in- 
terfered with  if  the  temperature  should  rise  above  a  limiting  maximum, 
or  sink  beneath  a  minimum. 

The  definite  quantity  of  heat  in  this  manner  demanded  by  each  plant 
is  probably  connected  with  a  purely  mechanical  effect — the  necessity  for 
the  evaporation  of  a  definite  quantity  of  water  by  the  leaves.  The  inor- 
ganic salt  substances  required  by  every  plant  are  introduced  through  its 
roots  in  a  state  of  solution  in  water,  and,  since  these  salts  are  mostly  of 
sparing  solubility,  a  great  quantity  of  water  is  required  to  accomplish 
the  object.  Nevertheless,  they  are  dissolved  at  a  given  heat-degree  in 
an  invariable  proportion  in  the  liquid,  and  are  required  by  the  plant  in  a 
determinate  proportion  as  compared  with  its  mass ;  so  that,  were  there 
no  other  reason,  this  doubtless  would  be  sufficient  to  account  for  the  cir-x 
cumstance  under  consideration. 

It  should  also  be  remembered  that  every  plant  generates  a  certain 
Disturbance  amount  of  heat,  which  varies  with  its  organic  condition  at  the 
arising  from  time.  The  experiments  of  Professor  Paine  present  this  in  an 
tion  ofheat  interesting  point  of  view.  The  following  extract  is  from  the 
in  plants.  Medical  and  Physiological  Commentaries,  vol.  ii.,  p.  75 : 

"On  the  9th  of  April,  1839,  we  repaired  to  a  forest  in  New  Jersey, 
Prof.  Paine's  provided  with  very  delicate  thermometers,  of  Fahrenheit's 
experiments.  scale)  constructed  for  our  object.  The  bulbs  were  no  larger 
than  the  stem,  the  range  of  the  mercury  extensive,  and  the  degrees 
marked  upon  the  glass.  The  stems  filled  exactly  the  bore  of  a  small 
spiral  auger,  and  when  the  glass  was  introduced  the  air  was  excluded  by 
applying  a  silk  handkerchief  around  the  hole.  The  perforations  were  all 
made  on  the  northern  side  of  the  trees.  Fifteen  minutes,  at  least,  were 
allowed  for  the  subsidence  of  the  heat  that  arose  from  the  friction  of  the 
perforator,  and  the  thermometer  was  generally  reapplied  at  different  in- 
tervals afterward.  The  perforations  were  made  about  four  feet  above  the 
ground,  and  the  diameters  of  the  trees  were  ascertained  at  this  point. 
When  the  diameter  was  five  inches  or  more,  the  perforations  were  made 


VARIATIONS   IN   THE  SPECIES. 


479 


to  the  depth  of  two  and  a  half  inches.  When  the  diameter  was  less  than 
five  inches,  the  thermometer  was  introduced  as  far  as  the  centre  of  the 
tree." 

Of  the  tables  given  by  Professor  Paine  I  select  the  following : 
"  Range  of  thermometer  in  the  shade  during  the  observations,  which 
lasted  six  hours,  from  38°  to  52°  :  near  freezing  at  sunrise. 

"A  dead  upright  dry  tree  was  selected  as  a  standard  of  comparison. 
Its  diameter  was  twelve  inches.  The  temperature  of  this  tree,  at  the 
close  of  our  observations,  was  45°  at  the  centre  and  in  all  other  parts. 


"  Juglans  squamosa,       diameter  10    inches,  48°  Buds  slightly  enlarging, 
do.            d6.                   '6        "        49°                   do. 

Fagus  sylvatica, 
Quercus  tinctoria,           A 
Castanea  Americana, 
Betula  nigra, 
Salix  Babylonica, 
do.         do. 

'        10        " 

t          7        u 

«         12        " 
.          4        " 
18        " 

«        18        " 

49°  Buds  swelling. 
49°  No  budding. 
50°          do. 
51°  Elowering. 
53°  Buds  unfolded. 
53°            do. 

Pinus  Canadensis, 
Platanus  Occidentalis, 
do.             do. 

'         18        " 
<         18        " 
*;:        6        " 

54° 
50°  No  budding. 
54°         do. 

do.             do. 

<           4         '• 

55°         do. 

Juniperus  Viginiana, 
Kobinia  pseudacacia, 
Populus  Ia3vigata, 
do.          do. 

«  :_      4        » 
«          B       " 
4       " 
4        " 

55° 
62°         do. 
62°  In  bloom. 
64°        do. 

do.         do. 

«          3        " 

63°        do. 

do.         do.                   "          3       " 

65°        do. 

do.          do.                   "          2 

67°        do. 

do.         do.                   «          1|      " 

68°        do." 

The  'heat  which  is  thus  liberated  by  plants  stands  in  the  stead  of  a 
certain  amount  of  atmospheric  heat,  and  therefore  complicates  the  preced- 
ing considerations. 

By  such  facts  as  those  which  have  now  been  presented,  we  may  be 
satisfied  that  the  well-being  of  plants  is  affected,  and  even  Accomplish-  • 
their  existence  determined  by  the  influence  of  external  agents,  "onsinthe  sp&. 
and  that,  in  this  manner,  they  are  capable  of  having  changes  cies  of  plants, 
impressed  upon  them  even  in  an  artificial  way.  If  we  furnish  to  them 
those  materials  or  conditions  which  their  circumstances  require,  they  will 
grow  with  luxuriance,  or  under  an  opposite  state  of  things  will  dwarf 
away ;  and  where,  for  a  long  period  of  time,  such  conditions  are  imposed 
upon  successive  generations  of  them,  a  permanent  change  may  be  effect- 
ed, those  which  have  appeared  as  varieties  assuming  the  more  definite 
form  and  persistency  of  sub-species.  The  general  impression  alluded  to 
in  the  last  chapter,  that  such  peculiarities  are  only  to  be  extended  by 
budding  or  other  equivalent  operations,  and  that  those  which  we  regard 
as  different  individuals  are  truly  fragments  or  parts  of  the  same  individ- 
ual, does  not  here  properly  apply.  A  like  propagation  of  peculiarity  is, 


480  SECULAR   CHANGES  IN  PLANTS. 

in  a  multitude  of  instances,  accomplished  by  the  use  of  seeds,  and  this 
precisely  in  the  instance  in  which  we  should  be  led  to  expect  it.  Of 
our  kitchen-garden  plants,  the  carrot,  the  beet,  the  turnip,  the  cabbage,  the 
pea,  etc.,  we  propagate  the  expected  kind  without  any  uncertainty  by  the 
use  of  seeds,  never  supposing  that  they  will  run  back  to  the  wild  stock, 
or  give  origin  to  plants  different  to  those  from  which  they  were  derived. 
The  care  of  man,  exerted  for  many  years  upon  these  vegetables,  has,  then, 
impressed  upon  them  a  change  very  far  from  ephemeral  in  its  nature,  and 
enabled  them  to  pass  from  the  condition  of  mere  varieties  into  that  of 
actual  sub-species. 

Acknowledging,  therefore,  the  influence  which  physical  agents  exert  on 
Necessity  of  the  growth  and  development  of  plants,  and  admitting  that 
time  forchan^  favormg  circumstances  will  bring  on  a  modification  of  form, 
ing  plants.  especially  if  applied  long  enough,  and  that  man  himself,  by 
his  arts  of  culture,  can,  without  difficulty,  establish  similar  variations,  we 
might  be  led  to  expect  that  more  profound  changes  in  external  circum- 
stances, if  steadily  applied  through  extended  periods  of  time,  would  give 
origin  to  more  striking  results.  A  variation  in  the  constitution  of  the  air, 
in  the  brilliancy  of  light,  in  the  mean  temperature,  moisture,  or  chemical 
constitution  of  the  soil,  if  kept  up  for  thousands  of  years,  or  permanent- 
ly established,  could  not  fail  to  exert  a  prodigious  effect  upon  the  whole 
vegetable  world.  If,  for  example,  the  brilliancy  of  the  sun  in  the  slow 
lapse  of  centuries  should  gradually  decline,  or  the  mean  temperature  of 
the  surface  of  the  earth  should  descend,  or  enormous  quantities  of  car- 
bonic acid  be  permanently  removed  from  the  air  and  replaced  by  equiva- 
lent volumes  of  oxygen  gas  ;  if  carbonate  of  lime,  to  an  extent  sufficient 
for  the  formation  of  geological  strata,  were  removed  from  the  waters,  in 
which  it  could  no  longer  be  held  in  solution  because  of  the  withdrawal 
of  carbonio  acid  from  the  atmosphere,  it  must  follow,  as  a  matter  of  inev- 
itable necessity,  that  the  whole  vegetable  world  would  feel  the  change. 
Plants  that  at  one  time  existed  could  exist  no  more  ;  others,  by  gradu- 
ally accommodating  themselves  to  the  slow  revolution,  would  exhibit 
here  the  development  of  one  part,  there  the  development  of  another,  and 
some,  which  perhaps  maintain  themselves  with  difficulty  under  the  old 
state  of  things,  would  now  begin  to  develop  themselves  in  a  more  luxu- 
riant way. 

The  changes  here  spoken  of  hypothetically  have,  however,  actually  oc- 
Secuiar  changes  cur*ed  in  the  history  of  the  earth.  We  can  not  shut  our 
occurring  to  the  eyes  to  the  corresponding!;  march  which  vegetation  has  made, 

earth  and  occa-     J  .      .*  ,?  i      •     i  A-  vo_  ^.i. 

commencing  in  the  earliest  geological  times  with  the  stem- 


turns  in  plants.  iess  cryptogamia,  followed  by  those  provided  with  stems 
and  leaves,  the  gymnospores,  such  as  the  conifers  and  cycadeas,  next 
making  their  appearance,  after  these,  monocotyledons,  and  at  last  the 


EPOCHS  OF  THE  GLOBE.  481 

dicotyledons — a  steady  progression  from  those  which  we  may  term  of  a 
lower  to  those  of  a  more  elevated  organization,  and  all  this  was  produced 
Iby  the  influence  of  physical  agents. 

On  so  firm  a  footing  may  we  regard  this  doctrine  as  now  placed,  that 
we  can  use  it  for  the  purpose  of  determining  from  the  ascer-  .  ,.  .. 
tained  botanical  condition  of  our  planet  at  any  period  the  these  principles 
physical  conditions  under  which  she  then  existed,  and  this  inverse1^- 
with  a  precision  constantly  becoming  greater.  Among  the  more  impor- 
tant facts  which  have  been  distinctly  made  out,  a  few  may  be  cited  as 
illustrations  of  the  subject  now  treated  of.  For  example,  1st.  The  ex- 
istence of  a  tropical  climate  in  regions  of  very  high  latitude,  as  is  proved 
by  the  occurrence  of  fossil  tropical  plants  therein ;  2d.  That  all  over  the 
globe  the  temperature  was  once  nearly  uniform,  nothing  answering  to 
what  we  now  term  climates  existing,  as  is  proved  by  the  uniformity  of 
the  vegetable  growths  preserved  as  coal  from  the  equator  to  near  the  polar 
circles — great  arborescent  cryptogamia,  exceeding  in  size  the  arborescent 
ferns  now  growing  in  the  Pacific  islands  under  the  equinoctial  line. 
From  such  a  botanical  fact,  we  reason  without  error  to  the  Succession  of 
conclusion  that  in  those  times  the  influence  of  the  sun,  so  climates  on  the 
far  as  the  supply  of  heat  was  concerned,  must  have  been  ined  from  its 
wholly  overpowered,  the  intrinsic  temperature  of  the  planet  fossil  flora- 
obliterating  all  climate  subdivisions.  3d.  That  these  climate  subdivis- 
ions, which  are  now  presented  as  existing  side  by  side  in  zones  upon  the 
planet,  were  introduced  for  each  latitude  in  an  order  of  succession  as  to 
time ;  that  even  the  frigid  zone,  by  reason  of  the  cooling  of  the  earth, 
has  passed  through  an  ultra-tropical,  a  tropical,  and  a  temperate  degree 
of  heat  to  reach  its  present  state ;  4th.  That  the  extinction  of  the  old 
vegetable  forms  was  accomplished  by  an  inability  of  those  organisms  to 
maintain  themselves  in  the  physical  revolution  that  was  gradually  taking 
place.  Among  such  may  be  mentioned  the  dying  out  of  gigantic  equi- 
setums  or  horsetails  twenty  feet  high,  club  mosses  rivaling  forest  trees, 
calamites  and  stigmarias,  these,  as  they  disappeared,  being  replaced  by 
cycadacese,  and  coniferge,  and  tree-like  liliacese.  Even  long  after  the  de- 
posit of  the  coal  there  flourished  in  England  innumerable  palms,  which 
maintained  themselves,  with  their  tropical  associates,  into  the  tertiary 
times. 

Among  the  physical  events  which  geological  researches  disclose,  there 
are  two  of  surpassing  importance  in  the  history  of  the  globe,  Two  epochs  in 
and  both  of  them  immediately  connected  with  the  doctrine  the  history  of 
we  have  under  discussion ;  these  are  the  change  impressed  *  e  g  ° 
on  the  atmosphere  by  the  withdrawal  from  it  of  those  enormous  masses 
of  carbon  deposited  under  the  different  forms  of  coal,  and  the  localiza- 
tion of  plants  and  animals  in  climate  distribution  as  the  sun's  rays  be- 

HH 


482  LOCALIZATION   OF  PLANTS. 

gan  to  assert  their  influence  through  the  lowering  of  the  surface  temper- 
Change  in  the  ature  of  the  globe.  The  first  of  these  events  was  not  alone 
tbTa7mos°n  °f  liimted in  its  effect  to  a  Disturbance  of  the  organic  functions 
phere.  of  plants  by  diminishing  the  amount  of  gaseous  material  from 

which  they  gathered  their  support  in  the  air :  its  influence  was  also  felt 
in  animal  life  by  rendering  that  possible  which  was  not  possible  before 
— the  existence  of  the  quickly-respiring  and  hot-blooded  tribes ;  for  it  fol- 
lows as  a  chemical  necessity  that,  under  the  circumstances  of  the  case, 
the  removal  of  the  carbonic  acid  was  attended  with  the  evolution  of  an 
equal  volume  of  oxygen  gas.  As  respects  the  influence  of  the  sun,  which 
gradually  led  to  the  establishment  of  climates,  first  in  an  order  of  time, 
and  then  in  an  order  of  place,  this  was  the  signal  for  the  localization  of 
Definite  locaii-  P^ants  an(l  animals  i*1  definite  regions.  From  many  coun- 
zation  of  plants  tries  which  they  had  thus  far  inhabited  they  were  now  ex- 
and  animals,  p^^  an(j  "barriers  of  temperature  placed  around  them  which 
they  could  never  again  overpass.  And  as  these  great  changes  occurred, 
they  were  attended  by  the  extinction  of  countless  forms  in  both  king- 
doms, which  were  utterly  unable  to  maintain  themselves  in  the  new  cir- 
cumstances around  them,  their  places  being  occupied  by  the  extension 
of  contemporaneous  forms,  or  by  the  appearance  of  others  that  were  whol- 
ly new. 

As  an  illustration  of  the  manner  in  which  a  vegetable  organism  may 

Exam  le  of  the  ^e  use(^  *n  ^^s  inverse  Wa7  f°r  tne  determination  of  physic- 
inverse  method  al  conditions,  I  may  introduce  the  following  quotation  from 
len*  Schleiden :  "  The  gradual  conversion  of  the  universal  trop- 
ical climate  into  the  present  climatal  zones  may  be  shown  in  another 
very  interesting  manner  in  quite  a  special  instance.  All  ligneous  trunks 
of  coniferous  trees  continually  increase  in  thickness  at  all  parts  of  their 
circumference.  In  the  equatorial  regions,  where  the  climate  retains  the 
same  character  uninterruptedly  throughout  the  year,  this  thickening  of 
the  trunk  proceeds  without  interruption  and  homogeneously ;  no  mark 
betrays,  in  a  smooth,  transverse  section  of  the  stem,  the  time  which  was 
required  for  its  formation.  As  we  proceed  toward  the  north,  however, 
as  the  climatal  conditions  produce  continually-increasing  diversity  in  the 
particular  seasons,  the  corresponding  growth  in  thickness  shows  itself  to 
have  been  furthered  by  the  favorable  season,  and  restrained  or  altogether 
interrupted  by  the  unpropitious  times.  In  a  cross  section  of  a  stem  are 
seen,  the  higher  the  latitude  in  which  it  has  grown,  the  greater  differ- 
ences in  the  structure  of  the  successive  portions  of  the  wood,  until  final- 
ly, in  the  latitudes  where  there  is  a  severe  alternation  of  winter  and  sum- 
mer, so  striking  becomes  the  difference  between  the  wood  last  formed  in 
summer  and  that  first  produced  in  the  next  spring,  that  we  may  count, 
in  the  number  of  annular  marks  thus  produced  in  a  cross  section,  with 


ABRUPT  AND  GRADUAL  IMPRESSIONS.  483 

great  certainty  and  accuracy,  the  number  of  years  which  have  been  oc- 
cupied in  the  formation  of  the  trunk.  The  circular  lines  upon  the  cross 
section,  well  known  to  every  forester,  are  thence  called  annual  rings. 
When,  fortified  with  the  knowledge  of  this  fact,  we  compare  with  each 
other  the  trunks  of  the  conifers  which  we  obtain  from  the  various  epochs 
of  formation,  we  find  that  the  oldest  remains  exhibit  no  trace  whatever 
of  annual  rings,  but,  in  the  course  of  time,  they  become  continually  more 
defined,  so  that  lastly,  in  the  most  recent  formations — for  instance,  in  the 
upper  brown  coal — they  appear  marked  just  as  distinctly  as  in  the  trees 
now  living  in  the  same  localities." 

In  speaking  of  artificial  changes  impressed  by  culture  upon  domestic 
plants  which  have  been  converted  from  varieties  into  sub-  Difference  be- 
species,  the  importance  of  the  element  of  time  was  insisted  *ween  abrupt 

T       i  -ti  1*11  an(l  gradual 

upon.  In  the  same  manner,  in  the  changes  which  have  oc-  impressions  on 
curred  during  geological  periods,  the  successive  replacement  Plants- 
of  one  class  of  vegetable  forms  by  another,  that  element  again  obtrudes 
itself  upon  our  notice.  If  a  few  years  serve  to  establish  such  minor 
changes  as  the  perpetuation  of  varieties  into  sub-species,  what  should  be 
expected  from  the  enduring  influence  of  innumerable  centuries  ?  More- 
over, in  these  artificial  results  there  is  a  necessary  abruptness  in  the  appli- 
cation of  the  disturbance,  which  can  not  but  exert  an  unfavorable  influ- 
ence. No  time  is  afforded  to  the  organism  to  suit  itself  gradually  to  the 
force  exerted  upon  it,  none  for  acclimating  itself  to  the  external  variation. 
It  must  either  yield  at  once  or  perish.  But  how  different  as  respects 
the  method  of  application  in  the  case  of  the  organic  series !  If  it  be  de- 
cline of  temperature  that  we  consider,  how  shall  we  enumerate  the  suc- 
cessive centuries  that  must  have  elapsed  as  the  descent  was  made  from 
degree  to  degree  ?  In  these  later  times,  as  is  admitted  on  all  hands,  the 
mean  temperature  of  the  surface  could  not  decline  the  tenth  part  of  a 
Fahrenheit  degree  in  the  lapse  of  10,000  years.  Yet  the  interval  has 
transpired  during  which  there  has  been  a  gradual  descent  from  those 
high  thermometric  points  at  which  the  existence  of  organic  life  was  bare- 
ly possible,  and,  in  truth,  through  a  far  greater  range  than  that.  It  sig- 
nifies nothing  that  this  descent  might  have  been  more  rapid  the  higher 
the  degree ;  in  any  case,  it  implies  a  prodigious  interval  of  time.  Or,  if 
we  consider  variations  in  the  light  of  the  sun,  either  because  of  his  being 
a  variable  star,  or  because  of  the  gradual  clearing  up  and  improving 
transparency  of  the  atmosphere,  we  are  brought  again  to  the  same  re- 
sult— long  periods  of  time ;  for,  though  there  may  be  among  the  fixed 
stars  some  whose  periods  of  variation,  as  respects  brilliancy,  are  short, 
included  perhaps  within  a  few  days,  or  even  hours,  if  we  had  no  better 
evidence,  history  assures  that  our  sun  is  not  one  of  that  quickly-varying 
group.  Or,  again,  if  we  consider  the  changes  which  have  indisputably 


484  SECULAR   PHYSICAL   CHANGES. 

occurred  in  the  chemical  constitution  of  the  air,  the  diminution  of  its  an- 
cient amount  of  carbonic  acid,  the  reduction  of  the  mean  percentage  of 
its  vapor  of  water,  the  increase  of  its  oxygen,  these  again  are  changes  of 
a  secular  kind,  the  time  required  for  the  accomplishment  of  which  is 
wholly  beyond  our  finite  comprehension.  In  such  a  gradual  advance, 
organisms  for  many  generations  might  show  but  little  change,  yet,  in 
the  end,  the  effect  must  come  to  be  profound.  Indeed,  all  the  great  nat- 
ural effects  we  witness  are  accomplished  in  this  quiet  and  gradual  way : 
the  traces  of  tempests  and  other  catastrophes  are  very  soon  effaced,  no 
matter  how  violent  the  original  commotion  may  have  been ;  but  warmth, 
and  light,  and  moisture — causes  which  act  so  gently  that  we  might  over- 
look them — are  the  agents  which  control  the  universal  aspect  of  things. 
In  this,  as  in  other  respects,  the  strong  are  always  the  silent ;  and  in  the 
Secular  phys-  sl°w  laPse  °f  many  centuries,  by  the  gradual  operation  of 
icai  changes  at-  universal  forces  thus  gently  applied,  organic  forms  had  an 

tended  by  pro-  .  ,,  j    /  v        ±- 

ductions  and  opportunity  oi  accommodating  or  acclimating  themselves  to 
extinctions.  faQ  new  gtate,  or,  if  they  failed  to  do  so  through  some  want 
of  correspondence  in  their  structure,  they  gradually  passed  away  and  be- 
came extinct.  It  is  no  argument  against  the  transmutation  of  species, 
or  even  of  genera,  that  we  have  never  witnessed  such  an  event.  We  can 
never  witness  the  necessary  combination  of  circumstances  which  should 
bring  it  about,  above  all,  as  regards  the  needful  lapse  of  time,  the  slow 
yielding  and  accommodation  which  such  a  change  implies.  In  this,  as 
in  those  great  modifications  that  have  occurred  in  the  stratification  of 
the  globe,  the  like  of  which  has  never  been  seen  in  the  periods  of  human 
record,  our  want  of  familiarity  with  them  is  a  matter  of  very  little  mo- 
ment. The  remark  of  an  eminent  geologist  applies  with  equal  force  in 
both  cases :  "  Changes  that  are  rare  in  time  become  frequent  in  eter- 
nity." 

But  it  may  be  said  that  if  by  external  influences  the  successive  spe- 
Graduai  change  cies  and  genera  in  this  manner  arose,  we  ought  to  find, 
produ^effeSs  even  Between  those  which  are  most  closely  allied,  many  in- 
by  abrupt  crises,  termediate  forms  ;  for,  since  the  active  causes  were  gradual 
in  their  operation,  one  organism  should  pass  into  another  by  slow  de- 
grees-— so  insensibly,  indeed,  that  it  would  perhaps  be  impossible  to  indi- 
cate the  point  at  which  the  proper  transition  was  made.  Such  an  ex- 
pectation is,  however,  founded  upon  a  total  misconception  of  the  charac- 
ter of  these  progresses,  for  a  force  applied  for  thousands  of  years  may 
show  no  effect,  but  at  last  may  manifest  itself  by  an  instant  crisis.  Mul- 
titudes of  illustrations  might  be  furnished  of  this  principle ;  for  instance, 
the  motion  of  a  comet  may  be  toward  the  sun  in  a  path  which  is  almost 
a  straight  line  for  scores  of  centuries,  but  on  a  sudden  it  assumes  a  curvi- 
linear course,  and  accomplishes  its  perihelion  passage  in  perhaps  a  few 


MECHANICAL  ILLUSTRATION  OF  CRISES.  485 

hours,  and  then,  receding  from  that  luminary,  takes  a  course  not  sensi- 
bly differing  from  a  straight  line,  and  occupying  perhaps  centuries  in  its 
accomplishment.  The  variations  of  direction  and  of  velocity  are,  how- 
ever, the  necessary  results  of  the  conditions  under  which  its  movement 
is  taking  place,  and  may  be  truly  said  to  have  been  originally  included 
therein. 

This  instantaneous  or  critical  assumption  of  a  new  phase  may  also  be 
illustrated  by  the  functions  of  organic  beings.  Thus  the  Illustration 
foetal  mammal,  though  provided  with  lungs,  a  mechanism  in  from  the  life 
all  respects  ready  for  aerial  respiration,  does  not  pass  by  ° 
graduated  steps  from  placental,  which  is  truly  aquatic  breathing,  but  the 
change  takes  place  on  a  sudden  at  the  moment  of  birth.  These  and 
other  such  instances  may  therefore  satisfy  us  that  what  an  imperfect  in- 
duction would  lead  us  to  look  upon  as  a  departure  from  the  existing  rule, 
or  as  a  breach  of  the  law,  may,  in  reality,  be  nothing  more  than  the  im- 
mediate or  legitimate  consequence  of  it.  They  may  teach  us  that,  in 
the  natural  progress  of  things,  variations  do  not  necessarily  always  take 
place  in  so  gradual  a  manner  as  to  be  un distinguishable  from  stage  to 
stage,  but  sometimes  instantaneously,  and,  as  it  were,  by  a  crisis. 

Again,  this  variation  by  crises  may  be  illustrated  by  many  familiar 
mechanical  contrivances.  The  case  of  the  common  seconds  Mechanical  ii- 
striking  clock  may  furnish  an  example.  Let  us  trace  the  lustrations. 
successive  conclusions  to  which  an  ingenious  man  might  have  come  at 
the  first  introduction  of  this  instrument,  his  investigation  of  it  being  sup- 
posed to  exclude  an  inspection  of  its  parts.  After  listening  for  a  length 
of  time  to  the  beats  of  its  pendulum,  he  would  observe  that  these  suc- 
ceeded at  precisely  regular  intervals,  and  after  extending  his  examination 
through  two  or  three  thousand  of  such  occurrences,  he  would  doubtless 
feel  justified  in  coming  to  the  conclusion  that  the  construction  was  of 
such  a  nature  that  the  passage  of  successive  small  intervals  of  time  was 
indicated  by  the  occurrence  of  a  brief,  dull  sound.  His  first  conclusion, 
therefore,  would  be,  that  the  instrument  would  go  on  doing  this  continu- 
ously. 

At  the  close  of -3600  such  observations,  when  the  truth  of  his  in- 
duction appeared  to  have  become  irresistible,  his  attention  would  be  ar- 
rested, and  his  faith  in  the  correctness  and  completeness  of  the  extensive 
inductive  conclusion  he  had  just  drawn  would  be  shaken  by  hearing  one 
loud  stroke  upon  a  bell.  Now,  probably,  he  would  suspect  that  the  struc- 
ture of  the  instrument  was  such  that  it  indicated  the  lapse  of  each  3600 
minor  beats  by  one  louder  stroke.  This  would  be  his  second  and  more 
improved  induction. 

Setting  himself  to  verify  the  truth  of  this  hypothesis,  he  would  watch 
the  instrument  through  3600  beats  more,  confidently  expecting  that,  at 


486  MECHANICAL   ILLUSTKATION   OF   CRISES. 

the  conclusion  thereof,  the  hypothesis  to  which  he  had  thus  hastened 
would  be  confirmed.  True  to  the  time,  the  bell  would  again  strike,  but, 
instead  of  striking  only  once,  it  would  strike  twice.  Admonished  of  the 
hastiness  of  his  hypothesis,  our  philosopher  might  now  be  induced  to 
pause  before  he  generalized  again,  and,  after  watching  through  3600  more 
beats,  the  clock  would  strike  thrice. 

Now,  surely,  he  would  feel  absolutely  certain  of  having  reached  the 
tfde  interpretation  of  the  action  of  the  machine  at  last.  His  third  and 
corrected  conclusion  would  be  that  each  group  of  3600  beats  was  register- 
ed by  the  bell,  the  number  of  strokes  upon  which  indicated  the  number 
of  such  groups,  and  that  this  it  would  do  continuously. 

Patiently  listening  through  many  thousand  beats,  he  would  find  that 
every  thing  confirmed  his  new  and  improved  induction.  He  would  hear, 
in  their  regular  succession,  ten,  eleven,  and  twelve  strokes  made  by  the 
clock.  Of  course,  his  expectation  would  now  be  confirmed  that  at  the 
next  time  the  clock  struck  it  would  be  thirteen.  How  great  would  be 
his  surprise  to  find  it  was  only  one ! 

Perseveringly  continuing  his  examination,  he  would  reach,  at  last,  the 
true  law  regulating  the  indications  of  the  machine,  and  would  find  that 
the  partial  conclusions  to  which  he  had  successively  arrived,  and  which 
he  had  thought,  at  the  time,  to  be  substantiated  by  a  superfluity  of  facts, 
were  in  themselves  incomplete,  and  in  that  respect  erroneous ;  but  he 
would  also  observe  that  whatever  truth  there  was  in  them  was  embraced 
in  the  final  induction  that  the  machine  was  not  as  simple  as  he  had  at 
first  supposed,  and  that  the  critical  variations  which  in  succession  had 
surprised  him  were  all  embraced  in  the  original  plan  of  its  construction. 
Our  imaginary  philosopher  has  passed  through  a  mental  exercise  precise- 
ly like  that  which  is  befalling  modern  comparative  physiologists.  From 
his  labors,  disappointments,  and  eventual  success,  they  may  gather  en- 
couragement. The  clock  of  the  universe  does  not  forever  go  on  vibrat- 
ing monotonously.  A  thousand  years  upon  it  are  only  as  the  beat  of  a 
pendulum ;  but  it,  too,  has  its  periods  of  critical  variation — variations  that 
were  included  in  its  original  device. 

The  point  which  I  wish  to  impress  by  these  illustrations  is,  that  there 
A  lication  of  *s  a  definite  career  which  an  organism  must  follow,  accord- 
the  preceding  ing  to  its  exposure  to  existing  physical  conditions,  and  that, 
lon<  though  this  career  may  seem  to  be  continuous,  it  by  no  means 
follows  that  it  shall  not  exhibit  an  instantaneous  and  critical  change,  and 
that,  on  a  sudden,  the  organism  may  assume  a  specifically  new  aspect ; 
and  though,  in  what  has  thus  far  been  said,  reference  has  been  had  chief- 
Influence  of  ly  to  plants,  these  observations  all  apply,  in  like  manner,  to 
ainmals-  I  do  not  propose,  however,  to  enter  on  that  branch 
of  the  inquiry  now,  but,  as  an  illustration  of  the  influence  of 


THE   INC  A   INDIANS.  487 

physical  agents,  even  on  the  highest — man  himself — shall  offer  the  fol- 
lowing example : 

M.  D'Orbigny,  in  his  description  of  the  Inca  Indians  of  South  Amer- 
ica, remarks,  "  It  has  always  been  observed  that  the  trunk  is  case  of  the 
longer  in  proportion  than  among  other  Americans,  and  that,  Inca  Indians. 
for  the  same  reason,  the  extremities  are,  on  the  contrary,  shorter.  We 
endeavored,  at  the  same  time,  to  explain  this  fact  by  the  greater  devel- 
opment of  the  chest.  It  would  appear  that  any  part  of  the  body  may 
take  a  greater  extension  from  any  adequate  cause,  while  other  parts  fol- 
low the  ordinary  course.  An  evident  proof  of  this  fact  may  be  found  in 
the  phenomena  of  imperfect  conformation,  in  which  a  certain  part  of  the 
body,  in  consequence  of  deformity,  does  not  assume,  in  external  appear- 
ance, its  complete  natural  development,  as  we  see  in  the  trunk  of  a  dwarf, 
while  this  defect  does  not  prevent  the  extremities  from  acquiring  those 
proportions  that  they  would  have  had  if  the  trunk  had  received  its  full 
growth.  This  accounts  for  the  want  of  symmetry  in  the  persons  of 
dwarfs,  and  for  that  length  of  the  upper  and  lower  limbs  so  much  out  of 
proportion  to  the  body.  If  we  admit  this  fact,  difficult  to  contest,  why, 
in  the  case  in  question,  may  we  not  as  well  admit  that  the  chest,  from  a 
cause  which  we  shall  explain,  having  acquired  a  more  than  ordinary  ex- 
tension, might  naturally  lengthen  the  trunk  without  causing  the  extrem- 
ities to  lose  their  normal  proportion,  which  would  make  it  appear,  as  in- 
deed it  would  be,  longer  than  among  other  men  where  no  accident  can 
have  altered  the  form  common  to  the  race  ? 

"  Let  us  return  to  the  causes  which  occasion  in  the  Incas  the  great 
volume  of  chest  which  has  been  observed  in  them.  Many  considera- 
tions have  led  us  to  attribute  it  to  the  influence  of  the  elevated  regions 
in  which  they  live,  and  to  the  modifications  occasioned  by  the  extreme 
expansion  of  the  air.  The  plateaux  which  they  inhabit  are  always  com- 
prised between  the  limits  of  7500  to  15,000  feet  above  the  level  of  the 
sea.  •  There  the  air  is  so  rarefied  that  a  much  greater  quantity  must  be 
inhaled  at  each  inspiration  than  at  the  level  of  the  ocean.  The  lungs 
require,  in  consequence  of  their  great  necessary  volume,  and  of  their 
greater  dilatation  in  breathing,  a  cavity  larger  than  in  the  lower  regions. 
This  cavity  receives  from  infancy  and  during  the  time  of  its  growth  a 
great  development  entirely  independent  of  that  of  the  other  parts.  "We 
were  desirous  of  determining  whether,  as  we  might  suppose  a  priori,  the 
lungs,  in  consequence  of  their  great  size,  were  not  subject  to  extraordi- 
nary modifications.  Inhabiting  the  city  of  La  Paz,  upward  of  11,000 
feet  above  the  level  of  the  ocean,  and  being  informed  that  in  the  hospital 
there  were  constantly  Indians  from  the  populous  plateaux  still  more  ele- 
vated, we  had  recourse  to  the  kindness  of  our  countryman,  M.  Burnier, 
physician  to  the  hospital,  and  he  permitted  us  to  make  a  post  mortem 


488  EXTINCTION   OF   FORMS. 

examination  of  some  of  these  Indians  from  the  highest  regions.  In  these 
we  have,  as  we  expected,  found  the  lungs  of  an  extraordinary  dimension, 
which  the  external  form  of  the  chest  clearly  indicated.  We  remarked 
that  the  cells  were  much  larger  and  more  in  number  than  in  those  of  the 
luHgs  we  had  dissected  in  France ;  a  condition  very  necessary  to  increase 
the  surface  in  contact  with  the  ambient  fluid.  To  conclude,  we  have 
discovered,  1st.  That  the  cells  were  more  dilated ;  2d.  That  their  dilata- 
tion increases  considerably  the  volume  of  the  lungs ;  3d.  That,  conse- 
quently, they  must  have  to  contain  them  a  larger  cavity;  4th.  That, 
therefore,  the  chest  has  a  much  larger  capacity  than  in  the  normal  state ; 
5th.  That  this  great  development  of  the  chest  elongates  the  trunk  beyond 
its  natural  proportions,  and  places  it  almost  out  of  harmony  with  the 
length  of  the  extremities,  this  remaining  the  same  as  if  the  chest  had 
preserved  its  natural  dimensions." 

With  respect  to  the  doctrine  of  the  influence  of  physical  agents  on  or- 
Ar  umentfrom  gaju>zation  generally,  we  admit  without  hesitation  that  the 
the  extinction  extinction  of  forms  has  been  accomplished  through  outward 
causes,  decline  of  heat,  etc.  These  extinctions  are  intimate- 
ly connected  with  the  appearance  of  new  organisms,  and,  indeed,  are  to 
be  regarded  as  being,  with  them,  essential  parts  of  a  common  plan.  It 
would  not  appear  agreeable  to  the  mode  in  which  the  scheme  of  Nature 
is  carried  out  to  invoke  one  class  of  influences  for  the  removal  of  the 
vanishing  forms,  and  a  totally  different  one  for  the  introduction  of  the 
new-comers.  There  seems  to  be  a  better  harmony  in  the  supposition  that 
all  these  things  are  managed  upon  similar  principles,  and  that,  since  it  is 
the  failure  of  congenial  conditions  which  closes  the  term  of  life  of  a  race,  it 
was  the  suitability  of  those  conditions,  or  their  conspiring  together,  which 
gave  it  origin. 

The  influence  of  decline  of  temperature  appears  when  we  examine  par- 
influence  of  ticular  individuals  or  particular  species  either  of  plants  or  of 
decline  of  tem-  animals.  Thus  the  Virginia  cherry  attains  the  height  of  100 
feet  in  the  Southern  States,  and  is  dwarfed  to  a  shrub  of  not 
more  than  five  feet  at  the  great  Slave  Lake ;  the  nasturtium,  which  is  a 
woody  shrub  in  warm  climates,  becomes  a  succulent  annual  in  cold.  Or, 
if  we  examine  some  special  tribe  of  life,  as  Milne  Edwards  has  done  in 
the  case  of  crustaceans,  the  higher  the  temperature,  the  greater  the  lia- 
bility to  variations  of  species,  the  more  numerous  also  the  differences  of 
form,  and  the  attainment  of  a  greater  individual  size.  That  these  varia- 
tions are  the  actual  consequences  of  the  physical  conditions,  and  not 
merely  collateral  results,  is  shown  by  supplying  the  condition  that  is 
wanting.  We  can  imitate  the  natural  result,  in  an  artificial  way,  in  hot- 
houses ;  the  plants  of  the  warmest  climate  may  be  grown,  and  the  effects 
of  summer  imitated  at  any  season  of  the  year.  What  better  proof  could 


METAMORPHOSIS  OF   ORGANISMS.        i  489 

we  have  of  the  control  of  the  agent  heat  over  development,  than  the  well- 
ascertained  fact  that  the  time  of  emersion  of  larvas  depends  upon  the 
temperature  ?  The  silk-grower,  by  placing  the  eggs  of  the  insect  in  an 
ice-house,  retards  them  as  long  as  he  pleases.  The  amputated  limbs  of 
the  water-newt  can  only  be  reproduced  at  a  temperature  from  58°  to  75°. 
The  tadpole,  kept  in  the  dark,  does  not  pass  on  to  development  as  a  frog. 
In  decaying  organic  solutions,  animalcules  do  not  appear  if  light  be  ex- 
cluded. 

Upon  the  whole,  therefore,  we  conclude  that  organisms  of  every  kind, 
so  far  from  presenting  any  resistance  to  change,  are.  im-  Changes  of  or- 
pressed  without  any  difficulty  by  every  exterior  condition ;  ^nd^n0  hiva" 
and  since  existing  natural  circumstances  have  been  main-  riabie  laws, 
tained  for  a  long  time  without  any  apparent  change,  their  sameness  pro- 
duces a  sameness  in  the  order  and  manner  of  development.  But  it  should 
be  borne  in  mind  that  this  idea  of,  sameness  can  be  entertained  only  on 
an  imperfect  view  of  the  state  of  Nature,  for  there  is  scarce  one  of  those 
conditions,  to  the  sameness  of  which  we  have  been  referring,  which  has 
not,  in  reality,  undergone  slow  secular  variations ;  and  with  those  changes 
there  have  been  changes  in  the  manner  of  development. 

In  truth,  as  I  have  on  a  former  page  observed,  the  only  things  which 
are  absolutely  unchangeable  are  the  laws  of  Nature,  such,  for  instance, 
as  that  of  gravitation ;  every  thing  else  is  to  be  looked  upon  as  an  effect, 
or  as  a  changeable  phenomenon  arising  from  the  operation  of  those  laws. 
So,  therefore,  though,  in  this  chapter,  the  terms  physical  in-  Successive  met- 
fluences  and  natural  conditions  have  been  repeatedly  used,  cons^uence^f 
yet  a  higher  and  more  philosophical  view  of  the  case  brings  invariable  law. 
us  inevitably  at  last  to  the  idea  of  law ;  and  therefore  I  accept  the  in- 
terpretation of  all  these  facts,  which  has  of  late  years  been  impressing 
itself  more  and  more  strongly  and  clearly  on  the  minds  of  physiologists, 
that  the  development  of  every  organism,  from  a  primordial  cell  to  its 
final  condition,  however  elevated  that  condition  may  be,  is  the  inevitable 
consequence  of  the  operation  of  a  universal,  invariable,  and  eternal  law. 

All  animals,  no  matter  what  position  they  occupy  in  the  scale  of  na- 
ture, unquestionably  arise  in  the  first  instance  from  a  cell,  which,  possess- 
ing the  power  of  giving  birth  to  other  cells,  a  congeries  at  last  arises,  the 
size  and  form  of  which  is  determined  wholly  by  external  circumstances. 
In  all  cases,  the  material  from  which  these  cells  are  formed  is  obtained 
from  without,  and,  whatever  the  eventual  shape  of  the  structure  may  be, 
the  first  cell  is  in  all  instances  alike.  There  is  no  perceptible  difference 
between  the  primordial  cell  which  is  to  produce  the  lowest  plant  and 
that  which  is  to  evolve  itself  into  the  most  elaborate  animal.  The  mode 
of  growth,  and  the  arrangement  of  the  new  cells  as  they  come  into  exist- 
ence, determining  not  only  the  form,  but  also  the  functions  of  the  new 


490  .       METAMORPHOSIS   OF   ORGANISMS. 

being,  depend  on  the  particular  physical  conditions  under  which  the 
growth  is  taking  place.  The  germ  which  is  to  produce  a  lichen  obtains 
from  materials  around  it  the  substances  it  wants  as  best  it  may;  but 
the  germ  which  is  to  end  in  the  development  of  man  is  brought  in  suc- 
cession under  the  influence  of  many  distinct  states.  As  a  consequence 
of  this,  it  gives  rise  in  succession  to  a  series  of  animated  forms,  which,  as- 
suming by  degrees  a  higher  complexity,  end  at  last  in  the  perfect  human 
being.  At  one  time  it  was  believed  that  these  metamorphoses,  as  they 
are  termed,  are  limited  to  insects  and  frogs :  the  insect,  which  at  first 
appears  under  the  form  of  a  caterpillar  as  it  comes  from  the  egg,  and, 
passing  through  the  pupa  state,  at  last  takes  its  true  position  as  a  wing- 
ed being ;  the  frog,  which,  appearing  at  first  from  the  ovum  as  a  true 
fish,  whose  respiration  is  carried  forward  by  gills,  and  whose  life  is  lim- 
ited to  the  water,  at  last  assumes  a  new  constitution  and  a  new  organi- 
zation, breathes  by  lungs,  and  becomes  an  amphibious  reptile.  But  it 
is  now  known  that  these,  so  far  from  being  exceptions,  are  only  instances 
of  a  general  rule,  which  is,  that  all  organized  beings  shall  begin  existence 
at  the  bottom  of  the  scale,  and,  taking  on  one  type  of  life  after  another,  in 
more  or  less  rapid  succession,  end,  finally,  in  assuming  a  size  and  form 
analogous  to  those  of  the  parent  which  gave  them  birth. 

There  is  a  general  resemblance  between  the  life  of  an  individual  and 
the  life  of  a  species.  Each  has  its  time  of  birth,  its  time  of  maturity, 
its  time  of  decline ;  each  also  has  its  embryonic  states.  The  fossil  forms 
of  the  early  geological  ages  are  in  many  cases  the  embryos  of  existing 
animals.  Upon  each  all  natural  agents  have  exerted  their  effects,  push- 
ing forward  or  retarding  development ;  and  this  applies  not  only  to  an- 
imals, but  also  to  plants :  it  is  in  accordance  with  the  principles  we  are 
setting  forth  that  over  the  whole  domain  of  life  natural  forces  exert 
their  sway.  Change  the  conditions  under  which  growth  is  taking  place, 
and  you  at  once  change  resulting  form  and  function.  It  is  in  this  man- 
ner that,  on  a  small  scale,  the  horticulturist  works  in  furnishing  us  what 
are  called  improved  varieties  of  flowers  and  fruits.  It  is  in  this  manner 
that  animals,  known  to  have  been  indisputably  of  the  same  original  kind, 
assume  such  different  forms  and  characters  in  various  climates.  It  is 
true,  we  can  not  expect  in  an  abrupt  mariner  to  bring  about  such  strik- 
ing modifications  in  a  solitary  individual,  for  the  life  of  an  individual  is 
readily  destroyed,  but  not  so  the  life  of  a  race ;  and  Nature,  carrying  on 
her  operations  in  the  slow  lapse  of  centuries,  and  dealing  with  races 
rather  than  individuals,  forces  them  up  to  any  point  of  development  she 
may  desire,  but  still  the  impress  of  the  laws  under  which  they  have  been 
brought  to  that  condition  is  upon  them,  and  each  betrays,  in  the  embry- 
onic and  foetal  forms,  a  manifestation  of  the  metamorphoses  through 
which  his  race  has  run. 


RUDIMENTARY  ORGANS.  491 

Our  attention  might  here  be  directed  to  that  interesting  class  of  phe- 
nomena known  to  comparative  anatomists  under  the  title  of  Rudimentary 
rudimentary  organs—that  is  to  say,  organs  which  exist  in  an  thfh^inter- 
apparently  undeveloped  and  useless  condition,  such,  for  in-  pretation. 
stance,  as  the  mammas  of  the  male  mammalian,  or  the  subcutaneous  feet 
of  certain  snakes — for  these  are  facts  intimately  connected  with  the  sub- 
ject before  us.  It  looks  as  if  Nature  stopped  short  in  her  attempt  at 
reaching  perfection,  but  it  preves  to  us  the  constancy  of  the  plans  on 
which  she  works.  In  the  case  of  the  whale,  which,  though  apparently 
belonging  to  the  fishes,  is  a  warm-blooded  mammal  and  suckles  its  young, 
the  general  type  of  its  class  is  observed  even  down  to  minute  particulars ; 
it  is  the  attribute  of  those  belonging  to  it  that  they  shall  have  seven  cer- 
vical vertebras,  and  this  is  equally  the  case  with  the  camelopard,  with 
its  long,  graceful  neck,  and  the*  mole,  which  seems  to  have  no  neck  at 
all.  In  the  whale,  which  conforms  to  that  general  rule,  the  teeth  are, 
moreover,  found  in  the  jaw,  in  the  earlier  period  of  life,  uncut,  precisely 
as  we  find  them  at  birth  in  the  human  infant.  In  this  last  instance  we 
think  we  see  a  wise  provision  and  foresight  of  nature,  which  does  not 
give  to  man  these  masticating  organs  before  the  time  they  are  wanted ; 
but  what  are  we  to  make  of  the  former  case  ?  Man  is  not  always  a  true 
interpreter  of  the  works  of  God.  Shut  up,  as  they  are,  in  the  interior  of 
the  bony  mass  of  the  jaw,  never  to  be  developed  and  never  to  be  used, 
does  not  that  look  to  a  careless  observer  something  like  a  work  of  super- 
erogation ?  Or,  in  the  case  of  such  snakes  as  the  anguis,  typhlops,  and 
amphisbasna,  why  is  it  that  Nature  has  placed  under  the  skin  the  bony 
representatives  of  the  extremities :  the  mode  of  progression  of  those  an- 
imals is  by  the  use  of  the  ribs,  and  organs  such  as  feet  are  never  wanted. 

We  may  also  turn  to  the  other  department  of  physiology,  the  vegeta-^ 
ble  world,  and  what  do  we  there  see  ?  Rudimentary  organs  and  excess 
of  development  are  .every  where  presented.  An  attentive  examination 
of  any  flower  proves  that  we  may  with  truth  regard  it  as  a  transformed 
branch,  the  law  of  development  being  such  that  that  which  might  have 
passed  forward  to  the  condition  of  a  branch  has  turned  to  the  condition 
of  a  flower ;  or,  in  still  minuter  particulars,  we  witness  the  same  prin- 
ciple :  that  which  might  have  evolved  into  a  leaf  turns  indifferently,  as 
circumstances  may  direct,  into  a  sepal,  a  petal,  or  a  stamen. 

But  is  it  possible  that  there  is  all  this  confusion  and  want  of  precision 
in  the  works , of  Nature  ?  Not  so.  If  we  consider  rightly,  Appearance  of 
we  shall  come  to  the  conclusion  that  Nature  never  works  rudimentary 

,  ,  organs  the con- 

COntingently,  nor  resorts  to  a  sudden  contnvance  to  meet  an  sequence  of 

exigency.     All  her  operations  are  carried  forward  under  far-  law- 
reaching  and  universal  laws.     These  rudimentary  and  perhaps  useless 
organs  come  into  existence  through  a  general  plan,  of  which  they  are 


492  OF  THE   ORGANIC  CELL. 

witnesses  to  us,  if  they  subserve  no  other  duty.  They  tell  the  same 
great  fact  which  is  so  loudly  proclaimed  by  all  the  phenomena  of  the  res- 
toration of  parts  and  renovation  of  tissues,  that  the  grouping  of  orga- 
nized matter  into  definite  and  special  forms  is  not  a  wanton  or  chance  ef- 
fect, but  is  the  direct  and  inevitable  consequence  of  invariable  physical 
laws. 

Expedients  are  for  the  vacillating  and  weak,  law  is  for  the  strong.  It 
takes  from  the  merit  of  any  human  contrivance  if  the  engineer  has  to  be 
constantly  tampering  with  it  to  keep  it  going ;  we  admire  the  machine 
that  continues  its  movements  without  variation  after  it  has  left  its 
maker's  hand.  I  think  we  can  have  no  nobler  conception  of  the  great 
Author  of  the  wonderful  forms  around  us  than  to  regard  them  all,  the 
vegetable  and  animal,  the  living  and  lifeless,  the  earth,  and  the  stars,  and 
the  numberless  worlds  that  are  beyond  our  vision,  as  the  offspring  of 
one  primitive  idea,  and  the  consequences  of  one  primordial  law. 


CHAPTER  III. 

OF  THE  ORGANIC  CELL :   ITS  DEVELOPMENT,  REPRODUCTION,  AND  DIF- 
FERENTIATION OF  STRUCTURE  AND  FUNCTION. 

Simple  and  Nucleated  Cells. —  The  Simple  Cell:  its  Parts  and  Functions. —  The  Nucleated  Cell: 
its  Parts  and  Functions. — Activity  of  the  Nucleus. — Other  Forms  of  Cells. —  Cells  arise  by 
Self-origination  and  Reproduction. — Reproduction  by  Subdivision  and  Endogenously. 

The  Animal  Cell. — Forms  of  Cellular  Tissue. — Forms  of  Vascular  Tissue. — Spiral  Vessels, 
Ducts,  etc. 

Differentiation  of  Cells. — Acquisition  of  new  Functions. — Differentiation  of  the  Animal  Cell. — 

Depends  on  Physical  Causes. — Influence  of  Heat  and  Air. — Epoch  of  Differentiation. 

• 

THE  organic  cell,  which  is  the  starting-point  of  every  organism,  veg- 
Simpieandnu-  etable  or  animal,  consists  of  a  vesicle  or  shell,  with  included 
cieated  cells,  contents.  If  the  vesicle  be  of  uniform  thickness  all  over, 
the  cell  is  a  simple  one ;  but  if  there  be  upon  some  portion  of  it  a  thick- 
ened granular  spot,  the  cell  is  said  to  be  nucleated. 

The  vesicle  of  the  SIMPLE  VEGETABLE  CELL,  more  closely  examined, 
The  simple  ^s  found  to  be  composed  of  different  laminas  or  strata.  The 
vegetable  cell:  innermost,  designated  the  primordial  utricle,  consists  of  an 

its  wall,  utri-  .     '  _        &  ••  /.  , 

cie,  and  endo-  azotized  substance,  a  member  01  the  protein  group.  On  the 
chrome.  exterior  of  this  pellicle,  and,  as  it  were,  arising  from  its  sur- 

face, lies  the  cell  wall,  which  serves  to  give  protection  to  the  parts  with- 
in. The  cell  wall  is  not  a  mere  extension  by  thickening  of  the  primor- 
dial utricle,  as  is  proved  by  its  chemical  constitution  ;  for,  though  it  may 
vary  in  physical  condition  from  a  mere  glairy  mucus  to  a  firm  woody 


THE   NUCLEATED   CELL.  493 

texture,  it  uniformly  consists  of  a  non-nitrogenized  body,  gummy,  amy- 
laceous, or  ligneous.  Indeed,  though  the  vegetable  cell  is  usually  said 
to  have  two  concentric  investitures,  the  nitrogenized  primordial  utricle 
and  the  non-nitrogenized  wall,  it  is  more  exact  to  describe  the  latter  as 
consisting  of  several  pellicles,  which  have  been  generated  in  succession 
from  the  outside  surface  of  the  utricle,  and  these  differ  from  one  another 
in  their  physical  qualities,  according  as  they  are  nearer  to  the  surface  of 
the  utricle  or  nearer  to  the  general  exterior,  recalling,  in  this  respect,  the 
analogous  condition  of  the  cuticle  under  circumstances  that  are  some- 
what parallel. 

Within  the  primordial  utricle,  the  cell  contents  present  themselves  of 
a  different  nature  and  different  form,  according  as  the  species  of  the  cell 
may  be.  In  different  cases  they  are  colored  of  various  tints,  and  are  of 
various  consistency,  more  solid  or  more  liquid.  To  the  cell-contents  the 
convenient  designation  of  endochrome  is  given.  This  interior  content  is 
not  to  be  understoodas  having  a  homogenous  constitution,  since  sometimes 
even  its  colored  portions  are  separated  out  and  arranged  in  dots  or  spiral 
lines,  which  are  very  distinct  from  the  remaining  uncolored  material. 

The  active  portion  of  such  a  cell  consists  of  the  utricle  and  endochrome 
conjointly,  the  cell  wall  only  discharging  a  mechanical  office.  In  the 
simple  cell,  all  parts  of  the  utricle  appear  to  be  endowed  with  equal  pow- 
er for  carrying  on  the  functions  of  the  organism. 

But  in  those  cells  which  possess  a  nucleus,  the  energy  is  no  longer  dif- 
fused with  uniformity,  the  nucleus  concentrating  much  of  «, 
the  power  in  itself,  and  serving  as  a  centre  of  activity.     Its  activity  of  its 
nitrogenized  constitution  indicates  that  it  is  in  relation  with  nucleus- 
the  primordial  utricle,  and  not  with  the  cell  wall ;  a  conclusion  which  is 
corroborated  by  its  physiological  activity,  as  also  by  the  fact  that  in  those 
nucleated  cells  which  exhibit  currents,  the  nucleus  appears  to  be  the 
starting-point  from  which  they  diverge  in  various  directions. 

There  are  subordinate  species  of  cells,  as  the  spiral  and  the  dotted. 
These  exhibit  points  of  re-enforcement  or  thickening,  such  Subordinate 
as  the  appearance  of  a  thread  wound  spirally,  or  in  dots  here  forms  of  cells- 
and  there  on  the  interior  of  the  wall.  There  would  seem  to  be  a  tend- 
ency during  the  development  of  a  cell  for  these  parts  to  assume  a  spiral 
arrangement.  Even  the  endochrome  shows  this  peculiarity,  the  green 
material  being  often  arranged  in  a  spiral  course  on  the  interior  of  the  cell. 

Thus  constituted,  each  cell  runs  through  a  definite  cycle  or  career,  hav- 
ing its  moment  of  birth,  its  period  of  maturity,  its  time  of  death.  Dur- 
ing its  mature  life  it  discharges  with  activity  the  special  function  to  which 
it  is  devoted,  but  in  so  doing  becomes  eventually  worn  out  and  old. 
The  period  of  activity  of  cells  of  different  species  is  very  different,  some 
passing  away  quickly,  and  others  having  a  longer  duration. 


494  REPRODUCTION   BY  SUBDIVISION. 

The  commencement  of  cells  is  either,  1st,  by  self-origination,  or,  2d, 
by  reproduction.     1st.  Cells  arise  in  an  obscure  manner  from 

Origin  of  cells       J       r  •  t        n        •        • 

byseif-origina-  homogeneous  particles  floating  in  a  protoplasma,  which,  tak- 
tion.  jng  on  Development,  have  a  vesicle  thrown  over  them,  and, 

being  of  a  spherical  shape,  present  the  aspect  of  a  cell  wall  and  cavity. 
The  granular  content  by  degrees  increases  as  the  young  cell  grows  in  all 
its  dimensions.  From  that  granular  content  new  cells  may  arise. 

Though  this  process  is  spoken  of  as  one  of  self-origination,  it  is  quite 
probable  that  the  spherical  and  homogeneous  particles  floating  in  the 
protoplasma,  and  which  were  the  points  of  origin  of  the  cells  that  have 
arisen,  were  themselves  nothing  more  than  germs  which  had  been  pre- 
pared by  an  antecedent  generation  of  cells.  This  is  the  opinion  com- 
monly entertained  of  their  nature,  though  its  truth  has  never  yet  been 
demonstrated  by  actual  observation.  It  is  adopted  because  of  its  proba- 
bility, for  we  usually  observe  that  every  new  organism  is  the  descendant 
of  an  older  one ;  yet  it  should  not  be  forgotten  that  there  must  have  been 
a  time  when  the  first  organic  cell  arose  from  inorganic  material,  and  it  is 
not  unphilosophical  to  suppose  that  what  must  have  occurred  once  may 
occur  again. 

Origin  of  cells  .  2d.  Cells  are  reproduced  from  antecedent  ones  of  the 
by  reproduction.  same  kind  by  subdivision,  by  budding,  by  endogenous  gen- 
eration. 

The  reproduction  of  cells  by  subdivision  is  strikingly  illustrated  by 
Reproduction  theHasmatococcus  binalis.  The  manner  of  the  process  seems 
by  subdivision.  f0  be  as  follows.  The  endochrome  of  the  original  spherical 

cell,  «,  Fig.  230,  begins  to  undergo  bi-par- 
tition  as  at  b,  and  as  the  dividing  portions 
recede  from  one  another  the  primordial  utri- 
cle bends  round  them.  Next  a  layer  of  per- 
manent  cell  wall,  of  a  mucous  character  on 
its  exterior,  is  produced,  which  accompanies 
the  inflection  of  the  primordial  utricle  as  at 
}e  c,  and,  after  a  while,  the  bi-partition  is  com- 
plete, and  the  separated  portions  constitute 
distinct  individual  cells.  The  subdivision 
may  be  repeated  as  at  d.  The  seat  of  the 

Reproduction  of  H^matococcus  binalis.     primarv   acti(m    fe    gaid    to    be    in   the    endo_ 

chrome  ;  but  of  this  there  may  be  reasonable  doubt,  since  generally  the 
primordial  utricle  is  the  place  of  energy  of  the  cell ;  and  where  nucleated 
cells  undergo  multiplication  by  this  process  of  fissure,  the  nucleus  di- 
vides along  with  the  endochrome,  so  that  both  the  resulting  portions  pos- 
sess a  part  of  it.  But  if  the  utricle,  with  its  nucleus,  was  inert  during 
this  operation,  it  would  seem  that  the  vesicle  should  tear  any  where 


KEPRODUCTION   BY  BUDDING. 


495 


rather  than  through  that  thickened  and  stronger  place.  The  phenomena 
are  equally  well  accounted  for  by  imputing  the  first  action  to  the  utricle 
itself,  which,  exerting  a  constrictive  pressure  upon  the  endochrome  in  the 
direction  of  one  of  the  great  circles  of  the  cell,  divides  it  in  the  manner 
that  we  see. 

This  process  of  multiplication  is  exhibited  in  Fig.  231,  in  Conferva 


Fig.  231. 


Cell  reproduction  in  Conferva  glomerata. 

glomerata,  which  consists  of  a  system  of  cells  arranged  in  a  filament.  At 
A  two  states  are  shown,  complete  partition  at  £,  and  incomplete  at  a  /  at 
B,  C,  D,  the  successive  steps  of  partition,  a  being  the  primordial  utricle, 
b  the  endochrome,  c  cell  membrane,  d  mucous  investment.  At  E  the 
primordial  utricles  are  separated,  and  the  cell  membrane  intervenes.  At 
F  the  membrane  is  completed  so  as  to  exhibit  lamina. 

The  cells  which  have  thus  arisen  by  subdivision  soon  grow  to  the 
size  of  the  one  from  which  they  were  derived,  and  are  ready  for  subdi- 
vision in  their  turn.  Indeed,  it  often  happens  that  traces  of  incipient 
subdivision  may  be  detected  long  before  the  cell  has  reached  its  mature 
dimensions. 

The  reproduction  of  cells  by  budding  may  be  illustrated  by  the  vesi- 
cles of  the  yeast-plant ;  and  though,  in  those  cases  in  which  the  budding 
cell  possesses  a  nucleus,  the  nucleus  is  not  necessarily  involved,  yet  the 
conclusion  indicated  in  the  preceding  paragraph  is  greatly  strengthened, 
for  we  must  clearly  attribute  the  result  which  now  takes  place  to  an  in- 
creased nutrition  of  the  primordial  utricle  upon  a  restricted  portion  of 
its  surface,  and  not  to  a  distention  arising  from  a  pressure  of  the  endo- 
chrome within.  So  closely  does  this  resemble  the  preceding  mode  of  re- 
production, that  they  are  commonly  said  to  be  really  of  the  same  kind, 
or,  rather,  to  offer  no  other  distinction  than  this,  that  in  the  former  the 


496  THE   ANIMAL   CELL. 

cell  divides  into  portions  which  are  sensibly  equal,  in  this  into  unequal 
parts. 

Cells  are  said  to  arise  from  endogenous  generation  when  they  make 
their  first  appearance  in  the  cavity  of  a  former  cell,  of  which 

Endogenous  Jrir  .  *.  .  . 

generation  of  the  endochrome  exhibits  a  disposition  to  divide  into  many 
small  portions,  at  first  doubtfully,  then  more  distinctly,  and 
each  one  of  these  portions  obtaining  a  covering  investiture  or  primordial 
utricle  for  itself.  The  process  continues  until  the  young  brood  of  cells 
has  reached  a  certain  degree  of  perfection,  when  they  -escape  from  their 
confinement,  either  by  the  fissuring  or  deliquescence  of  the  old  cell  wall. 
The  young  cells  may  now  lead  an  independent  life  and  grow  rapidly. 
In  this  manner  zoospores  arise,  which  are  young  cells  having  for  a  time 
a  power  of  locomotion,  from  cilia  which  have  been  developed  from  their 
walls,  or  for  other  reasons. 

The  reproduction  of  cells  l>y  endogenous  generation  is  commonly  at- 
tributed to  an  action  arising  in  the  endochrome  which  brings  on  its  sub- 
division into  portions.  From  the  fact  that  these  portions  are  eventually 
found  clothed  with  a  primordial  utricle,  we  might  be  led  to  suspect  that 
the  original  seat  of  the  action  is  in  this,  as  in  the  preceding  cases,  that 
portion  of  the  original  cell  which,  undergoing  projection  internally,  di- 
vides the  endochrome  and  incloses  the  portions  in  its  meshes.  Such 
membranous  projections  may  be  difficult  of  detection  in  the  first  instance, 
because  of  their  extreme  tenuity ;  nor  is  the  fact  that  the  zoospores 
move  freely  in  the  cavity  of  the  mother  cell  just  before  their  escape  at 
all  in  contradiction  to  this. 

THE  ANIMAL  CELL  presents  a  structural  arrangement  diifering  from 
Peculiarity  of  the  vegetable  in  this,  that  it  does  not  possess  a  proper  cell 
the  animal  cell.  wall,  but  consists  of  a  primordial  utricle  and  interior  con- 
tent alone.  Its  manner  of  reproduction  is  of  three  kinds :  1st.  From 
germs ;  2d.  By  fissure ;  3d.  Endogenously.  Where  animal  cells  orig- 
inate from  germs,  these  seem  to  be  granules  of  a  substance  analogous  to 
fibrin,  which  are  floating  in  the  formative  liquid.  In  duplication  by  sub- 
division, the  import  of  the  nucleus  is  shown  by  the  fact  that  the  action 
begins  at  it.  It  may  be  said  of  animal  cells  that  the  nucleus  maintains 
a  more  conspicuous  relation  than  it  does  in  the  case  of  vegetable  ones. 
Reproduction  in  the  endogenous  manner  is  carried  forward  in  the  case  of 
these  cells  in  the  manner  described  in  a  preceding  paragraph. 

OP   THE  CONSTRUCTION  OP   CELLULAR  AND  VASCULAR  TISSUES. 

By  their  development  and  juxtaposition  with  one  another,  cells  give 

Cellular  tissue   r*se  to  coirtinuous  fabrics  of  various  kinds,  or  cellular  tissue. 

its  various        If  the  development  of  new  cells  occurs  in  a  space  where  there 

is  freedom  from  pressure,  the  cells  maintain  their  original 


CELLULAR   TISSUE. 


497 


Fig.  232. 


spherical  form,  as  seen  in  the  photograph,  Fig.  232.     But  should  the 

development  occur  in  a  confined  space, 
or  under  circumstances  of  pressure,  the 
intercellular  spaces  which  necessarily  ex- 
ist in  the  former  case  by  reason  of  the 
spherical  shape,  are  now  encroached  upon, 
and  the  cells  assume  various  angular 
forms,  such  as  parallelopipedons,  rhom- 
bic dodecahedrons,  &c.  Of  the  former 
we  have  an  example  in  the  photograph, 
Fig.  233,  which  represents  a  section  of 
muriform  cellular  tissue.  In  other,cases, 
with  a  view  of  giving  resistance  to  press- 
simple  cellular  tissue,  magnified  50  diameters.  ^  the  interior  of  each  Of  the  Cells  is 

fortified  by  a  fibre,  and  thus  arises  the  tissue  of  which  we  have  an  exam- 

Fig.  23.4. 
Fig.  233. 


Muriform  cellular  tissue,  magnified  50  diameters. 


Fibro-cellular  tissue,  magnified  50  diameters. 


pie  in  the  photograph,  Fig.  234.  Two  or  more  fibres  may,  in  this  man- 
ner, be  employed,  and  when  such  is  the  case,  it  is  observed  that  they  do 
not  cross  one  another,  the  one  winding  from  right  to  left,  the  other  from 
left  to  right,  but  they  are  laid  parallel  to  each  other,  and  form  a  com- 
pound strand.  In  other  cases  the  constituent  cells  of  the  tissue  assume 
much  more  complicated  forms,  as,  for  instance,  in  the  stellate  variety. 
These  more  complicated  forms  prove  that  it  is  not  altogether  through 
the  influence  of  a  force  of  compression  that  cells  assume  modified  shapes, 
but  that  on  many  occasions  the  disposition  of  their  primordial  utricle  to 
branch  in  various  directions,  of  which  mention  has  been  made  in  a  pre- 
ceding paragraph,  is  the  true  cause  of  the  variations  in  question. 

This  disposition  to  grow  spontaneously  in  one  direction  rather  than  in 
another  is  the  cause  of  the  production  of  the  different  kinds  of  vascular 
tissue.  A  cell  undergoing  extreme  elongation  in  one  direction,  either  by 

II 


498 


VASCULAE   TISSUE. 


reason  of  this  quality  of  its  primordial  utricle,  or  through  un- 
Vascular  tissue  * 

and  its  modifi-  equal  nutrition,  or  other  cause,  gives  origin  to  a  tube.  And 
if,  of  several  cells  thus  elongated,  and  placed  end  to  end  on 
each  other,  the  terminal  portions  should  be  obliterated  either  by  rup- 
ture or  absorption,  a  vessel  permeable  throughout  is  the  result.  In  this 
manner  vascular  tissue  arises.  These  vessels  still  exhibit  the  structural 
peculiarity  of  the  cells  from  which  they  have  originated  in  this,  that  they 
may  be  fortified  in  their  interior  with  fibres  wound  in  a  spiral,  and  so 
constituting  a  spiral  vessel ;  or  wound  in  rings,  and  forming  annular 
ducts.  In  like  manner,  through  similar  modifications,  the  varieties  known 
as  reticulated  and  dotted  ducts  arise.  In  these  fibre-vascular  tissues  it 
frequently  happens  that  the  fortifying  thread  is  double  or  even  quadru- 
ple. Of  spiral  vessels  derived  from  a  cactus  we  have  an  example  in  the 
photograph,  Fig.  235,  and  in  those  from  the  banana  in  that  of  Fig.  236. 


Fig.  236. 


Fig,  235. 


Spiral  vessels  of  cactus,  magnified  50  diameters. 


Spiral  vessels  of  banana,  magnified  50  dinmctcrs. 


The  spiral  vessels  of  plants  Contain  air.  Other  tubes  are  for  the 
Spiral  vessels,  conveyance  of  liquid;  the  laticiferous  vessels,  for  example, 
v  "f'co-  which  are  branching  tubes  Fi,.  237. 

nifers.  for  transmitting  the  latex 

of  plants.  Again,  in  other  cases,  the 
interior  of  the  vessel  is  more  or  less 
completely  filled  up  by  a  gradual  de- 
posit of  solid  material,  it  being  in 
this  manner  that  proper  woody  fibre 
is  formed  from  long,  spindle-shaped 
cells.  Vascular  tissue  in  coniferous 
plants  presents  a  peculiar  dotted,  as- 
pect from  disc-like  forms,  exhibiting 
a  pair  of  concentric  circles,  which  are 
set  at  regular  intervals  upon  it,  as 
shown  in  the  photograph,  Fig.  237, 


Woody  fibre  of  pine,  magnified  50  diameters. 


YELLOW  AND  WHITE   FIBROUS   TISSUE. 


499 


which  is  dotted  woody  fibre  from  pine.  The  circular  discs  or  glands  run 
in  single  rows  except  in  one  place,  where  a  double  row  is  seen.  Among 
true  living^  pines  more  than  two  rows  are  not  met  with.  In  the  Arauca- 
ria  the  rows  are  sometimes  triple  or  even  quadruple. 

Animal  vascular  tissue  arises  in  the  same  manner  as  vegetable,  by  the 
conjunction  of  elongated  cells  and  the  obliteration  of  their  v ,, 

°  .  Yellow  and 

terminations.  The  physiological  purposes  these  vessels  sub-  white  fibrous 
serve  are,  as  in  the  other  instance,  the  conveyance  of  gases  or  tlssue< 
liquids.  But  fibres  may  form  in  animal  fabrics  without  the  previous  in- 
termedium of  cells,  either  directly  from  fibrin,  the  parts  of  which  possess 
the  quality  of  agglutinating  into  threads,  or  from  the  coalescence  under 
like  circumstances  of  substances  allied  to  gelatine,  which  yield  the  varie- 
ties of  fibrous  tissue  known  respectively  as  the  yellow  and  the  white, 
the  former  being  composed  of  branching  filaments,  as  seen  in  Fig.  238. 
It  is  unacted  upon  by  warm  acetic  acid,  and,  from  its  extraordinary  elas- 

Fig.  23S.'  Fig.  289. 


represented  i 


Yellow  fibrous  tissue,  magnified  300  diameters.       White  fibrous  tissue,  magnified  300  diameters. 

ticity,  is  used  wherever  that  quality  is  required.     The  latter,  which  is 
.  239,  shows  strands  of  a  wavy  appearance:  it  is  inelas- 
240.  tic,  softens  under  the  action  of  acetic  acid, 

being  thereby  distinguished  from  the  pre- 
ceding, and  is  employed  on  account  of 
its  tenacity  wherever  resistance  to  exten- 
sion is  required,  as,  for  example,  in  the 
ligaments  of  the  joints.  The  solid  ani- 
mal fibres  are  therefore  employed  where 
physical  qualities  are  necessary,  the  hol- 
low tubes  for  organic  processes.  By 
some  physiologists  it  is  believed  that 
both  yellow  and  white  fibrous  tissue  arise 
from  cells. 

Areolar  tissue,  magnified  25  diameters.  Areolai*  01'  Connective  tisSUC.  Fig.  240, 


50Q  DIFFERENTIATION   OF  CELLS. 

is  composed  of  the  two  preceding  elements,  the  yellow  and  white  fibrous, 
interwoven  with  each  other  so  as  to  constitute  a  porous  structure,  with  a 
multitude  of  intercommunicating  spaces.  It  is  to  be  understood  that 
these  interstices  are  wholly  distinct  from  cells;  hence  the  inapplicability 
of  the  term  cellular,  sometimes  employed  for  this  tissue.  Areolar  tissue 
is  employed  for  uniting  the  various  animal  parts.  Its  interspaces  are 
filled  with  a  fluid,  which,  when  in  jexcess,  is  spoken  of  as  dropsical  effu- 
sion. Air,  artificially  or  accidentally  introduced  at  any  point  into  it,  may 
pass  to  every  part,  as  is  illustrated  in  cases  of  emphysema.  The  speci- 
men from  which  the  figure  is  taken  was  in  this  manner  inflated. 

By  the  differentiation  of  cells  is  meant  the  assumption  of  a  variation 
Differentiation  in  their  structure  from  which  follows,  as  a  consequence,  the 
of  cells.  capacity  of  discharging  new  functions.  When  the  red  snow- 

alga  multiplies,  as  previously  described,  each  of  the  young  cells  resem- 
bles that  from  which  it  was  derived  in  structure,  and  discharges  a  simi- 
lar office.  In  such  a  case  there  is  development,  but  not  differentiation. 
When,  on  the  contrary,  a  lichen  grows  on  a  rock,  though  the  original 
tendency  in  development  may  have  been  for  the  production  of  cells  from 
the  first  germ  absolutely  similar  in  all  directions,  yet  the  circumstances 
of  growth  are  such  that  very  soon  the  physical  conditions  under  which 
the  cells  of  different  parts  of  the  growing  mass  are  generated  become  dif- 
ferent. Those  which  are  next  to  the  rock  are  screened  by  the  superin- 
cumbent ones  from  the  sunlight  and  the  air ;  they  are  therefore  develop- 
ed in  a  comparative  obscurity,  and  in  the  presence  of  moisture  holding  in 
Acquisition  of  solution  inorganic  salts.  Under  such  circumstances,  it  is  to 
new  functions,  "foe  expected  that  a  modification  will  ensue  in  their  construc- 
tion, and  that  they  will  be  different  from  those  which  are  developing  on 
the  exterior  in  contact  with  the  dry  air ;  and,  since  a  change  of  structure 
invariably  implies  a  change  of  function,  we  might  expect,  as  in  reality  is 
the  case,  that  the  outer  cells  are  for  the  obtaining  of  carbon  from  the  air, 
being  acted  upon  by  the  sunlight,  and  the  under  cells  for  procuring  moist- 
ure and  such  saline  substances  as  may  be  wanted  from  the  rock  surface 
below.  In  such  a  case  as  this  there  is  a  differentiation  both  of  structure 
and  of  function. 

Structural  differentiation  is  to  be  received  as  the  cause  of  functional 
Differentiation  differentiation,  which  is  its  consequence.  The  former,  in 
in  a  regular  se-  every  instance,  arises  from  the  changed  circumstances  under 

quenceappears  J.  \.  i-t^-       i  c    - 

to  be  determ-  which  cells  are  being  generated,  and  if  this  change  of  circum- 
med  by  law.  stances  follows  a  regular  order  or  sequence,  the  differentia- 
tion will  assume  the  appearance  of  being  guided  by  a  fixed  law.  Many 
physiologists,  who  have  not  been  disposed  to  accord  to  physical  agents  a 
due  influence  in  this  respect,  have  therefore  imputed  to  the  developing 
cell  a  power  or  property  of  spontaneously  pursuing  a  determinate  career. 


DIFFERENTIATION   OF  ANIMALS.  501 

It  is  clear  that  the  facts  are  capable  of  interpretation  either  upon  the  doc- 
trine that  external  conditions  guide  or  compel  the  cell  in  its  development- 
al career,  or  that  it,  by  reason  of  an  innate  power,  spontaneously  pursues 
a  determinate  course  in  spite  of  them ;  determinate,  because  that  power 
is  acting  under  a  law.  The  mixed  doctrine,  which  imputes  the  career  of 
development  in  part  to  the  innate  power  of  the  cell,  and  in  part  to  the  in- 
fluence of  external  conditions,  it  is  needless  for  us  here  to  consider. 

No  doubt  can  be  entertained  of  the  fact  that  a  cell  or  congeries  of  cells 
will  differentiate  when  submitted  to  new  physical  conditions  while  in  the 
act  of  development.  Thus  certain  lichens  pass  into  forms  analogous  to 
algae  if  the  normal  conditions  of  their  production  be  reversed — if,  instead 
of  developing  in  places  that  are  dry  and  brightly  illuminated,  they  are 
supplied  with  moisture,  and  made  to  grow  in  obscurity;  and,  in  like  man- 
ner, some  of  the  fungi  will  simulate  algse  if  they  are  compelled  to  vege- 
tate in  water. 

The  separation  of  the  organ  for  the  reception  of  water  and  that  for  the 
reception  of  carbon,  which  is  first  shadowed  forth  in  the  under  and  outer 
surface  of  the  lichens,  is  manifested  in  perfection  by  highly-developed 
plants,  in  which  the  root  discharges  the  former,  and  the  leaves  the  latter 
duty,  and  these  are  separated  widely  apart  from  each  other  by  the  as- 
cending axis  or  stem. 

The  remarks  here  made  respecting  plants  might  be  repeated  as  re- 
gards animals,  which,  during  their  development,  exhibit  the  Differentiation 
principle  of  differentiation  even  in  a  more  striking  way.  of  the  animal 
Thus,  in  the  protozoa,  as  in  the  protophyta,  cells  undergo  cel1' 
duplication,  and,  by  development  in  new  positions,  or  under  changed  cir- 
cumstances, exhibit  differentiation.  The  trivial  circumstances  under 
which  new  functions  are  assumed  are  well  shown  in  Trembley's  experi- 
ments with  the  hydra*  This  polype,  which  is  nothing  more  Experiments 
than  a  gastric  sac  furnished  with  prehensile  tentacles,  re-  with  the  hydra, 
spires  on  its  outer  surface  and  digests  on  its  inner;  but  so  closely  are 
these  functions  blended  together  that,  if  the  animal  be  turned  inside  out, 
the  surface  that  did  respire  will  now  digest,  and  that  which  did  digest 
will  now  respire.  Indeed,  we  may  in  an  ideal  manner  con-  Ideal  differen_ 
ceive  of  the  production  of  the  more  elementary  animal  forms  tiation  of  ani- 
as  arising  from  a  simple  sac  or  bag,  which,  furnishing  a  start- 
ing-point, exhibits  its  first  acquirement  of  localization  of  function  by  the 
doubling  of  one  half  into  the  other,  thereby  giving  rise  to  a  cup  or  pocket 
shaped  form,  so  that  respiration  and  digestion,  which  were  confusedly  and 
conjointly  carried  forw'ard  upon  the  same  surface,  are  now  parted  from 
each  other,  the  outside  of  the  cup  being  devoted  to  the  one,  and  the  in- 
side to  the  other.  Increased  endowments  are  obtained  by  crimping  or 
dividing  the  edge  of  the  cup,  prehensile  organs  of  less  or  greater  length 


502  CAUSE   OF   DIFFERENTIATION. 

and  power  thereby  arising ;  and  this,  in  reality,  is  the  structure  of  the 
hydra  just  alluded  to.  Another  advance  is  made  by  the  preparation  of 
new  and  complicated  structures,  fashioned  out  in  the  substance  between 
the  inner  and  the  outer  wall,  and  in  this  manner  arise  the  various  mech- 
anisms for  respiration  and  reproduction.  Such  a  state  of  things  is  pre- 
sented by  the  Actinia. 

It  will  be  found,  when  we  describe  the  development  of  the  higher  ani- 
Individuai  and  mals,  that  a  parallelism  is  observed  between  the  career  of 
race  develop-  Q^h  individual  and  that  of  the  series  to  which  it  belongs, 
niais  by  differ-  The  evidence  furnished  by  natural  history  and  paleontology 
entiation.  proves  that,  in  the  development  of  animal  species,  there  has 
been  an  orderly  progress,  not  so  much  from  those  of  a  lower  to  those  of 
a  higher  form,  as  from  the  general  to  the  special ;  a  gradual  parting  out 
of  structures  and  functions  that  were  once  commingled  and  coalesced,  an 
elaboration  which  may  be  attributed  either  to  a  melioration  of  the  cir- 
cumstances under  which  species  were  successively  forming,  or  to  the 
innate  power  possessed  by  the  organic  structure  itself.  Even  at  the  pres- 
ent time  our  knowledge  of  the  order  of  geological  change  is  sufficiently 
exact  to  enable  us  to  institute  an  inquiry  into  the  probability  of  the  cor- 
Differentiation  rectness  of  each  of  these  hypotheses,  upon  the  principle  that, 
dhP  8?crf°dr  smce  there  is  that  parallelism  between  the  career  of  individ- 
cumstances.  ual  development  and  race  development,  there  should  also  be 
an  analogy  in  the  physical  circumstances  under  which  they  have  taken 
place.  Among  conditions  in  animal  development,  two  prominent  ones 
may  be  mentioned  ;  they  are  the  degree  of  temperature  at  which  the  pro- 
cess is  carried  forward,  and  the  quality  or  nature  of  the  medium  supplied 
for  respiration.  No  doubt  can  now  exist  that,  as  regards  the  former, 
there  has  been  a  gradual  diminution  from  the  early  times,  and  that,  as 
respects  the  latter,  the  quantity  of  oxygen  furnished  in  the  medium  of 
respiration  has  been  increased.  It  has  long  been  observed,  in  a  general 
way,  that  there  is  a  correspondence  between  the  activity  of  respiration 
and  the  degree  of  animal  endowment,  both  as  regards  the  individual  and 
Influence  of  ^e  race>  The  provision  made  for  the  more  perfect  conduc- 
the  aerial  tion  of  the  process  from  the  moment  that  the  embryo  exhibits 
any  arterialization  of  its  blood,  is  always  attended  with,  if  it 
is  not  the  cause  of,  increasing  animal  power.  The  supply  of  oxygen  at 
the  first  period  is  very  imperfect,  but  instrumental  means  are  introduced 
in  succession  to  increase  the  amount.  When  a  mere  membrane  has  be- 
come insufficient  to  meet  the  requirements,  branchiaB  are  resorted  to,  and 
these,  in  their  turn,  are  replaced  by  lungs.  In  a'  double  way,  therefore, 
an  increased  supply  is  secured,  by  alterations  in  the  mechanism  obtain- 
ing it,  which  gradually  becomes  more  and  more  adapted  to  the  end  in 
view,  or  by  variations  in  the  chemical  constitution  of  the  medium  which 


INFLUENCE   OF   EXTERNAL   AGENTS.  503 

furnishes  it.  Thus,  in  the  development  of  a  mammal,  the  first  and  lim- 
ited supply  of  oxygen  is  from  the  portion  contained  in  the  liquids  of  the 
ovum  ;  a  far  more  copious  one,  at  a  later  period,  is  derived  from  the  pla- 
cental  mechanism  ;  but  these  subordinate  states  eventually  give  place  to 
the  direct  respiration  of  the  open  atmospheric  air.  As  this  gradual  march 
in  the  evolution  of  the. respiratory  function  is  going  forward,  it  is  attend- 
ed by  a  corresponding  development  of  all  the  animal  capabilities. 

So,  too,  on  the  great  scale  with  genera  and  species.  In  the  impure  at- 
mosphere of  the  earliest  geological  times,  it  was  not  possible  that  energet- 
ic respiration  could  be  carried  on  either  by  aquatic  or  by  aerial  animals. 
Both  may  be  included  in  the  remark,  for  it  is  demonstrable  that,  on  ordi- 
nary physical  principles,  there  must  ever  be  a  correspondence  between  the 
chemical  constitution  of  the  atmospheric  air  and  the  gas  of  respiration 
dissolved  in  the  sea,  or  other  natural  waters.  Abundant  geological  evi- 
dence is  before  us  to  the  effect  that  the  entire  respiratory  medium,  both 
atmospheric  and  aquatic,  has  passed  through  a  gradual  amelioration,  the 
percentage  amount  of  its  irrespirable  elements  declining,  and  that  of  its 
oxygen  correspondingly  increasing.  The  removal  of  those  prodigious 
masses  of  carbon  deposited  as  coal  satisfactorily  establishes  this  point ; 
and,  therefore,  as  far  as  that  medium  is  concerned,  there  is  a  general  re- 
semblance between  the  conditions  under  which  the  entire  animal  series 
and  the  single  individual  have  been  placed. 

We  might  include  in  these  remarks  the  vegetable  as  well  as  the  ani- 
mal series ;  for,  as  respects  flowering  plants,  it  is  the  special  function 
of  their  floral  or  reproductive  apparatus  to  discharge  at  a  particular  epoch 
the  functions  of  an  animal  in  taking  oxygen  from  the  air,  and  replacing 
it  by  carbonic  acid.  There  would,  therefore,  be  no  cause  for  surprise  if, 
in  that  ancient  carbonated  atmosphere,  cryptogamic  plants  alone  could 
maintain  themselves,  and  that  the  flowering  tribes  could  only  appear  after 
a  due  change  in  the  aerial  constitution,  which  also  gave  to  hot-blooded 
animals  the  opportunity  of  coming  forth.  That  change,  as  we  have  said, 
consisted  essentially  in  the  appearance  of  a  great  excess  of  oxygen  gas. 
Such  a  superficial  examination  of  the  question  shows  that  there  is  a  par- 
allelism between  the  physical  conditions  under  which  the  animal  series, 
in  the  lapse  of  countless  centuries,  has  been  placed,  and  those  to  which, 
in  the  shorter  period  of  its  history,  the  developing  individual  is  submit- 
ted, at  least  as  respects  the  respiratory  function.  But  it  is  to  be  re- 
membered that  respiration  is  the  prime  function  in  the  animal  economy. 

As  regards  the  influence  of  heat,  it  has  been  remarked  in  the  preceding 
chapter  that,  at  the  period  of  the  first  appearance  of  organic  influence  of 
forms,  there  was  not  only  a  high,  but  likewise  a  uniform  tern-  heat- 
perature  all  over  the  globe.     The  evidence  establishing  this  is  already 
given ;  but  if  thus,  in  what  might  be  termed  the  infancy  of  the  organic 


504  EPOCHS   OF   DIFFEKENTIATIOX. 

series,  such  a  perfect  uniformity  in  the  condition  of  temperature  obtain- 
ed, the  same  is  often  observed  in  the  first  periods  of  individual  develop- 
ment. The  circumstances  under  which  the  ovum  commences  its  career, 
even  in  the  highest  tribes,  insure  for  it  a  perfect  relief  from  every  varia- 
tion of  heat.  Included  in  the  body  of  the  female,  it  is  cut  off  from  all 
external  causes  of  disturbance,  and  kept  at  the  temperature  of  her  body, 
whatever  that  temperature  may  be.  In  those  cases,  as  in  birds,  in  which 
the  embryo  is  developed  under  circumstances  of  necessary  exposure,  a 
strong  instinct  is  called  into  operation,  and,  by  the  incubation  of  the  pa- 
rent, the  necessary  uniformity  is  secured.  Again,  in  other  instances,  as 
in  the  ova  of  insects,  which,  by  reason  of  their  minuteness  and  their  fre- 
quently exposed  position,  although  they  may  run  through  their  earlier 
changes  with  relatively  great  rapidity,  some  accomplishing  them  in  the 
almost  uniform  warmth  of  a  summer's  day,  development  never  does  nor 
can  occur  until  the  required  condition,  even  if  it  be  temporary,  as  to  uni- 
formity of  temperature,  is  reached. 

These  considerations,  though  not  affording  an  absolute  proof  that  the 
career  of  development  is  guided  by  the  influence  of  external  physical 
conditions,  are  sufficiently  significant  to  cast  an  air  of  probability  over 
that  doctrine ;  and  even  if  we  adopt  the  view  that  the  developing  germ 
possesses  a  plastic  power,  which  spontaneously  compels  it  to  run  forward 
from  stage  to  stage  in  a  predestined  career — if  we  recall  what  has  already- 
been  said  respecting  that  plastic  power,  that  perhaps  it  is  itself  nothing 
more  than  a  manifestation  of  the  remains  of  antecedent  physical  impres- 
sions, we  are  really  brought  back  to  the  same  starting-point ;  and,  under 
any  hypothesis,  we  encounter,  sooner  or  later,  as  a  necessary  postulate, 
the  grand  doctrine  that,  directly  or  indirectly,  development  is  a  function 
of  external  physical  condition. 

It  is  not  to  be  supposed  that  differentiation  takes  place  with  equal 
Epochs  of  dif-  ease  at  aH  periods  of  the  history  of  organic  forms,  whether 
ferentiation.  we  consider  them  in  the  great  scale,  as  constituting  the  ani- 
mal series,  or*  on  the  small,  in  the  individual.  There  are  undoubtedly 
epochs  in  each  of  their  histories  at  which  the  exertion  of  an  external  in- 
fluence will  produce  an  effect  infinitely  greater  than  that  which  would 
occur  at  any  other  moment.  If  we  may  be  permitted  to  use  such  a  me- 
chanical illustration,  the  career  of  an  organism  recalls  the  flight  of  a 
heavy  projectile,  as  a  shell,  thrown  upward,  which,  at  the  first  moments 
of  its  ascent  and  the  last  of  its  descent,  pursues  its  way  irresistibly,  but 
when  it  is  at  the  top  of  its  flight,  and  the  momentum  which  had  been  im- 
parted to  it  is  just  ceasing,  the  slightest  breath  of  air,  or  the  exertion  of 
any  other  insignificant  force,  will  divert  it  into  a  path  different  from  that 
in  which  it  would  have  gone ;  and  so,  in  the  career  of  an  organism,  there 
are  moments  when  forces,  which,  at  another  time,  would  have  been  unfelt, 


REPRODUCTION  AND  DEVELOPMENT.  505 

can  bring  on  differentiation,  and,  through  it,  call  into  existence  new  func- 
tions, and  thereby  forever  determine  a  new  course,  through  which  it  must 
pass.  It  is  because  a  due  weight  has  not  been  given  to  this  considera- 
tion that  many  physiologists  have  depreciated  the  influence  of  external 
circumstances,  or  even  denied  it  altogether,  for  they  have  assumed  that, 
since  we  can  not  produce  a  more  marked  change  than  we  do  in  the  way 
of  accomplishing  a  variation  in  species  by  artificially  altering  the  condi- 
tions under  which  they  exist,  such  conditions  can  have  had  but  little 
power  in  bringing  them  to  their  present  state. 

Upon  the  whole,  there  can  be  no  doubt  that  differentiation  will  occur 
in  a  more  marked  manner  according  as  the  exciting  impres-  Organic  chan- 
sion  is  made  at  an  earlier  period  of  the  organic  career.  Con-  S^^/finft 
versely,  the  more  advanced  the  organism,  the  less  the  prob-  periods  of  life, 
ability  of  differentiation.  For  this  reason  it  is  that  striking  changes  of 
this  kind  are  rarely  witnessed  in  individual  life :  they  occur  chiefly  in 
the  first  embryonic  states,  and  therefore,  for  the  most  part,  require  for 
their  full  manifestation  generation  after  generation.  Great  organic  varia- 
tions are  not,  then,  to  be  expected  in  the  individual,  though  they  may  be 
distinctly  manifested  in  the  course  of  time  by  the  race  to  which  it  be- 
longs. 


CHAPTER  IV. 

OF  REPRODUCTION  AND  DEVELOPMENT. 

Relation  of  Organic  Beings :  they  come  from  a  similar  Cell  and  develop  to  different  Points. — 
Their  Division  by  Classification  is  fictitious.-— Development  and  Differentiation. — Homogenesis 
and  Heterogenesis. — They  depend  on  physical  Conditions. — The  reproductive  State  closes  De- 
velopment. 

Development  is  from  the  General  to  the  Special. — Law  of  Von  Bar. — Invariable  Sequence  in 


OF  REPRODUCTION:  1st.  By  Generation. —  Conjugation  and  Filaments. —  The  Sperm-cell:  its 

Production. — Spermatozoa. —  The  Germ-cell:  its  Production. 
Ovum  in  the  Ovary. — Its  Structure. —  Corpus  Luteum. 

Ovum  in  the  Oviduct. — Mulberry  Mass. — Germinal  Membrane. —  The  CJiorion. 
Ovum  in  the  Uterus. — Membrana  Decidua. — Placenta. — Development  of  the  Embryo. —  Types 

of  Nutrition. — Of  Conception. — Of  Gestation. — Of  Parturition. — Influence  of  both  Parents. 
2d.  By  Gemmation. — Budding  of  Plants  and  Animals. —  Of  Grafting. — Limit  of  Gemmation. — 

Influence  of  Temperature  on  Gemmation. 
Alternations  of  Generation. — Its  Explanation. 

IN  the  popular  view  of  the  organic  world,  each  individual  being  is  re- 
garded as  maintaining  an  existence  independent  and  irre-  Popular  view 
spective  of  all  others,  or,  at  most,  only  connected  with  those  pJSenSXfo*. 
of  its  own  race  or  kind.     Without  any  apparent  disturb-  ganic  beings. 


506  THE   PRIMORDIAL  GERM. 

ance  of  the  general  system,  this  or  that  species  or  genus  might  never 
have  existed,  since  it  stands  in  no  relation  as  being  the  product  of  others, 
nor  as  having  been  concerned  in  giving  origin  to  others. 

But  these  superficial  conceptions  are  now  to  .be  replaced  by  others  of 

a  far  more  general  and  philosophical  order,  which  present  to  us 

organic  creation  under  an  aspect  of  sublime  grandeur,  each  class 

of  beings  standing  in  an  intercommunication  or  connection  with  others — 

a  part  of  a  plan,  the  manifestations  of  which  are  not  limited  to  the  forms 

now  existing,  but  also  include  those  presented  by  the  ancient  geological 

times.     These  views  cast  a  flood  of  light  not  only  upon  the  relations  of 

the  various  races  of  life  to  one  another,  but  also  of  the  human  family  to 

them,  illustrating  the  course  through  which  man  has  hitherto  passed,  and 

indicating  that  through  which,  in  future  ages,  he  is  to  go. 

Starting  from  a  solitary  cell,  development  takes  place,  and,  according 
All  organic  be-  as  extraneous  forces  may  be  brought  into  action,  variable  in 
thf\ametferm  tne^r  nature,  and  differing  in  their  intensity,  the  resulting  or- 
or  cell.  ganisms  will  differ.  If  such  language  may  be  used,  the  aim 

of  Nature  is  to  reach  a  certain  ideal  model  or  archetype.  As  the  pas- 
sage toward  this  ideal  model  is  more  or  less  perfectly  accomplished,  form 
after  form,  in  varied  succession,  arises.  The  original  substratum  or  ma- 
terial is  in  every  instance  alike ;  for  it  matters  not  what  may  be  the  class 
of  animals  or  of  plants,  the  primordial  germ,  as  far  as  investigation  has 
gone,  is  in  every  instance  the  same.  The  microscope  shows  no  differ- 
ence, but,  on  the  contrary,  demonstrates  the  identity  of  the  first  cell, 
which,  if  it  passes  but  a  little  way  on  its  forward  course,  ends  in  pre- 
senting the  obscure  cryptogamic  plant,  or,  if  it  runs  forward  toward 
reaching  the  archetype,  ends  in  the  production  of  man.  The  diversity 
of  form  that  is  eventually  presented  depends  then,  not  upon  the  consti- 
tution or  aspect  of  the  primitive  cell,  but  upon  the  influence  of  the  many 
surrounding  agencies  to  which  it  is  exposed.  In  one  instance,  through 
The  primitive  the  interworking  of  these  agencies — perhaps  by  cessation  of 
ward^oTiffer-  one»  or  PernaPs  by  ^s  increased  intensity — development 
ent  points.  comes  up  rapidly  to  a  certain  point,  and  there  stops.  In 
another  case,  through  change  in  the  conditions,  it  runs  to  a  farther  de- 
gree, and  there  stops.  Organic  beings  are,  therefore,  the  materialized 
embodiment  of  what  must  take  place  through  the  action  of  given  forces, 
of  a  given  intensity,  and  under  given  conditions,  on  an  evolving  cell ; 
The  ciassifica-  and,  though  it  may  suit  the  purposes  of  description  to  classify 
Siy  anTfic-  t^iem  *nto  or^ersJ  genera,  species,  or  other  such  subdivisions, 
titious. .  it  must  never  be  forgotten  that  these  are  artificial  fictions, 

and  have  no  real  foundation  in  nature. 

Not  only  is  the  primordial  cell  in  all  instances  the  same,  but  the  first 
stages  of  its  career  are  in  all  instances  identical,  and  this  whether  we 


VALUE  OF  EMBRYONIC  FORMS.  507 

consider  it  in  the  lowest  or  the  highest  cases,  belonging  either  to  the  veg- 
etable or  the  animal  kingdom.  It  is  a  process  of  repetition  or  reproduc- 
tion, cell  arising  from  cell.  And  here  at  once  we  may  correct  the  lan- 
guage so  often  used — indeed,  which  we  have  ourselves  just  used  in  this 
respect,  for  such  terms  as  high  and  low  are  only  to  be  employed  in  a  very 
restricted  sense.  The  evolving  cell  gives  rise  to  other- cells,  but  for  a  pe- 
riod of  time  no  indication  is  presented  as  to  which  of  the  two  kingdoms 
it  is  to  belong,  animal  or  plant.  By  degrees,  as  the  develop-  Development 
ment  goes  on,  that  point  is  determined,  and  so,  one  after  an-  is  attended  by 
other,  the  unfolding  mass  gradually  reveals  the  class,  order,  evolving  of  pe- 
family,  genus,  species,  and,  finally,  its  sex  and  individual  pe-  culiarities- 
culiarities.  In  all  this  there  is  an  evolving  of  the  special  out  of  the  gen- 
eral ;  one  after  another,  peculiarities,  which  are  more  and  more  minute, 
arise ;  and  thus  we  are  not  to  regard  the  progress  of  development  as  tak- 
ing place  from  the  lower  to  the  higher,  forms  that  are  more  and  more  com- 
plex arising  in  succession,  but  we  are  to  regard  it  as  the  gradual  unfold- 
ing of  the  special  from  the  general. 

This  career  of  development  applies  equally  to  the  case  of  any  individ- 
ual animal,  or  any  race  of  animals.  Thus  man  himself,  in  Analogy  of  de- 
succession,  passes  through  a  great  variety  of  forms,  from  the  ^faSSidual 
condition  of  a  simple  cell;  these  forms  merging  by  degrees  andin  the  race, 
into  one  another,  the  form  of  tlie  serpent,  of  the  fish,  of  the  bird,  and  this 
not  only  as  regards  the  entire  system  in  the  aggregate,  but  also  as  re- 
gards each  one  of  its  constituent  mechanisms — the  nervous  system,  the 
circulatory,  the  digestive.  Now,  on  the  passage  onward,  these  forms  are 
to  be  regarded,  as  has  been  well  expressed,  each  one  as  the  scaffolding 
by  which  the  next  is  built ;  and  just  as  man,  in  his  embryonic  transit, 
presents  these  successive  aspects  on  the  small  scale,  so  does  the  entire 
animal  series  present  them  in  the  world  on  the  great  scale.  Kaces  of 
animals  are  not  to  be  compared  as  though  they  were  more  perfect  or  low- 
er than  one  another,  but  as  having  advanced  more  or  less  in  the  direction 
from  the  general  to  the  special ;  and  therefore,  in  this  philosophical  view, 
we  are  justified  in  regarding  those  animated  forms  which  heretofore  have 
been  spoken  of  as  lower  in  the  animal  scale  as  being,  in  reality,  the  em- 
bryos of  those  that  are  higher ;  and  this  should  lead  us  to  a  juster  esti- 
mate of  their  relation  of  value  toward  one  another,  since  we  are  very  apt 
to  contrast  them  in  that  respect.  In  the  case  of  an  individ-  Value  of  em- 
ual,  as  in  man,  we  put  at  once  a  true  interpretation  on  the  kryonic  forms, 
value  of  the  various  transitory  conditions  through  which  he  has  passed, 
estimating  these  as  of  but  little  intrinsic  importance;  as  being,  as  it  were, 
no  more  than  links  in  a  chain ;  and  this  may  teach  us  a  more  just  appre- 
ciation of  the  relations  of  animal  races  to  one  another  and  to  the  human 
species.  It  may  teach  us  the  folly  of  comparing,  as  some  have  endeav- 


508  DEVELOPMENT   OF   THE   SPECIAL   FROM   THE   GENERAL. 

ored  to  do,  the  animal  tribes  with  ourselves  ;  of  measuring  their  instincts 
with  our  mental  operations ;  things  which  are  different  terms  of  two  dif- 
ferent series,  and  things  which  are  incommensurable. 

There  are  three  cases  in  which  we  might  consider  this  career.  These 
are,  first,  in  the  development  of  particular  organs,  as  the  digestive,  res- 
piratory, or  circulatory ;  second,  in  the  development  of  individual  beings, 
which  pass  in  their  onward  progress,  as  we  have  said,  through  various 
forms  in  succession;  third,  in  the  development  of  species,  presenting 
what  have  been  formerly  designated  as  successive  stages  of  increasing 
perfection.  For  all  these  various  cases  a  single  illustration  may  suffice, 
illustration  of  Thus,  in  the  primitive  period  of  life,  a  single  membrane  dis- 
the  unfolding  charges  promiscuously  and  contemporaneously  all  the  va- 

of  the  special  °        f     .      f        ,.  .,     -,.        .       ..  .          . 

from  the  gen-  nous  organic  functions — it  digests,  it  respires,  it  secretes ; 
eral-  but,  a  little  .advance  onward,  special  portions  of  it  are  allot- 

ted for  one  and  another  of  these  uses,  and  a  localization,  a  centralization 
of  function  ensues,  and  things  that  were  mixed  in  confusion  become  sep- 
arate and  distinct.  As  the  passage  onward  is  made,  still  farther  special- 
izations are  introduced,  and  so  on  in  succession.  Thus  at  the  two  ex- 
tremes we  may  contemplate  the  single  germinal  membrane  of  the  ovum, 
which  is  discharging  contemporaneously  every  function — digesting,  ab- 
sorbing, respiring,  etc. — and  the  complete  organic  apparatus  of  man,  the 
stQmach,  the  lungs,  the  skin,  the  kidneys,  and  the  liver — mechanisms 
set  apart  each  for  the  discharge  of  a  special  duty,  yet  each  having  arisen, 
as  we  know  positively  from  watching  their  order  of  development,  from 
that  simple  germinal  membrane.  We  must  not,  therefore,  permit  our- 
selves to  be  deceived  by  the  appearance  of  complexity  they  exhibit, 
since,  intricate  as  may  be  their  construction,  they  have  all  arisen  through 
gradual  centralization,  one  duty  being  separated  from  another,  and  hav- 
ing an  appropriate  mechanism  for  itself;  and  so,  at  last,  it  comes  to  pass 
that  even  the  minutest  conditions  are  discharged  by  a  special  part. 
Thus,  in  the  kidney,  the  salts  are  removed  by  one  portion  of  the  struc- 
ture and  the  organic  constituents  by  another ;  yet,  even  in  these  ut- 
most conditions  of  refinement,  the  primitive  condition  is  at  all  times 
ready  to  be  reproduced,  and,  when  driven  to  it,  each  of  these  structures 
can  act  vicariously  for  the  others,  and  discharge  for  the  others  their 
duty. 

It  is  unnecessary  for  our  purpose  to  multiply  instances,  since  every 
page  of  natural  history,  comparative  anatomy,  and  embryology  presents 
them  in  abundance ;  but  it  may  be  to  the  purpose  to  remark  that  this 
doctrine  leads  to  more  worthy  conceptions  of  the  system  of  nature ; 
for  if  we  suppose  that  there  has  been,  in  the  case  of  the  animal  series, 
a  passage  from  things  that  are  less  perfect  to  things  that  are  more  so, 
though  this  may  be  agreeable  to  our  own  experience,  which  is  essen- 


ILLUSTRATIONS   OF   DEVELOPMENT.  509 

tially  tentative,  it  gives  us  very  base  notions  of  the  manner  Base  nature  of 
in  which  natural  operations  are  conducted,  since  we  can  not  ^ew  oniw  or- 
divest  ourselves  of  the  idea  that  such  a  passage  from  imper-  ganic  world. 
fection  to  perfection  implies  trial,  verification,  and  improvement :  a  pro- 
cess which,  though  it  is  suited  to  the  limited  knowledge  of  man,  is  not 
in  accordance  with  the  precision,  perfection,  and  energy  of  Nature,  and  is 
to  "be  rejected  the  moment  we  consider  that  we  deal  with  the  acts  of 
Omniscience  and  Omnipotence.  Moreover,  that  erroneous  view  leads  to 
fallacious  estimates,  both  in  the  animal  series  and  in  the  individual,  of 
the  character  of  transitory  forms,  conferring  on  them  too  much  inde- 
pendence, and  therefore  too  much  dignity;  for  the  transitory  forms  of 
embryonic  life  and  the  forms  of  animal  species  are  the  equivalents  of 
each  other. 

Every  living  being,  therefore,  springs  from  a  germ,  which  will  develop 
itself  into  the  likeness  of  its  parent,  provided  it  is  submit-  career  and  stop- 
ted  to  the  same  conditions  through  which,  its  parent  pass-  Pase  of  a  devel- 
ed ;  but  if  the  conditions  be  changed,  it  will  either  take  pends  on  exter- 
on  a  new  aspect,  or  if  they  have  become  incompatible,  it  nal  condltlons- 
will  cease  to  exist.  Similarity  of  development  depends  on  similarity  of 
condition,  as  is  abundantly  proved  by  such  instances  as  the  almost  per- 
fect resemblance  of  the  two  sides  of  the  body,  which,  in  reality,  may  be 
regarded  as  distinct  individual  forms.  To  the  proof  thus  derived  from 
bilateral  symmetiy  as  occurring  in  man  might  be  added  such  suggestions 
as  arise  from  the  well-known  resemblance  of  twins ;  and  as  identity  of 
condition  will  thus  give  origin  to  analogy  of  development,  so  we  may 
fairly  infer  that  difference  of  condition,  no  matter  in  what  respect  the  dif- 
ference may  be,  will  give  rise  to  difference  of  structure ;  thus  experienced 
gardeners  have  shown  that  the  sex  of  flowers  is,  to  a  very  great  extent, 
determined  by  the  brilliancy  of  the  light  in  which  they  grow.  Differ- 
ence in  the  supply  of  nutritive  material  removes  the  spines  from  one 
plant,  or  doubles  the  flowers  of  another,  by  changing  its  stamens .  into 
petals,  or  alters  the  cycle  of  career,  and  makes  annuals  into  biennials. 
As  illustrations  of  the  complete  changes  of  form  during  development, 
241.  the  three  following  cases  may  be 

presented :  in  Fig.  241  are  shown 
the  ova  of  the  frog,  which  are  trans- 
parent  spherical  bodies,  containing 
a  dark  globule.  From  this,  by  de- 
velopment, the  tadpole,  which  is  a 
true  fish,  breathing  by  gills,  arises. 

Development  of  the  frog.  The  figures  represent  a  side  and 

upper  view.     After  growth  has  taken  place  to  a  certain  degree,  a  change 
of  structure  becomes  apparent,  limbs  gradually  emerging,  and  the  ani- 


510 


ILLUSTRATIONS   OF   DEVELOPMENT. 


Fig-  242,  mal,  after  passing  through  an  inter- 

mediate state,  eventually  loses  its 
gills  and  tail,  ceases  its  aquatic,  and 
commences  aerial  respiration,  and 
shows  the  aspect,  Fig.  242,  of  the 
perfect  frog. 

Fig.  243  represents  the  success- 
ive metamorphoses  of  the  Carcinus 
mamas,  or  edible  crab,  as  given  by  Mr.  Couch.     A  represents  the  animal 


Fig.  243. 


Development  of  the  crab. 

on  its  emergence  from  the  egg.  It  has  a  hemispherical  shield  on  the 
head  and  thorax,  with  a  projecting  spine,  a  tail  formed  of  six  segments, 
the  two  last  being  joined  laterally.  The  second  form,  at  B,  exhibits  a 
great  change:  the  spine  has  disappeared,  the  shield  is  depressed,  the 
eyes  on  footstalks ;  there  are  claws,  and  the  tail  is  often  carried  bent 
under  the  body.  When  this  shell,  like  its  predecessor,  has  been  cast, 
the  third  form,  C,  is  assumed,  the  transition  adapting  the  animal  for 
walking  rather  than  swimming.  The  final  form,  D,  is  taken  on  at  the 
next  moult,  and  now  development  ceases,  and  growth  only  takes  place. 
Fig.  244  illustrates  the  metamorphoses  of  a  lepidopterous  insect,  the 

Bombyx  mori,  or  moth 
of  the  silk- worm.  From 
the  eggs  there  arises  a 
caterpillar,  which  not  on- 
ly possesses  the  means  of 
locomotion  by  feet,  etc., 
but  also  contains  within 
it  the  rudiments  of  the 
organs  to  be  eventually 
assumed.  In  this  state 

Development  of  insects.  the  insect  passes  under 

the  name  of  a  larva,  because  it  is  covered  with  a  series  of  teguments, 


GROWTH,    DIFFERENTIATION,    DEVELOPMENT.  511 

which,  like  masks,  conceal  the  interior  structure.     These,  in  succession, 
are  cast  off. 

After  many  such  successive  castings  of  the  skin,  the  insect  enters  into 
the  pupa  or  chrysalis  state.  It  has  no  organs  of  locomotion,  and,  as  it 
has  been,  with  some  degree  of  imagination,  said,  becomes  an  egg  again. 
After  resting  in  this  state  for  a  certain  time,  it  bursts  its  confinement, 
and  assumes  the  form  of  an  aerial,  swift-moving  winged  insect.  This  is 
its  imago  state.  • 

It  will  now  be  convenient  to  give  a  more  precise  definition  to  terms 
which  have  been  hitherto  used  with  a  certain  latitude. 

By  the  term  growth  is  to  be  understood  the  increase  in  size  of  a  struc- 
ture, without  its  assuming  any  variation  as  respects  the  na-  Definition  of 
ture  of  its  fabric  or  of  the  functions  it  discharges.  SS^  and 

By  differentiation  is  meant  an  increase  involving  modifica-  development, 
tion  of  fabric  and  the  assumption  of  new  function. 

By  development  is  meant  a  differentiation  of  a  higher  order,  or  com- 
pound differentiation.  Usually  it  implies  growth  and  differentiation  con- 
jointly. 

As  illustrations  of  the  preceding  definitions,  it  may  be  said  that  a  crys- 
tal grows,  its  enlargement  presenting  no  structural  variation  and  no  new 
quality.  Cells  differentiate  from  their  normal  spherical  form,  and,  assum- 
ing a  cylindroid  figure,  give  origin  to  vascular  tissue,  the  vessels  so  aris- 
ing serving  for  new  purposes,  as  for  the  conveyance  of  gases  or  liquids. 
A  seed  develops,  for  the  organism  to  which  it  gives  rise  not  only  offers 
continually  increasing  dimensions,  but  at  all  points  the  origination  of 
novel  structures,  arising  by  differentiation  from  adjacent  and  pre-existing 
ones,  these  new  structures  having  also  new  functions. 

By  homogenesis  is  meant  the  production  of  an  organism  in  all  respects 
like  its  parent ;  by  heterogenesis,  the  production  of  an  or-  Homoo.enesis 
ganism  unlike  its  parent.  «     and  heterogen- 

For  the  sake  of  brevity  and  simplicity,  we  may  suppose  esis' 
that  there  resides  in  every  germ,  and,  therefore,  in  every  organism,  a  prin- 
ciple or  quality  which  governs  the  collocation  or  grouping  of  new  parts, 
the  same  to  which  allusion  has  heretofore  been  made  under  the  designa- 
tion of  plastic  power.  It  is  unnecessary  for  us  here  to  burden  our  con- 
ceptions of  such  a  power  with  any  hypotheses  respecting  its  nature,  it 
being  understood  that  we  use  the  title  of  this  supposed  agent  only  as  an 
expression  of  convenience. 

The  production  of  every  organism  appears,  as  far  as  existing  observa- 
tions and  experiments  go,  to  be  referable  to  a  previously  ex-  An  organ,-c 
isting  organism.     This  being  admitted,  generation  and  repro-  molecule  the 
duction  imply,  as  their  starting-point,  an  organic  molecule.  pou 
Such  a  combination,  furnished  with  nutrition,  grows,  its  plastic  power 


512  HOMOGENESIS   AND   HETEKOGENESIS. 

grouping  the  new  material.  But  such  a  growth  can  not  take  place  to  any 
extent  without  a  variation  being  encountered  in  the  surrounding  condi- 
tions, and  the  instant  that  this  occurs,  differentiation  ensues  as  its  neces- 
sary consequence.  Growth  under  changed  circumstances  is  then  differ- 
entiation. If  the  order  of  variation,  as  regards  condition,  is  exactly  the 
Condition  for  same  m  tne  case  °^  two  growing  and  differentiating  combi- 
simiiarity  of  nations,  their  career  of  development  will  be  exactly  alike,  and 
2nt*  the*  forms  they  will  present  at  the  same  epoch  of  their  course 
will  be  the  same.  According  as  the  career  is  short,  the  probabilities  of 
identity  are  greater,  since  the  chances  of  variation,  which  might  be  en- 
countered in  the  two  cases,  are  less.  But  where  the  career  is  more  pro- 
tracted, and  many  conditions  in  succession  must  be  encountered,  it  can 
not  happen  that  there  will  be  an  exact  resemblance  in  the  course  of  two 
organic  combinations,  and  therefore  there  never  can  be  an  absolute  iden- 
tity in  the  aspect  of  any  two  resulting  forms. 

The  general  result  of  every  development  is  heterogenesis.  No  parent 
Development  organism  ever  reproduces  another  absolutely  like  itself,  un- 
tendTtohete-  ^ess  **  ^e  *n  ^e  ^owest  developed  types,  in  which  the  oppor- 
rogenesis.  tunity  for  change  is  at  a  minimum.  Homogenesis  is  only  ap- 
proached as  the  conditions  bringing  on  differentiation  approach  similari- 
ty; it  therefore  sinks  into  a  special  case  coming  under  a  more  general 
law,  and,  indeed,  speaking  with  exactness,  we  might  say  that  in  the  nat- 
ural world  it  never  occurs,  the  prevalent  notion  which  regards  it  as  the 
rule  and  heterogenesis  as  the  exception  being  altogether  illusory.  Ev- 
ery grade  of  organism,  vegetable  and  animal,  furnishes  us  with  examples 
of  this  truth.  Let  us  look  for  a  moment  at  the  highest  tribes ;  and  in 
them  reproduction  never  takes  place  except  by  pairs  of  individuals  of  dif- 
ferent sexes.  Eigorously,  therefore,  the  births  should  also  be  by  pairs  of 
different  sexes.  Moreover,  if  it  be  necessary  in  these  general  and  super- 
ficial considerations,  let  us  direct  our  attention  to  the  special  case  of  man. 
The  infant  necessarily  differs  from  one  of  its  parents  in  sex,  and  from 
both  in  size,  weight,  endowments,  and'  physical  attributes.  It  is  like 
neither  of  them.  The  popular  notion  may  suggest  that  a  closer  resem- 
blance will  be  reached,  perhaps,  after  the  lapse  of  thirty  or  forty  years, 
when  a  nearer  approach  to  the  form  of  one  of  the  parents  may  be  offered 
with  elements  incorporated  from  the  lineaments  of  the  other ;  but  even 
m  this  case  a  rigorous  examination  compels  us  to  admit  that  like  has  not 
produced  like. 

Eeflecting  on  this  popular  illustration  more  profoundly,  we  discern 
Cycles  of  pro-  wherein  the  error  consists.  Instead  of  comparing  cycles  of 
Cared° and00™"  Process»  we  ^ave  ^een  blundering  with  isolated  forms,  which 
individual  arise  at  different  epochs  therein.  Without  going  into  tedi- 
ous details,  man  presents,  as  regards  the  most  important  of 


REPRODUCTIVE   STATE   ENDS    DEVELOPMENT.  513 

his  constituent  structures,  his  nervous  system,  the  successive  character- 
istics of  an  avertebrated  animal,  a  fish,  a  turtle,  a  bird,  a  quadruped,  a 
quadrumanous  animal,  before  he  assumes  the  special  human  character- 
istics. This  is  his  cycle  of  life,  and  it  is  the  same  cycle  in  one  case  as 
in  another. 

But  the  moment  that  our  view  is  thus  enlarged,  we  see  that  it  is  not 
the  individual  with  which  we  should  deal,  for  an  individual  we  can  scarce- 
ly define,  since  he  is  continually  differing  from  himself.  It  is  with  a  cy- 
cle of  proceeding,  or  a  course  of  operations  that  we  are  engaged,  a  series 
of  forms  being  the  outward  manifestation  of  the  succeeding  periods  of 
that  cycle  or  course. 

An  infant,  though  unlike  both  its  parents  in  form,  has  run  through  a 
career  like  that  passed  through  by  them  both.  Sexual  differentiation, 
which  indeed  is  one  of  the  last  differentiations  occurring,  offers  no  excep- 
tion to  the  truth  of  this  remark.  The  similitude  lies  in  the  career,  not 
in  the  form  taken  at  different  epochs. 

The  essential  principle,  then,  is,  not  that  an  organism  produces  a  like 
organism,  but  it  produces  a  germ  which,  being  placed  under  The  reproduct_ 
similar  circumstances,  passes  through  a  like  career  of  devel-  ive  state  closes 
opment,  and  at  successive  periods  offers  an  orderly  series  of 
forms.  The  career  is  commonly  observed  to  close  as  soon  as  the  capac- 
ity for  reproduction  is  assumed.  Hence,  in  every  organism,  the  assump- 
tion of  the  reproductive  state  is  the  signal  that  the  end  of  development 
is  at  hand. 

It  does  not  plainly  appear  what  are  the  circumstances  which  give  rise 
to  the  assumption  of  this  capacity ;  nevertheless,  it  may  take  place  at 
any  moment  of  the  career.  In  the  Volvox  globator  it  occurs  almost  at 
the  close  of  the  first  stage,  for  the  germ  only  reaches  the  condition  de- 
scribed hereafter  as  the  mulberry  mass  when  it  becomes  capable  of  re- 
production ;  but  in  man  the  developing  organism  has  a  long  journey  to 
perform  beyond  this  first  step.  Except  in  the  condition  here  dwelt  upon, 
he  differs  in  no  respect  from  his  humbler  comrade  at  this  point.  The 
tendency  to  a  gliding  off  into  the  reproductive  phase  is  in  him  repressed, 
and  therefore  differentiation  and  development  continue  to  go  on. 

During  the  development  of  any  new  organism,  the  new  parts  uniformly 
arise  from  the  old  ones  ;  they  are  not  built  from  foreign  mate-  All  the  parts  of 
rials  depositing  themselves  upon  new  centres,  but  are  educed  an.  organism 
by  the  unfolding,  enlarging,  and  modeling  of  parts  already 


common  cen- 


existing.     An  organism  is  not  developed  as  we  enlarge  a  tral  origin- 
house,  by  building  part  to  part,  but  it  all  expands  from  one  common  or 
single  centre.     As  the  sphere  of  its  expansion  becomes  greater,  the  op- 
portunity arises  for  devoting  different  regions  to  different  uses,  and  thus 
offices  which  were  confusedly  intermingled  become  separated  out,  and, 

KK 


514  LAW   OF   VON   BAR. 

as,  in  social  undertakings,  the  division  of  labor  gives  greater  perfection  to 
the  work,  so  in  this,  functions  which,  because  they  were  blended,  were 
imperfectly  discharged,  now  assume  precision  and  power,  because  they 
are  disentangled  from  what  were  perhaps  countervailing  conditions. 
By  these  considerations,  we  are  gradually  led  to  the  general  law  of  de- 
velopment, first  recognized  by  Yon  Bar,  and  passing  under 

LawofVonBar.  r  rrn  •      •  J  •        ?  •        i 

his  name.  This  is  somewhat  obscurely  enunciated  in  the 
following  terms :  "  The  heterogeneous  arises  from  the  homogeneous  by  a 
gradual  process  of  change."  By  this  it  is  meant  that,  in  the  process  of 
development,  the  stages  are  not  from  forms  that  are  of  a  degraded  to  those 
of  a  higher  type,  but  that  from  the  general  the  special,  which  was  therein 
included,  is  gradually  evolved. 

In  conclusion  of  these  preliminary  remarks  on  reproduction,  it  may  be 
Invariable  se-  ^served  that,  even  in  the  highest  and  most  elaborate  types, 
quence  and  dif-  the  causes  which  bring  on  differentiation  follow  each  other  in 
such  a  predetermined  sequence,  that  the  whole  phenomenon 
might  be  said  to  be  under  the  dominion  of  mathematical  conditions.  As 
a  striking  instance  of  this  may  be  mentioned,  in  the  case  of  man,  the  nu- 
merical equality  of  the  sexes  ;  and  that  this  singular  result  is  determined 
by  the  alternate  preponderance  of  conditions  which  are  otherwise  nicely 
balanced,  is  shown  by  the  interesting  instances  occurring  among  insects 
of  dimidiate  and  quadrate  hermaphroditism,  in  .the  former  of  which 
the  resulting  insect  is  of  different  sexes  on  the  .two  sides  of  its  body, 
and  in  the  latter  the  male  and  female  portions  are  quadrantally  arranged. 
If  the  left  side  of  the  head  and  thorax  are  those  of  a  male-  insect,  the 
right  half  of  the  abdomen  is  of  the  same  kind,  the  intervening  portions 
being  of  the  other  sex.  The  neuter  state  might  even  be  imagined  to 
arise  from  the  more  precise  blending,  balancing,  and  confusing  of  such 
conditions  as  here  give  evidence  of  an  incipient  tendency  to  separate  from 
one  another. 

In  the  farther  discussion  of  reproduction  we  shall  find  it  conveniently 
Divisions  of  considered  under  two  distinct  divisions;  first,  generation; 
reproduction.  secon<3?  gemmation.  Our  attention  may,  then,  be  profitably 
directed  to  the  singular  facts  known  under  the  designation  of  alternation 
of  generations.  As  illustrations  of  the  terms  here  employed,  it  may  be 
stated  that  the  production  of  a  seed  and  the  development  of  a  plant  there- 
from are  to  be  considered  in  connection  with  generation,  and  that  the  ob- 
taining of  new  plants  and  trees  by  budding  and  grafting,  and  the  pro- 
duction of  many  new  hydras  by  their  sprouting  forth  from  an  old  one, 
are  to  be  considered  under  gemmation.  By  the  alternation  of  genera- 
tions is  meant  that  an  organism,  A,  will  give  rise  to  a  second  one,  B, 
wholly  unlike  itself,  and  that  this  second  organism,  B,  will  give  rise  to  a 
third,  C,  unlike  itself,  but  C  shall  resemble  A.  This  singular  condition 


GENERATION. 


515 


of  things  will  be  shown  to  originate  in  the  periodical  alternation  of  gen- 
eration and  gemmation  respectively. 

1ST.    OP   GENERATION. 

Eeproduction  by  generation  is  accomplished  on  two  different  types : 
1st.  By  the  conjugation  of  two  similar  cells ;  2d.  By  filaments. 

In  the  first,  that  is,  by  the  conjugation  of  two  similar  cells,  a  third 
body,  called  a  sporangium,  results.  Of  this  process  there  Three  modifi 
appear  to  be  three  different  modifications :  1st.  The  two  sim-  cations  of  con- 
ilar  conjugating  cells  discharge  their  endochrome,  or  coloring  Jusatlon- 
material,  each  voiding  itself  completely,  and  the  sporangium  arises  from 
the  mixture ;  2d.  A  dilatation  forms  on  the  point  of  union  of  the  two 
conjugating  cells,  and  into  this  dilatation  the  endochromes  of  both  cells 
are  passed ;  3d.  The  endochrome  of  one  cell  is  wholly  retained,  and  that 
of  the  other  is  added  to  it,  the  one  becoming  void,  and  in  the  other  the 
sporangium  being  produced.  This,  occurring  in  the  lowest  vegetables, 
among  which  it  was  for  a  long  time  supposed  that  the  type  of  reproduc- 
tion is  totally  different  from  that  of  flowering  plants  and  animals,  pre- 
sents us  with  the  first  traces  of  what  is  eventually  displayed  as  differ- 
ence of  sex. 

This  shadowing  forth  of  the  difference  of  sexes  is  illustrated  in  a  very 
instructive  manner  by  the  Zygnema  quininum,  a  fresh-water  conferva. 
Its  manner  of  growth  is  what  has  been  already  described  in  the  case  of 
the  Conferva  glomerata,  Fig.  231.  In  the  annexed  Fig.  245  is  repre- 


. Development  and  reproduction  of  Zygnema  quininum. 

sented  at  A  the  process  of  growth  by  the  subdivision  of  cells,  a  b  c  repre- 
senting three  such  cells,  the  middle  one,  5,  being  in  the  act  of  subdivision. 
At  B  two  threads  are  in  the  act  of  conjugation.  The  endochromes  of 
both  are  spirally  arranged,  and  dilatations  reaching  from  one  to  the  other 
are  here  and  there  seen.  At  C  the  endochromes  of  one  thread,  <z,  have 
wholly  passed  over  to  the  other  thread,  b,  and  the  round  bodies,  or  spo- 


516  SPERM-CELLS. 

rangia,  are  the  result.  It  is  this  passage  from  one  thread  to  the  other 
which  betrays  the  first  indications  of  sex. 

In  the  second,  that  is,  by  filaments,  two  cells  are  again  necessary, 
which,  differing  in  construction  and  also  in  function,  are  des- 
tionsbyfiia-  ignated  the  sperm-cell  and  germ-cell  respectively.  Of  this 
ments.  ^^Q  there  are  two  modifications :  1st.  Reproduction  by  mov- 

ing filaments,  as  presented  in  the  higher  algse  and  ferns ;  2d.  By  elon- 
gating filaments,  as  in  flowering  plants.  The  moving  filaments,  which 
were  discovered  in  the  case  of  animals  soon  after  the  introduction  of  the 
microscope,  were  regarded  as  animalcules,  and  passed  under  the  designa- 
tion of  spermatozoa.  The  germ  which  arises  in  the  first  of  these  modi- 
fications is,  in  the  lower  tribes,  unprovided  with  any  nutritive  supply ; 
in  the  higher,  a  stock  of  food  is  prepared  for  it  by  the  parent.  In.  the 
second,  the  sperm-cell,  or,  as  it  is  frequently  termed,  pollen  grain,  does 
not  produce  a  moving  filament,  but  elongates  itself  into  a  delicate  tube 
until  it  reaches  the  germ-cell.  A  stock  of  nutritious  matter  is  placed 
around  the  resulting  embryo,  and  this  is  the  ordinary  construction  of 
seeds. 

Eestricting  our  description  to  the  case  which  more  immediately  inter- 
ests us,  we  shall  first  consider  the  mode  of  origin  and  nature  of  the 
sperm-cell  and  its  filaments  in  animals,  and  then  of  the  germ-cell  and  its 
process  of  development  when  fertilized. 

1st.  Of  the  Sperm-cell. — The  testes  are  the  organs  in  which  the 
sperm-cells  and  filaments  arise  in  man.  They  are  of  an  ovoid  fbrm ; 
each  is  covered  with  a  white  envelope,  the  tunica  albuginea.  A  serous 
membrane,  folded  as  a  shut  sac,  overlies  this  tunic.  From  the  inner 
surface  a  number  of  delicate  projections  arise,  which  divide  the  organ  into 
several  compartments.  In  these  compartments  are  lodged  lobules  aris- 
ing from  the  tubuli  seminiferi  and  their  supplying  blood-vessels.  There 
Production  of  are  a^out  450  lobules  in  each  testis  ;  their  shape  is  conical, 
sperm-ceils  by  the  diameter  of  the  tubes  of  which  they  are  composed  about 
the  2-^0-  of  an  inch.  The  total  length  of  this  tubular  struc- 
ture is  about  three  quarters  of  a  mile.  Before  the  tubuli  of  each  lobule 
reach  the  rete  testis,  they  cease  to  be  convoluted,  and  bundles  of  them, 
uniting  into  larger  vessels,  are  designated  tubuli  recti.  In  the  rete  tes- 
tis there  are  from  half  a  dozen  to  a  dozen  of  these  tubes,  which  various- 
ly anastomose  with  one  another  and  divide.  They  empty  into  the  vasa 
efferentia,  which,  from  being  straight,  become  convoluted,  a  series  of 
cones  arising,  which  together  form  the  globus  major  of  the  epididymis. 
This  is  a  convoluted  canal,  of  about  twenty  feet  in  length,  which,  de- 
scending, receives  beyond  its  globus  minor  the  vasculum  aberrans.  It 
then  empties  into  the  vas  deferens. 

Fig.  246,  human  testis :  «,  testis ;  £,  lobes ;  <?,  tubuli  recti ;  d,  rete 


THE   TESTIS. 


517 


Fig.  246. 


The  testis. 


vasculosum  ;  e,  vasa  efferentia ;  y, 
coni  vasculosi ;  <7,  epididymis  ;  A, 
vas  deferens ;  i,  vas  aberrans ;  ?ft, 
branches  of  the  spermatica  inter- 
na  of  the  testis  and  epididymis ; 
w,  ramification  on  the  testis  ;  0,  ar- 
teria  deferentialis ;  p,  anastomosis 
with  a  branch  of  the  spermatic. 
(Arnold.) 

The  secretion  of  the  testis  must 
be  taken  for  examination  from  the 
vas  defe'rens  or  epididymis,  before 
it  has  been  mixed  with  the  fluid  of 
the  prostate  and  Cowper's  glands, 
or  with  mucus.  It  may  be  min- 
gled with  a  little  albumen  or  se- 
rum for  the  purpose  of  dilution,  and, 
when  examined  with  a  power  of 
500  diameters,  exhibits  multitudes 
of  moving  bodies.  These  are  the 
seminal  animalcules,  or  spermato- 
zoa. Among  them  are  to  be  seen,  here  and  there,  round  granular  bod- 
ies, the  seminal  granules.  These,  with  the  spermatozoa,  are  sustained 
in  a  clear  and  transparent  liquid.  The  examination  of  these  different 
constituents  is  conducted  with  difficulty,  since  they  can  not  be  separated 
from  one  another  by  means  of  filtration.  The  spermatozoa  arise  from 
the  seminal  granules. 

The  spermatozoa  are  found  in  the  spermatic  fluid  of  all  animals  after 
puberty,  their  form  being  different  in  different  classes  and  spermatozoa, 
species.  Generally  they  may  be  described'  as  consisting  of  description  of. 
a  little  oval-shaped  head,  from  which  a  delicate  filament  or  tail  projects. 
The  motion  of  the  spermatozoa  is  accomplished  by  means  of  their  fil- 
ament. It  takes  place  in  different  ways,  sometimes  the  filament  vibrat- 
ing like  a  whip,  sometimes  rotating  like  a  screw,  and  sometimes  a  spin- 
ning round,  as  it  were,  upon  a  pivot,  occurs,  the  filament  having  been 
coiled  like  a  watch-spring.  The  rate  of  motion  seems  under  the  micro- 
scope to  be  rapid ;  it  is,  however,  estimated  at  an  inch  in  thirteen  min- 
utes. In  man,  their  entire  length  may  be  estimated  at  about  the  -g-L  of 
an  inch,  the  length  of  the  head  being  about  the  3^^,  and  its  Human  sper- 
breadth  the  Iojj00.  They  continue  to  exhibit  motion  in  matozoa- 
birds  for  fifteen  or  twenty  minutes  after  death ;  in  cold-blooded  animals 
even  after  days.  They  withstand,  for  a  time,  the  action  of  solutions  of 
sugar  and  salt,  but  are  destroyed  at  once  by  alcohol  and  dilute  acids, 


518  SPEKMATOZOA. 

which  appear  to  affect  their  organization.  Strychnia,  opium,  and  hy- 
drocyanic acid  likewise  stop  their  motions,  but  without  causing  any 
change  in  their  form. 

The  production  of  spermatozoa  is  best  studied  in  the  case  of  birds. 
Spermatozoa  For  this  purpose  Wagner  recommends  that  one  of  the  order 
in  birds.  of  Passeres  be  taken  in  the  pairing  time.  The  condition  of 
the  testes  indicates  the  state  of  evolution  of  the  spermatozoa.  In  win- 
ter those  organs  are  of  the  size  of  a  pin's  head,  but  in  spring  they  have 
increased  twenty  or  thirty  fold.  Exteriorly  they  exhibit  convolutions  like 
those  of  the  brain,  and  contain  granules  and  seminal  globules.  After 
pairing  time  is  over,  they  relapse  to  their  original  diminutive  state.  The 
seminal  globules  appear  to  be  derived  from  the  epithelial  cells  lining  the 
tubuli  seminiferi.  They  are  developed  into  what  are  termed  primary 
cells,  each  of  which  contains  a  number  of  secondary  cells  or  vesicles  of 
evolution.  In  the  interior  of  these  vesicles  the  spermatozoa  originate, 
as  a  derivation  or  development  from  the  nucleus,  each  vesicle  giving  rise 
Evolution  of  to  one  spermatozoon.  When  this  has  reached  perfection,  the 
spermatozoa,  vesicle  deliquesces  and  sets  it  free.  There  are  from  one  to 
twenty  vesicles  of  evolution  in  each  primary  cell.  In  birds  the  filaments 
may  be  retained  for  a  length  of  time  in  the  primary  cell  after  deliquescence 
of  the  vesicle,  but  in  mammals,  as  soon  as  the  filament  is  mature  it  es- 
capes. In  the  former  case  the  filaments  aggregate  into  bundles,  but  they 
break  up  into  individuals  when  the  primary  cell  deliquesces. 

24L  Fig.  247,  spermatozoic  filaments,  develop- 

ing in  Certhea  vulgaris :  #,  seminal  granule ; 
£,  cyst,  with  two  vesicles  of  evolution,  many 
granules,  and  a  bundle  of  spermatozoa ;  £,  oval 
cyst,  with  spermatozoa  coiled  up.  (Wagner. ) 
Of  the  formation  of  spermatic  filaments 
Dr.  Burnett  gives  an  account  somewhat  dif- 
ferent from  the  preceding.  According  to  him, 
"the  morphological  changes  in  the  sperm- 

Development  of  spermatozoa.  ^  preceding  the  formation  of  the  Spermatic 

filaments  are  identical  in  their  character  with  the  changes  in  the  ovum 
which  are  antecedent  to  the  formation  of  the  new  being.  When  the  gen- 
erative function  begins  to  be  developed,  the  character  of  the  epithelial 
cells  lining  the  tubules  is  modified.  The  cells  pass  to  a  higher  degree 
in  function,  but  do  not  undergo  any  change  in  structure,  except  a  slight 
increase  in  size.  In  this  condition  they  divide  and  subdivide,  by  a  pro- 
cess similar  to  the  segmentation  of  the  yolk,  until  they  are  entirely  con- 
verted into  a  mulberry  mass.  A  liquefaction  of  the  segmented  contents 
into  a  minute  granular  blastema  then  ensues,  and  from  this  the  spermatic 
filaments  are  developed.  In  the  Plagiostomes,  Dr.  Burnett  was  able  to 


THE   GERM-CELL.  519 

observe  the  disappearance  of  the  mulberry  mass,  and  its  replacement  by 
a  fasciculus  of  spermatic  filaments,  although  the  exact  metamorphosis  by 
which  the  granular  cellular  mass  formed  the  bodies  of  the  spermatozoids 
could  not  be  detected.  The  spermatic  filaments,  Dr.  Burnett  thinks,  are 
not  formed,  as  stated  by  Kolliker,  by  a  deposit  from  the  contents  of  the 
sperm-cell  or  nucleus,  but  by  an  elongation  of  the  nucleus  itself.  The 
body  of  the  spermatozoid  is  developed  from  the  cell,  while  the  tail  is 
probably  subsequently  formed  by  an  accumulation  of  minute  particles." 
(Kolliker,  Am.  ed.,  p.  625.) 

In  man,  the  production  of  spermatozoa  commences  between  the  four- 
teenth and  sixteenth  year,  the  time  of  puberty,  and  continues  until  the 
sixty-fifth  or  seventieth,  or  even  much  longer.  This  period  of  commence- 
ment is  marked  by  a  great  change  in  the  physical  and  moral  constitution. 

The  spermatic  fluid  of  mule  animals  contains  no  spermatozoa.  This 
fact  has  been  established  in  an  interesting  manner  by  Wagner  in  the  case 
of  birds,  of  which  many  of  those  which  are  domesticated  readily  cross. 
There  can  be  no  doubt  that  these  bodies  are  the  essential  portion  of  the 
fluid,  and  that  it  is  their  action  upon  the  ovum  which  establishes  its  fer- 
tilization. 

There  has  been  much  controversy  whether  the  spermatozoa  present 
traces  of  organization,  properly  speaking.  Though  it  is  convenient  to 
designate  their  dilated  portion  as  the  head,  and  the  filament  as  the  tail, 
it  has  never  yet  been  established  that  any  thing  answering  to  a  true 
structural  arrangement  exists,  and,  upon  the  whole,  it  may  be  concluded 
that  the  appearances  which  have  been  by  some  supposed  to  indicate  or- 
ganization are,  in  reality,  only  an  optical  illusion. 

2d.  Of  the  Germ-cell. — In  mammals  the  female  reproductive  appara- 
tus consists  essentially  of  the  ovaries,  oviduct,  and  uterus.  Female 

The  ovaries  are  two  ovoid  bodies  situated  on  either  side  ductive  appa- 
of  the  uterus.  They  consist  of  a  stroma  in  which  vesicles  r 
are  imbedded :  these  vesicles  give  origin  to  the  ova.  In  the  manner  to 
be  presently  described,  the  ova,  being  received  at  the  fimbriated  extrem- 
ities of  the  Fallopian  tubes,  those  tubes  being  therefore  appropriately 
termed  oviducts,  are  carried  into  the  cavity  of  the  uterus. 

At  the  time  of  puberty  in  the  human  female,  which  occurs  between 
the  14th  and  16th  year,  a  physical  and  moral  change  takes 

i  .     ^  C-Vt.        t:  i        j        n    j    i  .      The  catamenia. 

place,  answering  to  that  which  has  been  already  alluded  to 
as  occurring  in  the  male.  From  this  period  a  sanguinolent  discharge 
makes  its  appearance  monthly :  it  is  the  catamenia.  The  interval  from 
time  to  time  is  commonly  estimated  at  four  weeks ;  it  varies,  however, 
with  individuals,  and  it  is  said  also  with  climates,  the  discharge  occurring 
in  the  hotter  more  frequently,  and  in  greater  quantity.  It  is  essentially 
blood,  which  has  been  deprived  of  its  quality  of  coagulating  by  inter- 


520  OVUM   IN   THE   OVARY. 

mixture  with  acid  mucus  of  the  vagina.  So  long  as  these  periods  con- 
tinue, the  individual  possesses  the  reproductive  power,  the  first  appear- 
ance of  the  catamenia  indicating  the  capacity  for  conception,  and  the  dis- 
appearance, at  about  the  45th  year,  its  end.  During  gestation  the  cata- 
menia are  suspended,  and,  indeed,  it  is  this  event  which  is  usually  taken 
as  the  indication  that  conception  has  occurred. 

The  periodical  occurrence  of  this  discharge  in  the  human  female,  though 
more  frequent,  is  essentially  the  same  as  the  periodically  occurring  heat 
of  other  animals,  which  is  also  attended  with  a  sero-sanguinolent  dis- 
charge. In  other  respects,  likewise,  the  analogy  is  maintained,  for  in 
those  animals,  the  appearance  of  this  discharge  and  its  attendant  phe- 
nomena constituting  an  indication  of  a  simultaneous  capacity  for  con- 
ception, in  women  the  same  thing  holds  good,  conception  occurring  in 
them  at  the  time  of  the  close  of  the  menstrual  discharge. 

I.   Ovum  in  the  Ovary. 

The  ovary  is  the  organism  in  which  the  ova  are  prepared,  these  bodies 
arising  in  the  following  way : 

In  the  stroma  of  the  ovary  there  occur  at  a  time  ten,  twenty,  or  many 
Production  more  cells,  which  have  received  the  designation  of  Graafian  ves- 
of  ova.  jcies  or  Ovisacs.  These  originate  in  the  interior  of  the  ovary, 
and,  as  they  become  perfected,  pass  to  its  surface,  presenting  themselves 
thereupon  as  prominences  which  are  covered  over  exteriorly  with  peri- 
toneum. Each  of  these  vesicles  has  a  membranous  envelope  connecting 
it  with  the  substance  of  the  ovary  exteriorly,  and  covered  interiorly  with 
a  layer  of  nucleated  cells,  designated  membrana  granulosa.  It  is  filled 
with  a  fluid  in  which  multitudes  of  granules  float,  and  in  its  centre  is  the 
ovule.  This,  as  it  becomes  mature,  is  pushed  up  toward  the  surface  of 
the  ovisac  by  an  accumulation  of  liquid  in  the  lower  part  thereof,  and 
is  so  brought  into  close  relation  with  the  membrana  granulosa  at  the 
place  where  it  is  upon  the  surface  of  the  ovary.  At  this  point  there  col- 
lects on  the  ovum  a  zone  of  granules,  to  which  the  designation  of  discus 
proligerus  is  given. 

Fig.  248,  transverse  section  through  the  ovary  of  a  woman  dead  in 
the  fifth  month  of  pregnancy :  <z,  Graafian  follicle  of  inferior,  and,  £,  of 
superior  surface ;  c,  peritoneal  lamella  of  ligamentum  latum,  continued 
Upon  the  ovary,  and  coalescing  with,  d,  the  tunica  albuginea :  in  the  in- 
terior two  corpora  albicantia  (old  corpora  lutea)  are  visible;  £,  stroma  of 
the  ovary.  (Kolliker.) 

Fig.  249,  section  of  the  Graafian  vesicle :  1,  stroma  of  ovary,  with 
blood-vessels  ;  2,  peritoneum ;  3  and  5,  layers  of  the  external  coat  of  the 
Graafian  vesicle ;  4,  membrana  granulosa ;  6,  fluid  of  the  vesicle ;  7,  gran- 
ular zone,  or  discus  proligerus ;  8,  the  ovum.  (Von  Bar.) 


Fig.  250. 


521 


Section  of  Graafian  vesicle. 


Ovum. 


Section  of  ovary. 

Fig.  250,  ovum  of  the  sow  :  1,  germinal  spot  ;  2,  germinal  vesicle  ; 
3,  yolk  ;  4,  zona  pellucida  ;  5,  discus  proligerus  ;  6,  adherent  granules  or 
cells.  (Barry.) 

The  diameter  of  the  human  ovum  varies  from  the  yj-^  to  the  -^g-  of 
an  inch.  It  consists  of  an  exterior  transparent  membrane,  Description  of 
the  Y^fr  o"  °f  an  inck  *n  thickness,  which,  when  compressed  the  ovum- 
for  the  purpose  of  examination,  appears  like  a  diaphanous  circle,  and  hence 
called  zona  pellucida.  Within  this  zone,  and  inclosed  by  it,  is  the  yolk, 
a  granular  material  suspended  in  or  intermingled  with  fluid,  the  granules 
being  of  different  sizes  ;  those  near  the  pellucid  zone  are  the  largest.  For 
the  most  part,  the  yolk  consists  of  albumen  and  oil  globules.  '  Its  condi- 
tion, as  regards  liquidity,  varies  in  different  animals  ;  in  some  it  is  al- 
most a  soft  solid,  so  that,  when  water  percolates  through  the  zona  pellu- 
cida, it  isolates  the  yolk  by  surrounding  it  on  all  sides,  and  parting  it  off 
from  the  zone.  Within  the  substance  of  the  yolk  is  a  distinct  cell,  the 
germinal  vesicle,  which  gradually  makes  its  way  from  the  interior  to  the 
place  of  peritoneal  contact.  As  it  advances  to  perfection,  it  consists  of  a 
delicate  spherical  membrane  containing  a  liquid,  in  which  granules  are 
suspended.  Upon  that  portion  of  it  nearest  to  the  place  of  peritoneal 

contact  is  its  nucleus,  the  germinal 
spot,  about  the  -8  0*0  0  of  an  inch 
in  diameter,  and  consisting  of  yel- 
low granules. 

Fig.  251,  diagram  of  a  Graa- 
fian vesicle  and  ovum  :  1,  stroma 
of  ovary  ;  2,  3,  external  and  in- 
ternal tunics  of  the  Graafian  ves- 
icle ;  4,  cavity  of  vesicle  ;  5,  thick 
tunic  of  the  ovum  or  yolk-sac  ;  6, 
the  yolk  ;  7,  the  germinal  vesicle  ; 
8,  the  germinal  spot. 

The  most  mature  ova  are  near- 
est the  surface  of  the  ovary,  but 
Diagram  of  Graafian  vesicle.  are  separated  from  its  peritoneum 


251. 


522 


COEPUS   LUTEUM. 


Corpus  luteum. 


by  a  thin,  fibrous  layer  of  stroma.  The  Graafian  vesicle  is,  there- 
fore, the  parent  of  the  ovum.  Periodically,  as  development  is  going  on, 
the  Graafian  vesicle  bursts,  and  the  ovum  is  set  free.  This  effect  arises, 
in  part,  from  the  circumstance  that,  the  space  between  the  vesicle  and 
ovum  being  filled  with  cells,  those  near  the  surface  of  the  ovary  disap- 
pear, and  an  albuminous  liquid,  which  accumulates  below,  pushes  the 
ovum  up.  This  extrusion  of  ova  occurs  even  in  childhood.  The  ovisac, 
or  Graafian  vesicle,  thus  changed  into  a  follicle,  is  gradually  filled  up,  its 
walls  wrinkling,  and  red-colored  material,  arising  from  the  membrana 

granulosa,  being   deposited  in  it  until  it  is   almost  filled. 

This  deposit  gradually  turns  yellow,  and  is  eventually  com- 
posed of  cells  interiorly,  and  fibres  arising  therefrom  exteriorly.  When 
the  deposit  is  completed,  a  stellated  cicatrix  is  observed  in  its  midst. 
The  yellow  body  thus  arising  passes  under  the  designation  of  corpus  lu- 
teum. If  impregnation  does  not  occur,  the  yellow  substance  forms  to 
but  a  small  extent,  and  after  a  time  disappears.  It  is  relatively  more 
abundant  in  animals  than  in  women.  Attempts  have  been  made  to  use 
the  indications  of  the  corpus  luteum  for  determining  the  question  of  preg- 
nancy. The  following  points  are  presented  by  Dr.  Dalton  as  offering 
characteristics  by  which  the  corpora  lutea  of  pregnancy  and  menstruation 
may  be  distinguished  :  "  The  corpus  luteum  of  pregnancy  arrives  more 
slowly  at  its  maximum  development,  and  afterward  remains  for  a  long 
time  as  a  noticeable  tumor  instead  of  undergoing  rapid  atrophy.  It  re- 
tains a  globular  or  only  slightly  flattened  form,  and  gives  to  the  touch  a 
sense  of  resistance  and  solidity.  It  has  a  more  advanced  organization 
than  the  other  kind,  and  its  convoluted  wall  is  much  thicker.  Its  color 
is  not  of  so  decided  a  yellow,  but  of  a  more  dusky  hue,  and  if  the  period 
of  pregnancy  is  at  all  advanced,  it  is  not  found,  like  the  other,  in  com- 
pany with  unruptured  vesicles  in  active  process  of  development." 

Fig.  252,  corpora  lutea  of  different  periods  :    a,  corpus  luteum  two 

Fig.  252. 


Corpora  lutea. 


days  after  delivery ;  I,  corpus  luteum  of  about  sixth  week  after  impreg- 
nation, showing  its  plicated  form  at  that  period ;  1,  substance  of  ovary ; 
2,  substance  of  corpus  luteum  ;  3,  grayish  coagulum  in  its  cavity ;  d,  in 


OVUM   IN   THE   OVIDUCT.  523 

the  twelfth  week  after  delivery,     (a  and  b,  Dr.  Patterson  ;  d.  Dr.  Mont- 
gomery.) 

II.  Fertilized  Ovum  in  the  Oviduct. 

Such  being  a  description  of  the  ordinary  or  unfertilized  ovum,  we  have 
next  to  follow  the  changes  which  ensue  if  fertilization  has  taken  place. 

The  spermatozoa  having  become  enveloped  in  the  pellucid  zone  or 
passing  through  it,  the  ovum  is  received  by  the  iimbriated  extremities 
of  the  Fallopian  tube,  along  which  it  is  carried  by  peristaltic  contraction 
or  ciliary  motion.  The  first  change  which  takes  place  in  it  is  the  disap- 
pearance of  its  germinal  vesicle  and  germinal  spot.  This  disappearance 
is,  however,  stated  by  some  to  be  preceded  by  a  development  of  cells 
originating  in  the  nucleus  or  germinal  spot ;  nor  is  it  the  result  of  fertil- 
ization, since  it  occurs  in  the  unimpregnated  ovum.  The  Chano.es  of  the 
cells  of  the  membrana  granulosa,  which  surround  the  ovum,  fertilized  ovum 
become  first  of  a  conical  shape,  but  their  rounded  form  is  re- 
sumed on  passing  into  the  tube. 

Fig.  253.  Fig.  253,  ovarian  ovum  of  dog,  exhibiting  the 

elongated  form  and  stellate  arrangement  of  the 
cells  of  the  discus  proligerus  round  the  zona  pel- 
lucida. 

Fig.  254,  same  ovum  after  the 
removal  of  most  of  the  club- 
shaped  cells. 

The  yolk  is  next  observed  to 
ovarian  ovum.  contract  so  as  to  leave  a  clear 

space  between  it  and  the  zona  pellucida.  As  the  pas- 
sage along  the  tube  is  taking  place,  the  zona  assumes 
a  coating  of  albuminous  material,  which  is  what  is  call- 
ed  in  birds  the  white  of  the  egg.  It  eventually  becomes  the  chorion. 
Meantime,  after  the  disappearance  of  the  germinal  vesicle,  a  new  cell,  the 
embryo  cell,  arises,  and  this  undergoes  subdivision  or  segmentation,  an 
effect  in  which  the  yolk  itself  presently  becomes  involved,  each  new  or 
daughter  embryo  cell  so  arising  assuming  a  part  of  the  yolk.  A  constant 
process  of  bisection  is  thus  established,  the  yolk  dividing  first  into  two 
portions,  then  into  four,  eight,  sixteen,  etc.,  each  division  containing  a 
nucleated  cell.  At  this  period  may  be  seen  the  spermatozoa  involved  in 
the  zona  pellucida,  and,  as  the  process  of  bisection  goes  on,  The  mulberry 
the  mass  assumes  a  mulberry  aspect,  and  finally  becomes  mass- 
granular.  This  is,  for  the  most  part,  finished  by  the  time  the  ovum  en- 
ters the  uterus. 

Fig.  255,  ova  of  the  dog  in  various  stages :  a,  from  the  oviduct,  half 
an  inch  from  the  uterus,  spermatozoids  being  in  the  pellucid  zone,  the  yolk 


524 


SEGMENTATION   OF   OVUM. 


bisected ;  b,  cells  of  tunica  granulosa  have  disappeared,  and  the  yolk  is 
in  four  segments ;  c,  continued  advance  in  segmentation ;  d,  the  zona 
has  become  thicker,  and  the  segmentation  more  complete ;  e,  ovum  burst 
by.  compression :  some  of  the  segments  have  escaped ;  each  shows  a 
bright  spot  or  vesicle. 

Fig.  255. 


Segmentation  of  ovum. 

Fig.  256,  cleavage  of  the  yolk  after  fecundation :  #,  an  ovum  of  As- 
caris  nigrovenosa,  the  yolk  of  which  is  divided  into  two  equal  portions ; 
the  upper  portion  contains  a  cell  with  a  large  nucleus,  the  lower  a  sim- 
ilar cell  with  two  small  nuclei ;  &,  ovum  subdivided  into  four  portions ; 
c,  the  subdivision  has  reached  sixteen,  each  possessing  a  mono-nucleated 
cell ;  d,  ovum  of  Ascaris  acuminata,  showing  the  stages  of  subdivision, 
the  portions  becoming  very  small ;  6,  the  portions  preparing  to  be  mould- 
ed into  the  young  worm,  (#,  &,  c,  Kolliker ;  d,  e,  Bagge.) 

Fig.  256. 


Segmentation  of  ovum. 

As  the  ovum  is  about  to  enter  the  uterus,  each  portion  which  has  arisen 
from  the  segmentation  of  the  yolk  has  become  a  perfect  cell.  This  cell 
formation  having  been  accomplished  at  the  surface  of  the  yolk  first,  the 
cells  there  begin  to  coalesce  into  a  membrane,  with  an  aspect  like  that 
of  hexagonal  pavement  epithelium,  and,  as  the  change  passes  toward  the 
centre,  the  cells,  as  they  form,  come  toward  the  membrane  and  thicken 
it,  leaving  a  clear  liquid  within.  In  this  manner  a  secondary  vesicle 
forms  within  the  zona  pellucida :  it  is  the  blastodermic  vesicle :  it  is  the 


UTERINE  NUTRITION.  525 

temporary  stomach  of  the  embryo.  Its  wall  constitutes  the  germinal 
membrane,  upon  which  the  embryo  arises.  New  cells  being  constantly 
added,  the  membrane  increases  in  thickness ;  and  here  it  may  ^he  germinal 
be  remarked  that,  in  most  types,  the  yolk  is  to  be  considered  membrane, 
as  presenting  two  portions — the  germ-yolk  and  the  food-yolk ;  the  for- 
mer being  immediately  employed  in  the  development  of  the  embryo,  and 
the  latter  being  a  stock  for  more  advanced  supply.  In  mammals,  for 
whom  other  means  of  nutrition  are  quickly  provided,  the  food-yolk  is  im- 
perceptible, and,  moreover,  in  them  the  albuminous  coating  of  the  zona 
pellucida  is  small ;  but  in  birds,  the  embryo  of  which  has  to  be  nourish- 
ed independently  of  the  parent,  the  quantity  is  necessarily  large.  As  we 
have  sai'd,  this  albuminous  covering  and  the  zona  together  constitute  the 
chorion,  the  exterior  of  which  presents  a  rugged  aspect,  from  the  appear- 
ance of  absorbing  radicles,  which,  becoming  imbedded  or  dove- 
tailed in  the  deciduous  membrane,  presently  to  be  described, 
establishes  the  necessary  connection  for  tuft  nutrition,  and  thereby  ob- 
taining albumen  from  the  parent. 

III.  Fertilized  Ovum  in  the  Uterus. 

While  the  ovum  is  passing  through  the  Fallopian  tube  or  oviduct,  it 
obtains  a  coating  of  albuminous  material  outside  of  its  zona  pellucida,  as 
has  been  said.  This  coating  becomes  the  means  of  attachment  to  the 
uterus,  and  thereby  of  the  absorption  of  nutriment  in  the  following  way. 
The  outside  surface  of  the  incipient  chorion  presents  a  layer  of  cells, 
and  soon  after  assumes  a  fibrous  structure.  In  this  condi-  uterine  nutri- 
257.  tion  the  ovum  makes  its  appearance  in  tion- 

the  uterus,  on  the  interior  of  the  surface  of  which  the 
mouths  of  a  great  number  of  follicles  open.  These 
follicles  are  not  unlike  those  which  the  stomach 
presents.  Their  general  appearance  is  illustrated  by 
Fig.  257;  d,  csecal  terminations  of  glands;  e,  their 
tubes  ;  «,  mouths  on  interior  of  uterus.  The  con- 
stitutional disturbance  which  is  at  this  time  taking 
place,  enhanced  by  the  presence  of  the  ovum  in  the 
organ,  at  once  increases  its  vascularity ;  the  follicles 
become  larger,  cells  are  abundantly  developed  in 
them,  and  the  uterine  cavity  is  filled  with  a  liquid 
containing  many  nucleated  cells.  This  plastic  semi- 
fluid material  receives  the  fringes  of  the  villous  coat 
of  the  chorion,  which  are  now  being  developed ;  and 
these  even  find  their  way  into  the  mouths  of  the 
**  glandular  tubes ;  from  this  exudation  or  secretion 
uterine  tubes.  the  membrana  decidua  forms,  though  by  some  it  is 


526  MEMBRANA  DECIDUA  AND   PLACENTA. 

Formation  of  represented  as  being  a  metamorphosis  of  the  mucous  mem- 
membrana  de-  brane  itself.  Meantime  the  ovum  is  itself  coated  over  with  a 
corresponding  membrane,  designated  membrana  reflexa,  be- 
cause it  was  believed  by  Mr.  Hunter  to  originate  in  the  circumstance 
that,  when  the  ovum  reached  the  uterine  mouth  of  the  Fallopian  tube,  it 
there  encountered  the  proper  membrana  decidua,  and,  not  perforating  it, 
but  bearing  it  onward,  gathered  a  fold,  covering,  or  envelope,  which, 
from  its  having  thus  been  formed  by  a  reflexion,  was  appropriately  des- 
ignated by  the  term  specified.  It  is,  however,  now  admitted  that  this 
description  of  the  formation  of  the  membrana  reflexa  is  erroneous,  for  in 
reality  the  ovum  is  at  no  time  on  the  outside  of  the  mucous  membrane, 
which  is  continuous  from  the  cavity  of  the  uterus  through  the  Fallopian 
tube.  The  following,  therefore,  seems  to  be  the  more  correct  description. 
The  presence  of  the  ovum  gives  rise  to  an  increased  development  of  cells, 
which  rapidly  spread  around  it,  and  coat  it  all  over,  their  points  of  origin 
being  those  portions  of  the  uterine  mucous  membrane  with  which  the 
ovum  is  in  contact.  In  this  way  it  receives  its  deciduous  envelope, 
which,  participating  duly  in  its  growth,  is  at  the  end  of  the  third  month 
in  contact  with  the  uterine  decidua  all  over. 

At  the  stage  we  are  now  considering,  the  nutrition  of  the  embryo  is 
conducted  in  a  special  but  very  temporary  way.  The  yolk  of  the  ovum 
has  no  stock  of  food  to  maintain  the  nutritive  processes  beyond  the  brief 
space  which  transpires  in  the  passage  through  the  Fallopian  tube.  The 
duty  of  nutrition  is  at  this  moment  assumed  by  the  villous  coat  of  the 
chorion,  which  absorbs  fluid  exuding  from  the  uterine  decidua  very 
much  after  the  manner  of  the  spongioles  of  a  plant ;  but  almost  imme- 
diately the  necessity  arises  of  diverting  more  directly  the  albumenoid 
material  to  the  quickly-growing  embryo  from  the  yolk-bag,  to  which  it 
would  have  gone,  and  this  new  destination  implies  the  introduction  of 
new  channels  of  transport,  which,  under  the  form  of  a  vascular  appara- 
tus, are  now  provided. 

About  the  close  of  the  second  month,  a  proper  vascular  apparatus  for 
the  combined  purposes  of  nutrition,  secretion,  and  respiration 

The  placenta.          ,         '.  .        ,         ,  _  .  f     .      . 

makes  its  appearance:  it  is  the  placenta.  Its  origin  is  in 
the  little  blood-tubes  which  form  in  the  tufts  of  the  chorion,  in  man  at 
one  point,  in  ruminants  simultaneously  at  several,  giving  rise  in  the  for- 
mer case  to  one  organ,  the  placenta,  as  has  been  said,  in  the  other  to 
many  such,  or,  at  all  events,  to  one  of  a  composite  structure,  the  cotyle- 
dons. The  foetal  vessels  thus  arising  in  the  villi  of  the  chorion  become 
intermingled  with  vessels  contemporaneously  arising  from  the  uterus ; 
and  though,  in  some  cases,  this  intermingling  is  less  complicated,  so  that 
the  maternal  and  fostal  portions  are  separable,  in  man  the  internetting  is 
complete,  the  principle  being  to  bring  the  foetal  vascular  tufts  in  such  a 


DIVISION   OF  THE   GERMINAL  MEMBRANE. 


527 


relation  with  the  maternal  blood-sinuses,  by  the  tufts  dipping  Functions  of 
down  or  being  enveloped  therein,  that  the  completest  con-  the  Placenta- 
tact  and  facility  of  exchange,  but  not  of  intermixture,  may  be  insured. 
Things  are  arranged  in  such  a  way  that  the  maternal  and  foetal  blood  do 
not  intermingle,  each  being  confined  in  vessels  of  its  own,  through  the  thin 
walls  of  which  nutritious  matter  may  pass  and  excrementitious  matter  re- 
pass.  Every  foetal  tuft  has  a  deciduous  layer  upon  it,  and  the  blood 
brought  by  the  curling  arteries  of'the  uterus  furnishes  to  the  foetus  its  ox- 
ygen, and  receives  back  carbonic  acid,  with  other  excrementitious  matters. 
In  this  respect,  respiration  is  carried  on  by  the  aid  of  a  mechanism  which 
answers  to  the  gills  of  fishes,  the  maternal  arterial  blood  standing  for  the 
aerated  water ;  but,  besides  this,  the  tufts  have  another  duty  to  dis- 
charge— the  obtaining  of  albumenoid  material  from  the  maternal  blood. 
The  placental  mechanism  is  therefore  much  more  perfect  in  its  action 
than  the. tuft  mechanism  which  preceded  it. 

The  germinal  membrane,  formed  as  has  been  described,  already  ex- 
hibits at  one  spot  an  opaque  area  of  a  roundish  shape,  con-  change* in  the 

Fiq  258  Sisting  Of  Cells  and  granules.       To    germinal  mem- 

^  G  brane,andpro- 

this  the  designation  of  germinal  duction  of  lay- 
area  is  given.  At  this  area  the  ers- 
membrane  next  becomes  divisible  into  t\vo 
laminaa,  and  eventually  throughout  its  whole 
extent,  as  seen  in  Fig.  258.  Of  these  lam- 
inae, the  exterior,  which  is  nearer  to  the  zona 
pellucida,  is  the  serous  layer.  It  is  the  raised 
membrane  of  the  figure,  and  in  it  are  to  be 
developed  the  nervous  and  muscular  systems 
of  the  embryo.  The  interior  is  designated  the  mucous  layer,  and  from 
Fig.  259.  this  arise  the  digestive  organs. 

The  germinal  area  by  degrees 
loses  its  circular  form  and  becomes 
oval,  its  central  portions  clearing 
off  and  giving  rise  to  the  area  pel- 
lucida. Around  this  the  opacity 
is  increased,  and  in  it  blood-ves- 
sels appear;  hence  to  this  dark  cir- 
cle the  designation  of  area  vascu- 
losa  is  applied.  In  the  pellucid 
zone  is  next  seen  a  delicate  line, 
the  primitive  groove,  T'he  primitive 

Fig.  259.       It  OCCUrS   groove  and 

in   the    serous    layer  dorsal  laminie' 

The  primitive  groove,  magnified  8  diameters.          Only,  IS  Wider  at  one  end  than  at 


528 


VERTEBRAL   COLUMN. 


Fig.  260. 


Origin  of  the  train  upon  the  spinal  cord,  magnified  8 
diameters. 


the  other,  the  wider  part  being  destined  for  the  head  of  the  embryo. 
On  each  side  of  the  primitive  groove  two  oval  areas  of  cells  emerge : 
they  are  the  dorsal  laminae.  They  rise  up  to  cover  in  the  primitive 
groove,  so  as  to  convert  it  into  a  tube,  with  three  bead-like  swellings  at 
its  wider  end,  the  elements  of  the  prosencephalon,  mesencephalon,  and 

epencephalon,  Fig.  260.  The  ex- 
planation of  this  and  the  preced- 
ing figure  have  already  been  given 
on  p.  293.  On  the  internal  part 
of  the  lamina  nervous  matter  be- 
gins to  form,  the  rudiment  of  the 
cerebro-spinal  axis.  In  the  bot- 
tom of  the  groove  is  the  trace, 
chorda  dorsalis.  The  groove  it- 
self, converted  into  a  tube,  con- 
stitutes the  central  canal  of  that 
axis,  its  completion  into  the  tu- 
bular shape  occurring  first  in  the 
middle,  and  then  up  and  down. 
The  form  of  the  lateral  masses  va- 
ries as  development  goes  on. 
A  line  of  cells  running  lengthwise  in  the  primitive  groove  is  the  origin 
Chorda  dorsa-  of  the  chorda  dorsalis,  on  which  the  rudiments  of  the  verte- 
and~^vascuiar  kral  c°lumn  appear.  In  the  amphioxus  and  myxenoid  fishes 
system.  development  in  this  direction  stops  at  this  point,  the  chorda 

dorsalis  being  the  permanent  structure.  The  vertebrse  now  emerge  un- 
der the  aspect  of  square  plates,  and  the  dorsal  laminse,  prolonging  them- 
selves outward  and  downward,  as  it  were,  by  an  offshoot,  produce  the 
ventral  laminse,  which  close  in  the  abdominal  walls,  and  so  form  the 
boundaries  of  the  trunk.  Simultaneously  a  new  layer  of  cells  arises  be- 
tween the  serous  and  mucous  layer  of  the  germinal  membrane,  at  the  area 
vasculosa,  and  in  this  intercalated  lamina  the  vascular  system  forms  and 
blood  corpuscles  appear,  capillary  vessels  arising  from  the  coalescence  of 
nucleated  cells,  the  touching  ends  of  which  become  pervious.  As  the 
process  goes  forward,  a  network  of  such  vessels  is  constructed,  and  it  is 
to  be  particularly  remarked  that  this  takes  place  and  that  the  blood  is  in 
circulation  prior  to  the  existence  of  the  heart.  Around  the  extending 
blood-vessels  or  vascular  area  runs  a  circular  capillary  called  the  terminal 
sinus  in  the  first  stage  of  the  process,  but  this  disappears  as  the  vessels 
extend  all  over  the  germinal  membrane.  The  extension  of  these  vessels 
is  in  part  accomplished  by  the  cells  from  which  they  have  arisen  elon- 
gating themselves  into  processes. 

Fig.  261,  first  appearance  of  blood-vessels  in  vascular  layer  of  germ- 


PRODUCTION   OF   VESSELS. 


529 


Production  of  vessels. 


Fig.  261.  inal  membrane  of  a  fowl  at  thirty-sixth  hour  of  in- 

cubation.    (Wagner.) 

The  formation  of  vessels  from  the  coalescence 
of  nucleated  cells,  the  touching  ends  becoming 
pervious  or  elongating,  is  continued  to  a  much 
later  period  of  development,  as  is  demonstrated  by 
Fig.  262. 

Capillary  lymphatic  from  the  tail  of  the  tadpole :  #,  membrane ;  b, 
Fig-  262.  processes  formed  by  it ;    c,  re- 

mains of  the  contents  of  the 
cells  forming  these  vessels,  in 
which  nuclei  are  concealed;  0, 
ccecal  terminations  of  the  ves- 
sels ;  jf,  one  of  these  termina- 
tions still  recognizable  as  a  form- 
ative cell ;  g,  isolated  formative 
cells  about  to  join  with  actual 
vessels,  magnified  350  diame- 
ters. (Kolliker.) 

It  is  at  this  tirns  that  nutri- 
tion  by  cells  ceases,  and  vascu- 
lar nutrition  commences,  as  pre- 
viously described.  The  embryo 
has  now  become  too  large  for 
promiscuous  cell  nutrition  to  an- 
swer ;  moreover,  development  is 
required  to  take  place  at  differ- 

Production  of  vessels)  capillary  lymphatic,  magnified  350    Cnt  rateS  at  isolated  and  Special 

points.     The  formation  of  the 
amnion  coincides  with  these  events. 

The  heart  appears  first  as  a  canal  or  tube,  arising  in  the  vascular 
layer  from  a  columnar  mass  of  cells,  of  which  the  inner  ones  Development 
have  deliquesced  to  form  a  tube.     This  then  becomes  tri-  of  the  heart- 
chambered,  containing  an  auricle,  a  ventricle,  and  the  bulbus  arteriosus, 
Fig  263  Fig.  263,  of  which  a  description  is 

given  on  p.  135.  Subsequently  the 
auricle  and  ventricle  are  each  divi- 
ded by  septa,  that  in  the  ventricle 
being  commenced  about  the  fourth, 
and  finished  about  the  eighth  week. 
The  auricular  septum  is  not  completed  until  after  birth. 

Fig.  264,  page  530,  shows  the  human  heart  at  about  the  fifth  week : 
A,  the  heart  opened  on  the  abdominal  aspect;  1,.  the  bulbus  arteriosus; 

LL 


Rudimentary  heart. 


530  THE   AMNION. 

2,  2,  two  aortic  arches,  uniting  posteriorly 
to  form  the  aorta ;   3,  the  auricle  ;   4,  the 
opening  from  the  auricle  into  the  ventricle, 
6,  which  is  laid  open ;  5,  the  septum  rising 
from  the  lowest  part  of  the  cavity  of  the  ven- 
tricle ;   7,  the  vena  cava  inferior :  B,  view 
from  behind ;  1,  the  trachea ;  2,  the  lungs  ; 

3,  the  ventricle ;  4,  5,  the  large  atrium  cor- 
Fcetai  heart.                  dis,  or  auricle ;    6,  the  diaphragm ;   7,  the 

aorta  descendens;  8,  the  pneumogastric ;  9,  its  branches ;  10,  its  continu- 
ation. (Von  Bar.) 

As  soon  as  the  capillary  system  is  fairly  established,  the  change  in 
the  character  of  the  function  of  nutrition  alluded  to  is  accomplished,  and 
in  those  animals  which  depend  for  their  development  on  a  food  yolk,  it 
is  eventually  entirely  covered  with  ramifications  of  these  vessels.  The 
blood-cells  of  the  first  order  or  series  are  evolved  from  the  nuclei  of  the 
cells  which  coalesced  for  the  formation  of  blood-vessels. 

The  development  of  the  embryo  still  continuing,  it  assumes  a  form 
Elevation  of  which  has  been  aptly  described  as  resembling  that  of  a  boat 
the  embryo.  piace(j  UpSi(Je  down,  the  bottom  of  the  boat  rising  higher  and 
higher  above  the  surface  of  the  germinal  membrane,  and  lifting  with  it 
that  portion  of  the  membrane  to  which  it  is  attached.  The  two  ends  of 
the  boat-shaped  body  bend  under  toward  one  another ;  the  larger  of  the 
two  is  destined  to  become  the  head  of  the  embryo.  As  this  elevation 
takes  place,  the  embryo  becomes  separated  by  a  constricted  space  from 
the  surrounding  germinal  membrane,  its  abdominal  parietes  being  still 
open  and  in  contact  with  the  yolk.  From  the  layer  which  thus  lines 
the  interior  of  the  cavity  of  the  embryo,  the  intestinal  canal  arises  as  a 
tube  from  the  coalescence  of  a  pair  of  lateral  ridges,  and  the  surrounding 
and  exterior  portions  of  the  germinal  membrane,  elevating  themselves 
above  the  constricted  space,  coalesce  over  the  back  of  the  embryo,  and 
thus  inclose  it  in  a  sac.  This  sac  constitutes  the  amnion, 

Theammon.  .  .      ' 

and  in  this  manner,  by  folding,  the  interior  of  the  germinal 
membrane  is  used  as  a  digestive  surface,  the  outer  as  one  for  secretion. 
The  umbilical  cord  obtains  a  sheath  from  the  amnion,  which  at  one  end 
is  continuous  with  the  skin  of  the  foetus,  and  the  other  is  reflected  over 
the  surface  of  the  placenta.  The  amnion  therefore  constitutes  a  closed 
sac,  which  contains  a  fluid,  the  liquor  amnii. 

The  place  at  which  the  germinal  membrane  is  constricted,  so  as  to  be 
able  to  act  as  a  digestive  surface  to  the  embryo,  though  linear  at  first,  is 
gradually  narrowed  down,  and  constitutes  the  umbilicus.  This  .con- 
stricted part  is  now  the  omphalo-mesenteric  duct,  which  of  course  com- 
municates with  the  cayity  of  the  yolk-sac,  which,  at  this  stage  of  devel- 


THE  CIRCULATORY  SYSTEM.  531 

opment  in  mammalia,  is  the  umbilical  vesicle.  In  birds,  the  yolk-sac  is 
carried  completely  into  the  abdomen  through  the  umbilical  opening ;  in 
mammals  it  remains  exterior.  It  does  not  appear  that  the  contents  of 
the  yolk  are  directly  absorbed  from  «the  cavity  of  the  sac,  but  they  are 
carried  by  the  ramifying  vessels  to  the  liver.  These  vessels  are  there- 
fore counterparts  of  the  mesenteric.  Eventually  folds  arise  on  the  lin- 
ing membrane  of  the  yolk-sac  over  which  these  vessels  pass,  and  which 
facilitate  absorption.  In  fish,  at  this  stage,  the  yolk-bag  hangs  down, 
and  respiration  takes  place  upon  its  surface. 

From  the  caudal  extremity  of  the  embryo  the  allantois  emerges  as  a 
mass  of  cells,  of  which  the  interior  liquefy,  and  the  exterior* 

T         .  *  .    <7'         ,        ..  ,          The  allantois. 

then  constitute  a  sac.  In  birds  and  in  reptiles  it  reaches 
considerable  development ;  in  the  former  extending  entirely  over  the 
yolk-sac,  but  in  mammals  it  is  soon  replaced  and  shrivels  up.  It  dis- 
charges the  function  of  a  urinary  bladder,  and,  indeed,  a  portion  of  it 
continues  to  do  so  in  man.  Its  disappearance  is  the  signal  that  the  em- 
bryo is  now  depending  on  the  placenta. 

To  return  now  to  the  development  of  the  circulatory  system.  At 
about  the  end  of  the  eighth  week,  as  we  have  seen,  the  ven-  Development 
tricle  is  divided  by  a  septum,  the  division  of  the  auricle  not  of  the  circuia- 
occurring  till  a  little  after,  and  even  then  not  being  perfect,  tory  syst' 
an  aperture,  the  foramen  fcvale,  existing.  This  is  the  state  of  things  at 
about  the  twelfth  week:  of  the  five  branchial  arches  two  disappear, 
the  aortic  bulb  then  divides  into  two  tubes,  which  .are  to  be  the  aorta 
and  pulmonary  artery  respectively.  Next,  one  of  the  branchial  arches 
forms  the  subclavian  and  carotid  arteries.  Of  the  middle  pair,  the  right 
is  obliterated,  but  the  left  remains  to  constitute  the  arch  of  the  aorta. 
Of  the  lowest  pair,  the  right  forms  the  right  and  left  pulmonary  arteries, 
and  the  left  constitutes  the  ductus  arteriosus. 

The  blood-system  having  reached  its  full  development,  the  foetal  circu- 
lation may  be  described  us  follows :  From  the  placenta  ox-  The  f^i  cjr. 
idized  blood  is  brought  through  the  umbilical  vein,  a  part  cuiation. 
passing  into  the  ascending  cava  through  the  ductus  venosus,  and  the  rest 
into  the  liver  through  the  vena  portas,  from  which,  by  the  hepatic  vein, 
it  also  reaches  the  ascending  cava.  In  its  passage  to  the  heart  it  be- 
comes adulterated  with  blood  derived  from  the  trunk  and  lower  extrem- 
ities. It  next  gains  into  the  right  auricle,  and,  to  some  extent,  is  kept 
from  contamination  with  the  venous  blood  coining  through  the  descend- 
ing cava  by  means  of  the  Eustachian  valve,  which  directs  the  arteri- 
alized  blood  through  the  foramen  ovale  into  the  left  auricle,  from  which 
it  gains  the  left  ventricle,  and  also  directs  the  venous  blood  of  the  de- 
scending cava  into  the  right  ventricle.  The  blood  which  is  in  the  left 
ventricle  is  driven  therefrom  into  the  ascending  aorta,  and  supplies  the 


532  TYPES   OF   NUTRITION. 

head ;  but  the  venous  blood  which  is  in  the  right  ventricle  is  driven 
therefrom  through  the  pulmonary  artery  and  ductus  arteriosus  into  the 
descending  aorta,  and,  mingling  with  the  arterial  blood  therein,  passes 
to  the  trunk  and  legs.  Of  this  blood  a  portion  is  then  carried  to  the 
placenta  to  be  arterialized. 

At  the  moment  of  birth  a  change  takes  place  in  the  manner  of  the  cir- 
culation, which  is  now  arranged  upon  the  type  described  at  page  134. 
This  is  accomplished  as  described  at  page  148. 

From  the  description  which  has  thus  been  given,  it  may  be  gathered 
Three  types  of  ^at»  UP  to  ^G  period  of  birth,  three  distinct  types  of  nutri- 
nutrition.  « tion  have  been  followed.  They  may,  with  sufficient  accura- 
cy, be  designated,  1st.  Yolk  nutrition ;  2d.  Tuft  nutrition  ;  3d.  Placental 
nutrition.  To  these  may  be  added  the  two  followed  at  a  later  period : 
4th.  Lactation,  and,  after  the  dental  mechanism  is  supplied,  5th.  The  diet 
of  mature  life. 

Respecting  the  development  of  special  organs,  it  may  be  remarked  that 
The  vertebral  °f  those  which  are  permanent,  the  vertebral  column  is  one  of 
column.  the  first  to  appear ;  it  shows  itself  under  the  form  of  isolated 
quadrangular  elements.  The  gelatinous  cellular  structure,  chorda  dorsa- 
lis,  acquires  a  sheath,  which  assumes  a  fibrous  structure,  and  from  this, 
in  the  lower  vertebrates,  the  vertebrae  are  evolved.  In  man,  the  ele- 
mentary quadrangular  plates  are  considered  tcfhave  an  independent  ori- 
gin. As  they  increase  in  number  and  size  they  surround  the  chorda, 
and  projections  springing  from  their  superior  surface  form  arches  to  en- 
velop the  spinal  cord.  Each  vertebra,  therefore,  is  constructed  by  the 
union  of  two  pieces,  one  on  either  side.  These  first  assume  the  condi- 
tion of  cartilage,  and,  later,  the  body  and  arches  ossify  from  separate 
points.  The  chorda  dorsalis,  which  has,  during  this  development,  been 
gradually  evolved  in  the  bodies  of  the  vertebrae,  disappears. 

The  bones  of  the  skull  are  metamorphosed  vertebras,  of  which,  accord- 
ing to  Professor  Owen,  four  appear  to  have  undergone  change.  To  these 
the  auditory,  gustative,  optic,  and  olfactory  nerves  are  respectively  re- 
lated, in  the  same  manner  that  the  spinal  nerves  are  to  their  vertebra. 

In  the  descriptions  given  in  the  preceding  part  of  this  work,  incident- 
Development  al  allusion  to  a  sufficient  extent  has  been  made  to  the  devel- 
tus^f  organic  °Pment  °^  most  of  the  apparatus  of  organic  and  also  animal 
life.  life.  It  may  therefore  here  be  briefly  stated  that  the  ali- 

mentary canal  originates  in  the  pinching  off  of  a  part  of  the  blastodermic 
vesicle  below  the  spinal  column.  At  first  it  is  a  straight  tube,  which 
communicates  about  its  middle  with  that  vesicle,  but  after  a  time  shows 
its  eventual  division  into  oesophagus,  stomach,  large  and  small  intestines, 
assuming  an  oblique  position  on  the  part  to  be  occupied  by  the  stomach, 
and  then  curving  in  the  region  of  the  intestine.  From  a  part  of  this  tube 


INDICATIONS  OF  CONCEPTION.  533 

the  liver  emerges  as  a  thickened  deposit  of  cells,  into  which  the  wall  of 
the  intestine  bulges  so  as  to  form  a  kind  of  sac,  and  from  this  rudiment 
a  ramified  structure  arises,  which  at  last  recedes  from  its  place  of  origin, 
and  is  connected  with  the  intestine  by  the  hepatic  duct.  The  commence- 
ment of  this  structure  is  about  the  third  week,  but  it  proceeds  with  so 
much  rapidity  that  in  the  third  month  it  nearly  fills  the  abdominal  cav- 
ity. The  functions  of  the  liver  at  this  period  have  already  been  pointed 
out,  the  meconium  it  secretes  being  modified  bile  (page  202).  In  like 
manner,  from  the  digestive  tract,  the  pancreas  and  salivary  glands  orig- 
inate from  masses  of  cells,  ducts  being  formed  by  deliquescence  of  por- 
tions within.  From  the  alimentary  canal,  also  by  budding  and  deliques- 
cence, the  lungs  arise,  their  cavity  communicating  at  first  by  several  aper- 
tures with  the  pharynx.  This  occurs  about  the  sixth  week.  These  organs 
are  gradually  removed  from  the  place  of  origin,  as  in  the  case  of  the  liver. 

The  Wolffian  bodies  are  temporary  urinary  organs,  which  precede  the 
kidneys  and  eventually  disappear.  They  are  of  an  ovoid  The  Wolffian 
shape,  and  consist  of  a  duct  from  which  transverse  canals  todies. 
branch  forth,  the  duct  discharging  into  the  sinus  urogenitalis.  They 
originate  about  the  end  of  the  first  month,  and  commence  to  degenerate 
in  the  third.  In  fishes  they  remain  as  the  permanent  urinary  apparatus. 
The  testes  or  ovaries  arise  from  the  inner  margin  of  the  Wolffian  body, 
the  former  being  guided  into  the  scrotum  by  the  gubernaculum.  This 
descent  commences  between  the  fourth  and  fifth  month,  and  is  completed 
at  birth  or  shortly  after. 

Among  the  indications  that  conception  has  occurred  are  usually  enu- 
merated, stoppage  of  the  menses,  the  placental  murmur,  the  indications  of 
development  of  the  mammary  gland,  its  sense  of  pain  or  ten-  conception, 
derness,  the  color  of  the  areola,  the  turgescence  of  the  areola  and  nipple, 
irritability  of  the  stomach.  Quickening,  as  it  is  termed,  usually  occurs 
about  the  eighteenth  week,  and  parturition  in  the  fortieth,  or  at  the  close 
of  280  days.  With  respect  to  this,  it  is  admitted  that  the  term  may  be 
possibly  .prolonged,  in  very  rare  cases,  by  40  days.  The  French  laws  le- 
gitimatize a  child  born  within  300  days  ;  and  that  such  variations  of  the 
proper  term  may  occur  is  proved  by  observations  made  upon  domestic 
animals,  in  which  the  duration  of  pregnancy  can  be  ascertain-  period  of  ges- 
ed  with  precision.  In  the  cow,  which  has  the  same  period  of  **&<>*• 
gestation  as  the  human  female,  the  shortest  period  hitherto  observed  is 
213  days,  the  longest  336.  The  shortest  period  at  which  human  par- 
turition can  occur,  consistent  with  the  viability  of  the  child,  appears  to 
be  about  23  weeks. 

The  act  of  parturition  in  its  first  stage  is  to  be  referred  to  a  contrac- 
tion of  the  muscular  fibres  of  the  fundus  and  body  of  the  Mechanism  of 
uterus  with  a  synchronous  relaxation  of  those  of  the  cervix,  parturition. 


534  GEMMATION. 

At  a  later  period  the  contraction  of  the  expiratory  muscles  assists.  After 
birth  is  accomplished,  the  mouths  of  the  uterine  vessels  are  closed  through 
the  contraction  of  the  organ,  the  lochial  discharge  carrying  with  it  any 
disintegrated  residues  of  the  deciduous  membrane,  and  also  large  quanti- 
ties of  fat,  derived  probably  from  the  degeneration  of  the  uterine  struc- 
ture itself. 

That  both  parents  are  concerned  in  imparting  characteristics  to  the 
Influence  of  child  there  can  be  no  doubt :  it  is  fully  established  where  they 
both  parents.  are  Of  different  races,  as  white  and  black,  or  white  and  red ; 
and  equally  in  the  case  of  animals,  as  in  mules,  produced  by  the  mix- 
ture of  different  kinds.  It  is  scarcely  necessary  to  remark  that  this  ex- 
tends to  the  communication  of  more  refined  peculiarities,  the  resemblance 
of  countenance,  figure,  gesture,  and  even  mental  qualities,  family  like- 
nesses which  we  daily  observe.  These  impressions  are  of  a  much  more 
profound  character  than  might  at  first  be  supposed,  as  is  proved  by  the 
fact  that  the  third  generation  will  exhibit  peculiarities  belonging  to  its 
progenitors,  though  those  peculiarities  have  not  occurred  in  the  second. 
Even  after  parturition  is  over  there  still  remains  impressed  upon  the  fe- 
male a  definite  change :  this  is  illustrated  by  the  well-known  case  of  a 
mare  which  had  borne  a  colt  by  a  quagga,  her  subsequent  colts  by  horses 
being  distinctly  marked  like  the  first ;  and  in  the  human  female  cases 
are  of  common  occurrence  in  which  the  offspring  of  a  widow,  who  has 
been  married  a  second  time,  resemble  her  first  husband.  Marriage  pro- 
duces in  this  respect  a  permanent  change  in  the  female,  a  constitutional 
impression  not  disappearing  in  any  length  of  time,  the  influence  of  the 
first  husband  reappearing  in  the  children  of  a  subsequent  contract. 

2D.    GEMMATION. 

The  ascending  axis  of  a  plant  is  terminated  by  a  differentiating  part, 
Gemmation  of  surrounded  by  protecting  structures.  From  this,  as  growth 
plants  and  ani-  takes  place,  leaves  or  their  modifications  are  produced.  This 
differentiating  part  is  a  bud.  In  like  manner  may.be  found 
in  the  axils  of  leaves  similar  buds,  which  pass  by  development  into 
branches,  but  sooner  or  later  the  terminal  buds  are  checked  in  their  lon- 
gitudinal increase,  and  the  parts  to  which  they  would  have  given  origin 
Fig.  265.  spirally  being  compressed  into  circles,  a  flower  arises, 

and  further  development  ceases,  the  reproductive  phase 
being  now  assumed. 

Among  the  lower  animals  propagation  by  buds  is 
also  observed.     Thus  the  hydra  exhibits  this  manner 
of  increase,  as  seen  in  Fig.  265 ;  and  even  upon  the 
buds  thus  produced,  other  buds,  of  a  second  order  or 
Hydra  budding.        generation,  are  found. 


METHODS   OF   GRAFTING.  535 

Propagation  through  the  agency  of  buds  is  termed  gemmation.  It 
may  be  accomplished  either  by  the  natural  or  artificial  separation  of  the 
buds  from  the  parent  stock.  Thus,  in  the  hydra,  the  buds  may  spon- 
taneously be  separated  from  the  parent,  and  thereby  give  rise  to  free  in- 
dividuals, or  they  may  be  purposely  cut  off  with  the  same  result.  In 
the  case  of  plants,  artificial  separation  is  constantly  resorted  to,  as  in  the 
various  methods  of  budding  and  grafting  employed  by  horticulturists  for 
obtaining  the  finer  varieties  of  flowers  or  fruits.  It  consists  Methods  of 
essentially  in  placing  a  bud  of  the  plant  which  it  is  desired  to  grafting- 
propagate  upon  a  stock  of  a  different  kind,  in  such  a  way  that,  as  devel- 
opment of  the  bud  or  scion  takes  place,  union  or  incorporation  with  the 
stock  shall  occur.  There  are  many  different  ways  in  which  grafting  may 
be  performed ;  they  all  depend  for  their  success,  however,  upon  causing 
the  alburnum  of  the  scion  to  coincide  with  that  of  the  stock,  so  that  the 
vessels  of  the  former  may  receive  the  sap  arising  from  those  of  the  latter. 
When  the  parts  are  thus  adjusted,  they  are  to  be  retained  in  their  posi- 
tion by  bandages  or  other  suitable  means,  and  protected  from  the  air  and 
rain  by  means  of  clay  or  wax.  The  most  suitable  time  for  this  opera- 
tion is  in  the  spring,  just  previous  to  the  rising  of  the  sap. 

There  are  certain  limits  within  which  the  operation  of  grafting  must 
be  performed.     The  stock  and  the  scion  must  be  nearly  re-  Limits  of  gem- 
lated  to  each  other.    If  species  of  different  natural  orders  be  mation' 
grafted  they  will  not  take,  but  the  species  of  the  same  genus  may. 

If  in  this  manner  we  take  a  bud,  and  graft  it  on  a  stock  of  an  allied 
kind,  it  will  continue  to  grow  and  develop  in  the  same  man-  Nature  of 
ner  that  it  might  have  done  without  detachment  from  the  propagation 
parent  plant,  and  in  the  same  manner  from  the  new  plant  that. bygem 
has  thus  arisen,  by  a  repetition  of  the  process,  plant  after  plant,  for  many 
generations,  can  be  secured.  Experience  has  taught  us  that,  whatever 
might  have  been  the  peculiarities  of  the  original  from  which  the  first  bud 
was  taken,  those  peculiarities,  whether  of  odor,  taste,  color,  or  shape,  will 
reappear  in  the  product ;  but  experience  has  also  taught  us  that  thereds 
a  limit  beyond  which  these  repetitions  can  not  be  conducted.  The  val- 
ued fruits  and  flowers  of  the  old  times  have  thus  disappeared.  Propaga- 
tion by  gemmation  is  therefore  considered  as  tending  to  exhaust  the  orig- 
inal plastic  power.  But  it  is  to  be  remarked  that,  if  from  these  artificial 
growths  seeds  be  taken  and  caused  to  germinate,  the  plants  so  arising  no 
longer  present  the  special,  and,  perhaps,  valued  peculiarity,  but  in  many 
instances  run  back  at  once  to  the  original  and  wild  stock. 

We  are  apt  to  attach  to  propagation  by  gemmation  more  importance 
than  it  really  deserves  in  a  philosophical  point  of  view  when  it  thus  ap- 
pears to  have  given  rise  to  new  and  successive  generations  of  individuals. 
But,  after  all,  wherein  does  it  differ  essentially  from  what  goes  on  natur- 


536  SPONTANEOUS   GEMMATION. 

ally  ?  The  manner  of  extension  of  any  given  plant  is  by  bud  after  bud 
in  succession,  either  terminal  or  axillary ;  but  this  extension  does  not  go 
on  indefinitely ;  it  reaches  a  limit  both  as  respects  size  and  duration. 
We  never  notice  in  the  development  of  a  bud  which  remains  attached  to 
its  parent  stock  the  spontaneous  appearance  of  novel  qualities.  The 
flowers  and  fruits  are  like  all  the  others  upon  the  same  plant.  If  such 
a  bud,  then,  removed  from  its  parent  seat,  be  permitted,  under  favorable 
conditions,  to  grow  elsewhere,  it  might  be  expected,  as  is  actually  the  case, 
that  it  would  go  on  in  its  development  without  exhibiting  any  alterations. 

Essentially  of  an  exhausting  nature,  reproduction  by  gemmation  is 
limited.  It  can  only  be  repeated  a  definite  number  of  times.  At  the 
most,  all  that  we  do  in  this  artificial  process  is  to  obtain  a  part  of  an  old 
individual  under  a  new  and  isolated  form.  We  thereby  relieve  such 
new  growth  from  the  chance  of  those  accidents  which  may  befall  the 
original  stock ;  but  both  for  the  one  and  for  the  other  there  is  a  definite 
term  of  life.  When  that  term  is  approached,  though  we  may  take  sci- 
ons or  buds,  and  treat  them  with  every  care  in  the  usual  operation  of 
grafting  or  budding,  the  operation  will  fail. 

There  is  a  certain  analogy  between  this  incorporation  of  the  parts  of 
different  plants  and  the  so-called  grafting  or  Taliacotian  operations  which 
are  sometimes  performed  on  the  parts  of  animals,  as  the  transplantation 
of  the  spur  of  one  bird  on  the  top  of  the  comb  of  another,  or  many  of  the 
plastic  operations  of  surgery ;  but  these  parts  do  not  necessarily  perish 
in  the  manner  which  has  been  indicated  by  Butler  in  his  Hudibras. 

Propagation  by  gemmation  and  reproduction  by  generation  are,  in 
many  instances  in  the  animal  series,  resorted  to  alternately  for  the  con- 
tinuation of  the  race.  Thus,  during  the  summer  season,  propagation  by 
gemmation  may  serve  to  increase  the  number  of  a  given  kind,  but  if  these 
should  be  unable  to  maintain  themselves  during  the  cold  of  winter,  the 
race  would  inevitably  become  extinct,  unless  reproduction  by  ova  were 
resorted  to ;  for  though  the  developed  animal  may  not  be  able  to  with- 
Influence  of  stand  the  decline  of  temperature,  the  ova  may.  Thus,  in 
spontaneous011  a  hydra,  propagation  by  gemmation  continues  until  the  ex- 
gemmation,  ternal  temperature  lowers  to  a  certain  degree,  and  that  at 
once  brings  on  a  reversion  to  the  other  process.  The  same  thing  has 
been  observed  in  the  case  of  the  aphis,  which  multiplies  by  gemmation 
until  there  is  a  reduction  of  temperature,  and  then  it  multiplies  by  gener- 
ation. We  have  already  dwelt  at  length  on  the  control  which  external 
circumstances  have  over  development;  it  is,  therefore,  no  more  than  might 
be  expected  that  they  should,  in  like  manner,  determine  the  processes  of 
propagation  and  reproduction. 

Gemmation  occurs  only  in  a  very  doubtful  way  and  under  special  cir- 
cumstances among  the  more  advanced  members  of  the  animal  series.  In 


ALTERNATION  OF  GENERATIONS.  537 

man,  there  is  reason  to  suppose  that  gemmation  can  only  take  place  in 
the  earliest  periods  of  existence,  perhaps  at  the  epoch  of  the  formation  of 
the  mulberry  mass.  Upon  this  principle  an  explanation  of  the  occur- 
rence of  double  monsters  has  been  given. 

3D.   ALTERNATION  OP   GENERATIONS. 

It  has  been  already  explained  that  by  this  phrase  is  meant  that  a  pa- 
rent plant  or  animal  will  give  origin  to  a  form  wholly  unlike  Alternate  em 
itself,  and  this  form,  perhaps  after  the  lapse  of  years,  will  mation  and 
give  origin  to  another  unlike  itself,  but  similar  to  the  original  Seneratlon- 
progenitor.  Thus  the  Salpse  present  themselves  under  two  different  as- 
pects, the  solitary  and  the  aggregated,  the  latter  being  produced  from  the 
former  by  being  Thudded  off  in  an  internal  stolon,  the  individuals  being 
united  to  one  another  in  an  aggregation  or  chain  after  they  have  been 
separated  from  the  parent.  These  aggregated  salpas  alone  have  sexual 
organs  and  produce  ova.  From  each  ovum  a  solitary  salpa  arises,  which 
repeats  the  process  described  again.  The  solitary  salpa,  therefore,  mul- 
tiplies by  gemmation,  the  aggregate  by  generation.  Nor  is  this  process 
confined  to  animals ;  it  is  also  observed  in  the  case  of  plants.  Thus, 
in  ferns,  the  spore  produces  the  prothallium,  which  becomes  a  distinct  or- 
ganism, separated  from  its  parent,  and  carrying  on  its  nutritive  processes 
independently  for  itself.  From  it  arises  by  generation  a  fern  like  the 
original,  which,  like  it,  by  gemmation,  produces  prothallia,  but  never 
directly  produces  a  fern.  Therefore  between  each  fern  and  its  descend- 
ant a  prothallium  intervenes,  the  prothallium  arising  by  gemmation  from 
the  fern,  and  a  fern  arising  by  generation  from  the  prothallium. 

After  a  careful  examination  of  Steenstrup's  doctrine  of  alternations  of 
generation,  Dr..  Carpenter  concludes  that  it  can  not  be  re-  ,,    , 

0  L  Explanation 

ceived  in  the  form  originally  presented,  since  we  should  re-  of  alternations 
gard  a  generation  as  embracing  the  entire  product  from  gen-  of  seneratlon- 
erative  act  to  act.  Indeed,  the  intermediate  forms  are  often  nothing 
more  than  sexual  organs,  furnished  or  not  with  an  apparatus  of  locomo- 
tion, or,  in  "the  more  complicated  cases,  having  a  mechanism  of  nutrition 
attached  sufficient  for  their  purpose.  The  correctness  of  this  interpreta- 
tion may  be  illustrated  by  such  cases  as  the  development  of  medusa  buds, 
which,  being  first  attached  to  the  parent,  gradually  exhibit  the  formation 
of  an  independent  digestive  apparatus,  and  when  this  has  reached  a  cer- 
tain degree  of  perfection,  they  are  separated  and  swim  off,  generative  or- 
gans then  arising  in  these  buds  by  which  true  ova  are  formed.  In  the 
Sentularidas  buds  are  developed  in  ovarian  capsules,  and  these  reproduce 
in  their  turn  ova  by  generation.  The  rate  at  which  gemmation  goes  on 
in  many  of  these  instances  is  obviously  connected  with  physical  condi- 
tions, more  particularly  the  degree  of  temperature  and  the  supply  of  food. 


538  GROWTH   OF  MAN. 

The  fact  of  the  apparent  dissimilarity  between  the  product  of  gemma- 
tion and  the  product  of  generation  ceases  to  have  any  force  as  soon  as 
we  consider  the  former  in  the  attitude  which  it  really  ought  to  occupy, 
as  not  constituting  a  distinct  individual,  but  merely  a  part,  a  derivative, 
or  an  appendix  of  the  product  of  generation  ;  and  this  view  of  Dr.  Car- 
penter's seems,  therefore,  to  be  the  proper  interpretation  of  the  whole  case. 


CHAPTER  V. 

THE  GROWTH  OF  MAN. 

Infancy. —  Weight  and  Size  of  the  Infant. —  Weight  and  Size  at  subsequent  Periods. — Develop- 
ment of  the  Intellect. — Maturity  of  Man. —  Tendency  to  Crime. — Maxima  of  Physical  and  Men- 
tal Strength. 

Mental  and  Physical  Decline. — Mortality  at  different  Periods  of  Life. —  Comparative  Structure, 
Functions,  and  Mortality  of  the  two  Sexes. 

Artificial  Epochs  of  Life. — Gradual  Change  in  the  Mental  Qualities. — Independent  Existence  of 
the  Soul. 

IN  the  last  chapter  the  successive  stages  of  embryonic  development 
were  described.  It  was  shown  that  at  one  period  nutrition  is  solely  at 
the  expense  of  the  yolk  of  the  ovum,  which  is  appropriated,  by  a  simple 
surface-imbibition ;  and  that  this,  in  due  time,  is  succeeded  by  what  has 
been  designated  tuft  nutrition.  At  a  later  period,  this  mode,  in  its  turn, 
is  replaced  by  another,  depending  on  a  vascular  arrangement,  the  pla- 
infancy  of  centa.  For  a  considerable  period  after  birth  a  fourth  system  is 
man.  relied  on,  nourishment  by  milk ;  and  it  is  only  by  degrees,  when 
the  necessary  changes  have  been  made  in  the  digestive  mechanism,  the 
teeth  being  cut,  that  the  final  mode  of  nutrition  is  assumed.  Even  after 
this  the  human  infant  leads  a  dependent  life,  because  of  its  own  weak- 
ness and  imbecility,  irrespectively  of  any  peculiarities  of  our  social  state. 
So  far,  therefore,  from  man  not  exhibiting  those  metamorphoses  which 
are  undergone  by  the  lower  members  of  the  animal  series,  he  of  all  dis- 
plays them  in  the  most  marked  way,  for  they  do  not  cease  at  the  period 
of  birth,  but  reach  through  many  subsequent  years — a  gradual  develop- 
ment of  the  body,  attended  by  a  gradual  change  in  the  manifestations  of 
the  mind. 

At  birth,  the  human  infant  is  the  very  representative  of  weakness  and 
imbecility.  Though,  unlike  many  other  mammals,  it  opens  its  eyes  at 
once,  it  exhibits  no  token  of  visual  perceptions ;  though  it  may  be  sub- 
jected to  sounds  or  noises  of  various  kinds,  it  takes  no  notice  whatever 
of  them.  This  condition  of  inertness  is  followed  by  a  condition  of  con- 
fused sensation,  which  by  degrees  is  succeeded  by  a  capability  of  ap- 


THE  TEETH.  539 

predating  special  ideas.  Buffon  has  very  truly  said  that  the  earliest 
period  of  conscious  existence  is  a  scene  of  pain,  the  life  of  the  infant  "be- 
ing divided  between  sleep  and  crying ;  from  its  slumbers  it  is  awakened 
only  by  the  pains  of  hunger ;  nor  is  it  until  after  the  lapse  of  many  days, 
or  even  weeks,  that  the  first  smile  is  seen.  It  is  too  feeble  to  turn  from 
side  to  side,  but  remains  in  the  position  in  which  it  was  placed.  Its 
skin,  which  at  birth  was  covered  over  with  a  whitish  incrustation,  the 
vernix  caseosa,  becomes  reddish,  the  depth  of  this  tint,  however,  shortly 
passing  away.  At  this  period,  moreover,  life  is  purely  vegetative,  the  in- 
fant feeding  and  sleeping.  The  biliary  matter,  meconium,  which  had  ac- 
cumulated in  its  intestine  during  foetal  life,  is  discharged  in  the  course  of 
a  day  or  so  after  birth,  and  the  digestive  apparatus  enters  on  its  functions 
with  activity. 

It  is  said  that  the  infant  smiles  soon  after  it  is  forty  days  old ;  though 
it  can  cry  it  can  not  shed  tears.  Before  long  it  gives  indications  of  its 
satisfactions  and  dislikes.  The  power  of  moving  in  an  erect  posture  is 
gained  by  it  in  the  course  of  a  year,  and  by  the  close  of  that  time  it  can 
masticate.  Of  its  teeth,  the  central  incisors  appear  about  the 
seventh  month,  those  of  the  lower  jaw  first ;  the  lateral  incisors 
about  the  eight  or  tenth,  the  anterior  molars  about  the  twelfth,  and  the  ca- 
nines about  the  eighteenth,  the  posterior  molars  being  cut  between  that 
time  and  three  years.  The  average  date  of  the  appearance  of  the  perma- 
nent teeth  is,  the  front  molars  about  the  seventh  year ;  middle  incisors, 
eighth ;  lateral  incisors,  ninth ;  anterior  bicuspids,  tenth ;  second  bicuspids, 
eleventh ;  canines,  twelfth  to  thirteenth ;  second  molars,  twelfth  to  four- 
teenth; and  the  last  molars  from  the  seventeenth  to  the  twenty-firs, t  year. 

The  power  of  articulate  speech  is  displayed  within  twelve  or  fifteen 
months,  some  letters  being  more  easily  gained  than  others ;  among 
themareA,B,P,M. 

From  henceforth  the  mind  emerges  with  rapidity  from  the  confusion 
of  a  multitude  of  impressions,  and  learns  to  concentrate  itself  Concentration 
at  pleasure  upon  one.     This  capability  of  mental  abstraction  of  the  atten- 
is  a  process  of  specialization,  and  is  a  manifestation  of  the  tlon' 
law  of  Von  Bar.    The  intellectual  difference  which  we  eventually  observe 
between  one  man  and  another  is,  to  no  inconsiderable  degree,  dependent 
upon  such  an  ability  of  concentrating  thought.     He  who  conceives  of  a 
thing  distinctly  is  very  likely  to  express -himself  of  it  clearly. 

Throughout  infancy  and  childhood,  the  features,  and  even  the  gestures, 
indicate  the  profound  constitutional  changes  which  are  going  on.  The 
countenance,  instead  of  expressing  pleasure  and  pain  in  the  aggregate  by 
smiling  or  crying,  as  was  the  case  at  first,  gains  the  faculty  of  represent- 
ing every  grade  of  feeling.  Long  before  maturity  is  reached  we  read 
without  difficulty  the  thoughts  which  are  passing  in  the  mind  from  the 


540  MAXIMUM  AND  MINIMUM  OF  HEIGHT. 

movements  of  the  lip  or  the  eye,  and  the  painter  can  express  every  shade 
of  feeling,  and  every  emotion,  by  the  mere  configuration  of  the  outward 
form. 

The  monthly  growth  of  the  foetus  for  six  months  before  birth  is  es- 
Mean  length  tablished  at  two  inches.  At  birth,  the  mean  length  of  boys 
of  the  infant.  js  jgi.  jncneS)  and  of  girls  18 £  inches,  the  former  being  there- 
fore a  little  the  longer. 

At  sixteen  or  seventeen  years  the  growth  of  girls  is  relatively  as  much 
Growth  of  boys  advanced  as  that  of  youths  of  eighteen  or  nineteen.  For 
and  girls.  the  most  part,  the  inhabitants  of  towns  are  taller  than  those 
of  the  country.  The  full  height  is  not  reached,  in  some  instances,  until 
twenty-five  years  ^  in  very  warm  and  very  cold  climates  it  is  more  quick- 
ly attained.  The  recumbent  position  is  regarded  as  being  favorable  to 
growth,  and,  influenced  by  his  own  weight,  an  individual  is  shorter  in 
the  evening  than  when  he  first  rises  from  bed  in  the  morning. 

With  regard  to  the  rate  of  growth,  it  may  be  observed  that  it  is  most 
rapid  immediately  after  birth,  and  continually  diminishes  until  about  five 
years,  the  epoch  of  maximum  of  probable  life.  It  then  remains  equable 
to  about  sixteen  years,  the  annual  growth  being  2-^  inches.  After  pu- 
berty it  declines,  being,  from  sixteen  to  seventeen  years,  1J  inches,  and 
during  the  next  two  1  inch  only.  The  annual  increment  relatively  to 
the  height  then  attained  continually  diminishes  from  birth.  The  foetus 
grows  as  much  in  length  in  a  month  as  the  child  from  6  to  16  years 
does  in  a  year.  The  limits  of  growth  of  the  two  sexes  are  unequal,  be- 
cause women  are  smaller  than  men,  terminate  their  growth  sooner,  and 
annualjy  grow  less.  Individuals  in  affluent  circumstances  may  often 
surpass  the  standard  height,  but  misery  and  fatigue  are  liable  to  produce 
the  opposite  effect.  Longevity  is  generally  less  for  persons  of  great 
height. 

As  to  the  maximum  and  minimum  of  height,  it  may  be  remarked  that 
Maximum  and  Frederick  the  Great  had  a  Swedish  body-guard  whose  height 
minimum  was  eight  feet  three  inches ;  and,  on  the  other  hand,  Birch 
ian'  states  that  there  was  an  individual,  37  years  old,  whose 
height  was  sixteen  inches.  In  view  of  these  and  other  such  facts, 
Quetelet  fixes  on  8  feet  3  inches  as  the  maximum,  and  1  foot  5  inches 
as  the  minimum  of  height ;  he  gives  as  the  mean  5  feet  4  inches.  Half 
the  men  of  France,  at  the  age  of  conscription,  are  between  5  feet  2  inches 
and  5  feet  6  inches,  but  the  wars  incident  on  the  great  Revolution  made 
a  permanent  impression  on  the  French  in  this  respect  by  lowering  the 
standard  through  the  consumption  of  the  taller  men.  M.  Quetelet  more- 
over remarks,  that  in  ten  millions  of  men  there  is  but  one  more  than  6 
feet  8  inches,  and  one  less  than  4  feet.  There  is  reason,  however,  to  be- 
lieve that  this  statement  will  not  hold  good  of  America. 


WEIGHT  AND  HEIGHT.  541 

As  regards  weight,  new-born  boys  are  heavier  than  girls.  An  average 
taken  from  20,000  gives  6£  Ibs.  as  the  weight  at  birth;  the  weight  of 
maxima  and  minima  have  been  10  J  Ibs.  and  2  J  Ibs.  For  about  infants. 
a  week  after  birth  the  weight  diminishes,  owing  to  the  effect  of  aerial 
respiration.  The  difference  in  weight  between  the  two  sexes  gradually 
diminishes  until  about  the  twelfth  year,  when  an  equality  is  reached. 
The  maximum  w*eight  is  attained  about  40,  and  as  60  is  ap-  We-  tt  at  dif_ 
proached  a  diminution  is  perceived,  which  reaches  12  Ibs.  ferent  periods 
at  about  80  years,  the  stature  likewise  correspondingly  di-  ° 
minishing  by  about  2|  inches ;  the  female  reaches  her  maximum  weight 
somewhat  later,  at  about  50  years.  The  extreme  limits  of  weight  in 
men  are  108  Ibs.  and  216  Ibs. ;  in  women,  87J  Ibs.  and  206£  Ibs.  The 
mean  weight  at  nineteen  is  nearly  that  of  old  age  in  both  sexes.  At  full 
development  the  male  and  female  weigh  almost  exactly  20  times  as  much 
as  at  birth.  In  the  first  year  the  infant  of  both  sexes  triples  its  weight. 
It  requires  six  years  more  to  double  that,  and  thirteen  to  quadruple  it. 
Immediately  after  puberty  both  sexes  have  half  their  ultimate  weight. 
Between  the  ages  of  25  and  40  the  mean  weight  of  the  male  is  136J  Ibs., 
and  of  the  female  120f  Ibs. 

With  respect  to  the  relation  between  weight  and  height,  if  man  increased 
equally  in  all  his  dimensions,  the  weight  would  be  as  the  cube  Eelation  of 
of  the  height ;  but  since  this  is  not  so,  development  taking  place  height  and 
unequally,  the  proportion  is  not  observed,  and  it  is  found  that  weig  fc* 
from  the  end  of  the  first  year  to  puberty  the  weights  are  as  the  squares 
of  the  heights.  M.  Quetelet  gives  as  an  approximate  rule  that  during 
development  the  squares  of  the  weights  at  different  ages  are  as  the  fifth 
power  of  the  heights,  the  transverse  growth  being  less  than  the  growth 
in  height.  The  mean  weight  of  a  male,  without  reference  to  age,  is  103f 
Ibs. ;  of  a  female,  93f .  A  similar  calculation  for  the  population  of  the 
United  States  as  that  which  has  been  given  by  this  philosopher  for  Brus- 
sels would  give  for  the  total  weight  of  all  Americans  two  thousand  six 
hundred  and  thirteen  millions  of  pounds. 

The  weight  of  an  individual,  considered  without  reference  to  age  or 
sex,  is  98J  Ibs. 

From  birth  until  puberty  the  mode  of  life  is  essentially  vegetative,  all 
the  instincts  having  relation  to  the  individual  and  corporeal  development. 
Except  through  the  intervention  of  education,  the  desires  of  the  child  are 
chiefly  directed  to  the  pleasures  of  mere  vegetative  existence,  eating  and 
drinking ;  and  this,  in  savage  races,  is  witnessed  in  a  much  more  mark- 
ed manner  than  in  those  that  are  civilized,  in  whom  the  manner  of  life  is 
affected  through  the  intervention  of  parental  care.  In  this  particular  it 
may  be  remarked  that  maternal  love  is  divisible  into  an  in-  Maternal  love 
stinctive  and  a  moral  affection,  the  former  of  a  lower  and  of  two  kinds. 


542  MATURITY  OF  MAN. 

more  animal  kind,  the  latter  of  a  higher  and  intellectual ;  the  former  lim- 
ited to  the  period  of  infantile  helplessness  and  dependence,  and  succeed- 
ed by  the  latter  as  maturer  years  are  attained.  In  savage  races,  howev- 
er, instinctive  affection  seems  alone  to  exist,  and  the  intensity  of  moral 
affection  is,  to  a  certain  extent,  a  measure  of  civilization.  Throughout 
Character  of  t^ie  ^rst  ^teen  years  of  life,  with  the  gradual  development 
the  life  of  chil-  of  the  body  there  is  also  a  steady  intellectual  progress,  the 
dren'  gains  of  which  seem  to  be  greatest  at  the  earlier  periods,  and 

less  and  less  marked  as  maturity  is  approached.  When  we  recall  the 
wonderful  advance  accomplished  in  the  first  years,  embracing  the  acqui- 
sition of  speech,  and  a  knowledge  of  the  nature  and  qualities  of  a  thou- 
sand surrounding  objects,  we  might  be  led  to  suppose  that  our  mental 
acquisitions  decline  with  the  progress  of  life ;  but  this  is  altogether  de- 
ceptive ;  for,  though  the  acquirements  of  later  years  be  less  obvious,  they 
are  none  the  less  important  and  none  the  less  profound. 

Through  the  successive  changes  to  which  allusion  has  now  been  made, 
The  maturity  each  of  which  is  a  strict  metamorphosis,  and  each  of  which, 
of  man.  w^n  its  special  structures,  has  its  special  functions,  man  at  last 
reaches  maturity.  In  some  cases,  as  we  have  seen,  the  stature  contin- 
ues increasing  until  after  the  twenty-fifth  year,  and  throughout  the  whole 
mature  period,  even  after  what  has  been  termed  the  meridian  of  life  is 
gained,  the  weight  also  becomes  greater.  This  increase  of  weight,  how- 
ever, has  not  so  much  a  relation  to  the  muscular  as  to  the  respiratory  sys- 
tem, for  the  former  reaches  its  perfection  at  a  much  earlier  date,  the  in- 
creasing development  of  the  middle  period  of  life  being  due  to  a  continued 
tendency  to  the  accumulation  of  fat.  At  this  period,  moreover,  the  object 
of  life  has  undergone  an  entire  change ;  the  vegetative  propensity,  or  that 
for  the  exclusive  development  of  the  individual,  has  declined  in  prom- 
inence, and  the  reproductive  has  been  assumed.  With  this  there  have 
been  awakened  new  sentiments  and  new  emotions,  affording  still  another 
corroborative  proof  of  the  connection  of  mental  habitudes  and  structural 
condition.  The  psychical  powers  are  now  advancing  toward  maturity, 
an  advance  which  they  continue  to  make  until  about  the  fiftieth  year. 
Throughout  this  whole  period,  and  even  at  this  extreme  date,  we  still 
notice  how  much  intellectual  capacity  is  connected  with  the  perfection  of 
corporeal  development.  It  needs  but  a  little  experience  for  us  to  de- 
termine at  a  glance  the  intelligent  from  the  obtuse,  and  to  read  even  the 
minor  shades  of  character  in  the  aspect  of  the  face.  Without  being 
aware  of  it,  we  are  constantly  putting  into  requisition  the  principles  of 
phrenology  and  physiognomy,  and  drawing  conclusions  respecting  char- 
acter to  a  certain  degree  correct,  from  the  expression  of  the  eyes,  the  lin- 
eaments of  the  countenance,  or  the  configuration  of  the  head. 

The  actions  of  man  are  closely  connected  with  the  physical  and  moral 


TENDENCY  TO   CRIME.  543 

circumstances  under  which  he  is  placed.  The  greatest  nura-  The  tendency 
ber  of  crimes  against  persons  and  property  is  among  the  inhab-  to  crime  in 
itants  of  river-banks.  The  period  of  the  maximum  of  crimes  n 
against  persons  coincides  with  that  which  is  the  minimum  against  prop- 
erty, and  is  the  summer  season.  As  respects  each  individual,  his  tend- 
ency to  crime  is  at  first  against  property,  and  this  reaches  its  maximum 
at  about  25  years  of  age,  whereas  the  tendency  to  crime  against  persons 
commences  later  than  that  against  property,  and  increases  with  the  in- 
crease of  strength.  In  crime,  man,  as  he  grows  older,  substitutes  strata- 
gem for  force.  If  brought  up  in  a  liberal  profession,  his  tendency  in 
crime  is  against  persons,  but  that  of  the  workman  is  against  property. 
Elementary  instruction,  so  far  as  reading  and  writing  go,  does  not  lead 
to  the  diminution,  but  rather  to  the  increase  of  crime :  a  very  Prejudicial  efL 
important  conclusion,  more  particularly  in  the  United  States,  feet  of  low  ed- 
in  many  portions  of  which  this  kind  of  education  is  chiefly 
patronized  by  government,  to  the  exclusion,  to  a  certain  extent,  of  that 
which  is  of  a  higher  grade,  and  which  serves  to  correct  this  important 
defect..  Moreover,  superficial  education  makes  the  mind  a  ready  recep- 
tacle for  every  kind  of  imposture,  and  has  been  the  cause  of  the  rapid 
spread  of  many  modern  delusions,  such  as  spiritualism  and  homoeopathy. 
As  regards  women,  their  tendency  to  crime,  when  compared  with  that 
of  men,  is  as  23  to  100 ;  at  least  this  is  the  case  in  France.  _ 

Ine  tendency 

Their  tendency  for  the  perpetration  of  crimes  against  persons  to  crime  in 
is  less  than  that  for  crimes  against  property  in  the  proper-  ^ 
tion  of  16  to  26.  It  is  interesting  to  observe  that  the  physical  force  of 
woman,  as  compared  with  that  of  man,  is  also  as  16  to  26.  From  such 
considerations,  it  may  therefore,  perhaps,  be  concluded  that  the  morality 
of  women  is  about  the  same  as  that  of  men,  their  physical  feebleness  and 
modesty  being  taken  into  account.  In  woman,  the  maximum  tendency 
for  crime  occurs  at  about  30  years,  but  then  she  relinquishes  that  dispo- 
sition sooner  than  man.  Her  tendency  to  theft,  however,  begins  early, 
and  lasts  through  life.  When  she  desires  to  commit  murder,  she  em- 
ploys, by  preference,  poison.  In  this  may  be  discerned  the  influence  of 
her  constitutional  element,  physical  feebleness.  Timid  at  explosions  and 
at  the  sight  of  blood,  if  driven  to  the  extremity  of  self-destruction,  she 
instinctively  resorts  to  drowning.  Women,  like  men,  who  are  the  res- 
idents of  towns,  are  much  less  moral  than  those  who  live  in  the  country. 
This  may  be  inferred  from  such  facts  as  that  the  annual  percentage  of 
still-births  occurring  in  the  former  is  very  near  double  of  that  occurring 
in  the  latter  case ;  and  though  this  may  be,  to  a  certain  extent,  connect- 
ed with  the  fashionable  restraints  of  clothing  and  social  dissipations,  it 
is  far  more  due  to  female  depravity.  The  illegitimate  births  of  towns 
compared  with  those  of  the  country  are  as  23  to  7.  Among  the  still- 


544  MAXIMA   OP   STRENGTH. 

"born,  the  illegitimates  are  to  the  legitimates  as  5  to  3.  In  the  city  of 
Berlin,  the  illegitimate  still-births  are  to  the  legitimate  in  as  high  a  pro- 
portion as  3  to  1. 

The  passions  of  man  are  gratified  in  a  manner  that  seems  to  be  inde^ 
pendent  of  religious  profession.  The  open  dissoluteness  of  one  country- 
is  counterpoised  by  the  secret  crime  of  another.  Protestant  England 
and  Catholic  France  exhibit  a  striking  illustration.  In  the  former,  in 
1845,  the  number  of  illegitimates  was  70  per  thousand  of  the  whole  num- 
ber of  children  born.  In  France  it  was  about  71. 

During  the  process  of  the  development  of  the  intellect  of  man,  various 
Succession  of  Psyc^cal  persuasions  in  succession  arise,  which  are  frequent- 
psychical  per-  ly  imputed  to  education  or  tradition,  but  of  which  the  origin 
is  undoubtedly  to  be  traced  to  the  organization.  Those  gen- 
eral ideas  that  are  found  all  over  the  world,  among  all  races  of  mankind, 
whatever  may  be  the  climate  in  which  they  live,  their  social  condition, 
or  religious  opinions — ideas  of  what  is  good  and  evil,  of  virtue,  of  the 
efficacy  of  penance  and  of  prayer,  of  rewards  and  punishments,  and  of 
another  world :  these,  from  the  uniformity  of  their  existence  in  all  ages 
and  in  all  places,  must  be  imputed  to  the  stamp  that  has  been  put  upon 
our  cerebral  organization.  In  the  same  light  we  must  view,  as  Dr.  Prich- 
ard  has  said,  the  delusions  and  fictions  which  are  universal,  such  as 
ghosts  and  genii,  giants  and  pigmies.  Universal  opinions  are  not  the 
result  of  accident,  nor  always  of  tradition.  They  are  often  creations  of 
the  mind,  arising  from  peculiarities  of  its  constitution. 

Arrived  at  maturity,  the  system  of  man  commences  at  once  to  decline, 
Successive  max-  the  epochs  of  the  maximum  of  physical  and  mental  strength 
and  mental S1<  l  not»  however,  coinciding ;  that  for  the  former  occurring  at 
strength.  about  the  25th  year,  as  previously  remarked,  but  that  for 

the  latter  not  until  between  the  45th  and  50th  year.  At  this  period, 
when  the  powers  of  imagination  and  reason  have  reached  their  highest 
degree,  the  liability  to  mental  alienation  and  insanity  is  also  at  its  max- 
Order  of  men-  imum<  Somewhat  later,  the  physical  system  plainly  be- 
tai  and  physi-  trays  that  it  is  pursuing  its  downward  course,  retracing  the 
steps  through  which  it  passed  forward  to  development.  Soon 
there  is  an  evident  decrease  of  weight,  the  nutritive  operations  being  no 
longer  able  to  repair  the  waste  of  the  body.  There  is  also  a  diminution 
of  the  height.  This  corporeal  decay  is  the  signal  for  a  depression  of  the 
mental  powers,  the  first  which  begins  to  yield  being  probably  that  of  con- 
centrating or  abstracting  the  thought.  As  years  pass  on,  external  im- 
pressions exert  a  diminished  influence,  and  he  who  at  an  earlier  period 
reached  the  meaning  of  things,  as  it  were,  almost  by  intuition,  now  casts 
his  eyes  over  page  after  page  without  an  idea  being  communicated  to  his 
mind.  The  old  man  querulously  complains  that  he  reads  his  book,  but 


LONGEVITY.  545 

does  not  understand  what  it  means.  With  this  failure  of  per-  Extreme  old 
ception  the  powers  of  memory  decline,  recent  events  fading  ase- 
away  first,  "but  those  of  early  life  being  recollected  last.  The  present  no 
longer  possesses  an  interest,  for  the  brain  is  less  capable  of  receiving  any 
new  impressions.  One  after  another,  the  organs  of  sense  fail  to  discharge 
their  functions ;  the  sight  becomes  misty,  the  hearing  dull ;  there  is  an 
indisposition  for  exertion,  a  desire  for  repose.  The  white-bearded  pa- 
triarch of  a  hundred  years  sits  quietly  by  the  fireside,  resting  his  hands 
on  the  top  of  his  staff. 

Instances  of  Longevity. 

Yean. 

Attila 124 

Margaret  Patten 137 

The  Countess  of  Desmond 145                   • 

Thomas  Parr 152 

Thomas  Damme 154 

John  Kovin  >  172 

His  wife....  > .-. 164 

Peter  Torton 185 

The  mortality  of  towns  is  greater  than  that  of  the  country.     As  we 
advance  from  the  midst  of  the  temperate  region  toward  the   ij0cai  raor. 
equator  or  toward  the  poles,  it  also  increases :   thus,  in  the   tali<y- 
northern  portions  of  Europe,  the  annual  mortality  is  as  1  to  41 ;  that  of 
Central  Europe,  1  to  40^ ;  that  of  Southern  Europe,  1  to  33^.     Con- 
sidered as  respects  different  periods  of  life,  the  rate  of  mor-  Mortality  at 
tality  varies  very  much.      Of  both  sexes,  22  per  cent,  die  different  peri- 
before  they  are  one  year  old,  and  37  per  cent,  before  they 
are  five  years  old.     Male  infants  are,  however,  more  liable  to  die  imme- 
diately after  birth  than  female,  but  at  the  close  of  about  two  years  their 
mortality  is  the  same.     Nine  twentieths  of  the  whole  number  born  die 
before  they  are  fifteen  years  of  age,  that  is,  before  they  have  become  use- 
ful to  the  community. 

The  mortality  among  girls  increases  between  14  and  18,  and  among 
men  between  21  and  26.     In  France  and  Belgium,  from  26  Relative  raor. 
to  30  is  the  epoch  of  marriage,  and  at  this  period  the  mortal-  tality  of  the 
ity  is  the  same  in  both  sexes.     It  then  increases  for  the  s 
women  during  the  years  of  childbearing,  and  afterward  again  becomes 
equal  for  both.     At  25  years  half  the  births  are  dead.     The  mean  life 
may  be  estimated  at  33  years.     The  maximum  expectancy  of  life  is  at 
5  years,  at  which  age  the  risk  of  mortality  is  suddenly  reduced,  and  be- 
comes small  till  puberty,  when,  especially  among  girls,  it  becomes  great. 
From  60  to  65  the  chances  of  life  are  again  at  a  minimum. 

To  the  foregoing  statements,  in  which  contrasts  have  been  drawn  be- 
tween the  male  and  female,  the  following  may  be  added :  Not  only  is 
there  a  difference  in  the  entire  stature,  but  the  different  portions  of  the 

M  M 


546  PECULIAEITIES    OF   THE    FEMALE. 

Comparison  of  body  have  not  the  same  relative  size.  The  capacity  of  the 
*f Vemale and  s^u^  *n  *ne  fema^e  is  ^ess  »  tne  body  is  longer ;  the  lower  ex- 
female,  tremities  shorter ;  the  pelvis  of  greater  size,  especially  in  its 
transverse  diameter;  the  heads  of  the  thigh  bones,  therefore,  farther  apart, 
and  the  bones  themselves  including  a  larger  angle  than  in  the  case  of  the 
male ;  the  chest  and  the  abdomen  are  respectively  more  convex ;  the  trans- 
verse diameter  at  the  shoulders  smaller,  and  the  upper  extremities,  like 
the  lower,  shorter ;  the  hands  and  feet,  fingers  and  toes,  of  less  size.  The 
surface  presents  a  more  elegantly  rounded  form,  without  angularities ; 
the  skin  thinner  and  more  translucent ;  the  hair  of  the  head  is  longer 
and  finer,  but  other  portions  of  the  skin  less  covered  with  hair ;  the  nails 
smaller  and  thinner. 

The  strength  of  the  female  is  to  that  of  the  male  as  16  to  26.  Her 
Functional  e  musc^es  contract  with  less  energy,  and  are  more  easily  wea- 
cuiiarities  of  ried.  The  peculiarities  of  the  construction  of  the  bones  of 

female.  j^  pe}vis  an(j  cnest  respectively  give  rise  to  peculiarities  in 
the  movements  of  the  lower  and  upper  extremities ;  hence  the  character- 
istic manner  of  walking  and  movement  of  the  arm  in  attempting  to  throw 
a  stone.  In  the  chapter  on  the  voice  we  have  already  pointed  out  the 
female  peculiarities  in  speaking  and  singing,  and  its  more  acute  quality. 

With  respect  to  her  moral  and  intellectual  peculiarities,  these  are  man- 
Her  moral  and  ^este^  ^rom  *ne  earliest  infancy  in  the  sports  and  games 
intellectual  pe-  which  she  instinctively  follows.  Coming  to  maturity  more 
rapidly  than  the  male,  she  abandons  these,  though  they  may 
still  be  enjoyed  by  boys  of  her  own  age,  whom,  for  the  course  of  a  year 
or  two,  she  regards  with  neglect  or  even  disrespect,  a  feeling  soon  after 
to  be  followed  by  timidity.  Education  and  the  position  in  which  she 
may  have  been  placed  may,  to  a  certain  extent,  control  or  disguise  her 
habits,  but  they  can  never  wholly  obliterate  the  striking  predominance 
of  her  moral  over  her  intellectual  qualities,  as  compared  with  man.  Es- 
sentially religious,  her  faith  is  applied  to  almost  all  the  ordinary  affairs 
of  life,  though  when  she  finds  that  she  has  been  deceived  she  is  ever  dis- 
trustful. From  the  earliest  times  it  has  been  remarked  that  her  revenge, 
more  particularly  when  it  concerns  wounded  pride,  is  implacable.  Much 
more  than  the  male  she  is  delighted  with  the  adornments  of  dress.  Her 
reasoning  powers  are  less  vigorous,  though  her  sensations  are  more  acute, 
yet  she  bears  pain  with  more  resignation  than  man.  Her  judgment  is 
not  so  evenly  balanced,  and  is  often  perverted  by  the  preponderance  of 
her  feelings.  It  has  been  asserted  that  these  moral  and  intellectual  pe- 
culiarities which  she  presents  when  compared  with  man  are  distinctly 
traceable  to  the  phrenological  predominance  of  the  moral  over  the  intel- 
lectual regions  of  the  brain. 

The  physiologist  who  is  thus  obliged  to  speak  of  the  constitutional 


EPOCHS   OF   LIFE.  547 

and  mental  imperfections  of  the  female,  may  be  permitted  to  turn  with 
delight  from  the  dry  details  of  statistics  and  anatomy  to  the  family  and 
social  relations,  for  it  is  therein  that  her  beautiful  qualities  shine  forth. 
At  the  close  of  a  long  life,  checkered  with  pleasures  and  misfortunes, 
how  often  does  the  aged  man  with  emotion  confess  that,  though  all  the 
ephemeral  acquaintances  and  attachments  of  his  career  have  ended  in  dis- 
appointment and  alienation,  the  wife  of  his  youth  is  still  his  friend.  In 
a  world  from  which  every  thing  else  seems  to  be  passing  away,  her  affec- 
tion alone  is  unchanged ;  true  to  him  in  sickness  as  in  health,  in  misfor- 
tune as  in  prosperity,  true  in  the  hour  of  death.  When  the  schemes  that 
occupied  his  active  years  have  vanished,  or,  if  realized,  are  now  no  more 
to  him  than  vanities  which  hardly  fasten  his  thoughts ;  when,  in  the 
feeble  extremity  of  age,  every  thing  is  a  burden  to  him,  and  the  pass- 
ing excitements  of  others  can  not  even  arouse  his  attention,  the  echo  of 
those  prayers  is  still  heard  which  his  unskillful  tongue  first  learned  at  his 
mother's  knee.  The  stern,  the  avaricious,  the  hard-hearted,  the  intellect- 
ual, all  are  equally  brought  to  confess  who  was  their  first  and  who  is  their 
last  true  friend. 

The  necessities  of  society  have  led  to  the  establishment  of  artificial 
epochs  in  the  life  of  man.  In  most  countries,  the  first  recog-  Artificial 
nized  movements  of  the  foetus  are  taken  as  the  period  from  eP°chs  of  life- 
which  independent  life  begins,  and  the  twenty-first  year  is  fixed  as  the 
time  of  maturity.  These  arbitrary  dates  answer  the  purpose  very  well, 
but  they  have  not  that  physiological  significance  which  is  commonly  sup- 
posed, for  neither  of  them  coincides  with  any  great  change  in  the  mode 
of  life.  Of  the  metamorphoses  through  which  we  pass,  the  final  one,  oc- 
curring at  puberty,  which  separates  the  merely  vegetative  from  the  re- 
productive period  of  life,  is,  under  the  circumstances  of  the  case,  with  the 
exception  of  the  assumption  of  aerial  respiration  at  birth,  the  only  obvious 
one.  The  change  which  then  ensues  is  in  no  respect  less  marked  than 
the  passage  to  the  perfect  or  imago  state  by  insects.  Development  sud- 
denly takes  on  a  new  phase,  and  with  the  physical  change  correspond- 
ingly occur  changes  in  the  psychical  endowments — modesty  and  woman- 
ly sentiments  in  the  one  sex,  courage,  the  perception  of  honor,  and  manly 
qualities  in  the  other,  the  capability  of  mutual  love  in  both.  Even  among 
animals  under  the  same  conditions,  analogous  results  are  presented,  though 
in  a  less  refined  way. 

The  human  species  is  no  exception  to  the  observation  long  ago  made, 
that  the  undue  extension  of  the  vegetative  period  of  life  into  Encroachment 
the  reproductive  is  at  the  expense  of  the  latter.  In  the  same 
manner  that  a  tree  overladen  with  foliage  presents  its  flow-  life. 
ers  scantily,  so  a  love  for  the  pleasures  of  the  table  and  a  predominating 
epicurean  turn  is  often  the  indication  of  incapability. 


548  CHANGE  OF  MENTAL  QUALITIES. 

Up  to  the  fourteenth  year,  the  human  being  lives  solely  for  itself;  its 
Gradual  instincts  are  for  the  gratification  of  its  present  wants,  and 
change  in  the  tjlose  wants  are,  for  the  most  part,  connected  with  its  vegeta- 
ties.  tive  development.  After  that  period  its  life  is  for  the  future, 

and  is  in  relation  to  the  race.  With  this  more  elevated  condition,  new 
emotions  and  passions  have  been  awakened ;  there  is  a  gradual  unfolding 
of  the  mental  powers,  and  a  balancing  arising  from  increased  knowledge 
and  increased  experience ;  yet,  even  now,  the  mental  qualities  that  are 
most  marked  are  only  the  extension  of  those  the  germ  of  which  may  be 
discovered  at  the  first  dawn  of  reason,  and  the  same  may  be  said  even 
of  our  intellectual  impressions.  The  ideas  we  have  gathered  as  members 
of  a  family  are  reproduced  and  expanded  in  our  religious  views,  and  the 
government  of  GOD  is  presented  to  the  human  heart  less  acceptably  when 
he  is  set  forth  as  the  Almighty  Maker  of  the  world  than  as  the  Universal 
Father  and  Giver  of  all  good. 

In  a  preceding  chapter  I  have  already  shown  how  the  existence  of  the 
Parallel  of  cor-  immaterial  spirit  of  man  may  be  investigated  physiologically, 
mental Tevel-  ^  ma7  no*  ^e  out  of  place  here  to  dispose  of  an  argument 
opment.  that  some  have  insisted  on,  that,  since  the  development  of 

the  mind  proceeds  in  an  equal  step  with  the  development  of  the  body, 
each  expanding  or  declining  with  the  other,  the  dissolution  of  the  animal 
fabric  is  the  token  of  the  death  of  the  soul.  Against  this  doctrine  the 
whole  human  family,  in  all  ages,  has  borne  its  testimony,  and,  if  univer- 
sal ^impressions  arise  from  physical  constitution  far  more  than  they  do 
from  tradition,  it  may  be  truly  said  that  that  doctrine  is  incompatible 
with  the  organization  of  man.  Probably  there  is  no  question  which  has 
received  a  greater  amount  of  individual  and  general  attention — none 
which  has  more  deeply  exercised  the  thought  of  the  profoundest  intellect ; 
and  what  is  the  actual  result  ?  Whatever  may  be  the  social  state,  bar- 
barous or  polished,  whatever  the  manner  of  life,  whatever  the  climate, 
whatever  the  form  of  religion,  the  assertion  of  the  existence  of  the  spirit 
after  death  is  so  universal,  that  it  may  be  termed  one  of  the  organic  dog- 
mas of  our  race.  Indeed,  we  may  affirm  that  the  mind  has  to  be  edu- 
cated, trained,  or  strained  before  it  becomes  capable  of  an  opposite  view, 
which,  even  then,  will  be  doubtingly  entertained. 

If  there  is  a  point  in  natural  philosophy  which  may  be  regarded  as 
independent  ^na^7  settled,  it  is  the  imperishability  of  the  chemical  ele- 
existence  of  ments  and  the  everlasting  duration  of  force.  With  the  sys- 
tem of  nature  existing  as  it  is,  we  can  not  admit  that  an  atom 
of  any  kind  can  ever  be  destroyed ;  and  a  like  assertion  may  be  made 
of  force.  Heat  may  give  rise  to  motion,  motion  to  electricity,  electricity 
to  heat :  one  kind  of  force  may  be  converted  into  another,  there  being  a 
perfect  correlation  or  quality  of  substitution  among  them.  The  quan- 


THE   SOUL.  549 

tity  of  power  is  now  the  same  as  it  ever  was.  Its  variations  are  analo- 
gous to  the  apparent  transmutations  of  ponderable  material.  They  are 
mere  metamorphoses. 

Matter  and  force  are  equally  incapable  of  destruction.  Each  constitu- 
ent atom  of  the  animal  mechanism,  though  it  may  be  dismissed  for  the 
time  as  useless,  is  not  lost,  but  sooner  or  later  is  economized  in  some 
organic  form  again.  The  heat  which  seems  to  arise  from  the  most  in- 
significant muscular  contraction  has  been,  so  to  speak,  many  a  time  in 
existence  before,  and  after  it  has  escaped  from  the  system  is  not  lost  to 
the  world,  but  discharges  one  function  after  another  forever ;  and  if  thus 
neither  matter  nor  force  can  die,  it  would  be  a  great  anomaly  if  the  prin- 
ciple of  conscious  identity  were  capable  of  annihilation.  Like  them,  it 
may  be  capable  of  modification  or  change,  and,  like  them,  it  is  not  capa- 
ble of  loss  of  existence.  The  creeds  of  various  nations  recognize  this 
great  truth ;  they  differ  only  in  their  ideas  of  what  that  future  state  of 
modification  may  be. 

Perhaps  in  some  age  hereafter  physiology  will  find  herself  sufficiently 
advanced  to  offer  her  opinion  on  this  profound  topic,  for  I  can  not  think 
that  GOD  has  left  us  without  a  witness  in  this  matter,  even  in  the  struc- 
ture and  development  of  the  body  itself.  From  the  moment  that  we  see 
the  first  traces  of  the  nervous  mechanism  lying  in  the  primitive  groove, 
we  recognize  the  subordination  of  every  other  part  to  that  mechanism. 
For  it,  and  because  of  it,  are  introduced  the  digestive,  the  circulatory, 
the  secretory,  the  respiratory  apparatus.  They  are  merely  its  ministers. 
And,  fastening  our  attention  on  the  course  which  it  pursues,  we  see  that 
it  is  at  once  a  course  of  concentration  and  development.  The  special  is 
at  each  instant  coming  out  of  the  more  general,  and,  from  the  beginning 
to  the  end,  the  whole  aim  is  at  psychical  development.  The  germinal 
membrane  is  cast  away  as  soon  as  a  stomach  can  be  prepared,  aquatic 
respiration  ceases  as  soon  as  aerial  can  be  maintained.  The  scaffolding 
that  was  of  use  at  one  moment  is  thrown  aside  as  soon  as  a  new  eleva- 
tion is  reached.  The  germ,  the  embryo,  the  infant,  are  only  successive 
points  in  a  progress  which  at  every  instant  displays  this  casting  away 
of  the  means  that  have  been  used  as  soon  as  they  are  done  with.  That 
is  the  style  in  which  the  work  is  carried  on.  The  principle  which  ob- 
scurely animated  the  germ  is  the  same  which  in  a  higher  way  animates 
the  embryo,  and  this  again  is  the  same  which,  in  a  more  exalted  condi- 
tion, animates  the  infant  and  the  man.  The  cloudy  speck  which  ushers 
in  the  phantasmagoria  of  life  expands  as  the  great  Artist  directs  until 
every  lineament  has  become  visible. 

That  active  agent  which  was  first  laid  in  a  fold  of  the  germinal  mem- 
brane was  not  annihilated  when  its  type  of  life  was  changed  to  placental 
and  therefore  aquatic  respiration.  It  withstood  the  shock  when  again, 


550  THE   SOUL. 

after  a  due  season,  it  was  suddenly  made  to  breathe  the  air.  Arrived  at 
the  mature  condition,  there  is  not  in  its  companion-body  a  single  particle 
that  was  present  at  birth.  All  has  changed.  And,  what  is  still  more 
important,  not  only  has  there  been  this  interstitial  removal,  but,  in  suc- 
cession, the  very  nature  of  every  one  of  its  organs  has  changed.  It  is 
needless  now  to  repeat  how  many  different  systems  of  nutrition  it  has 
depended  on — how  many  sorts  of  stomachs  in  succession  it  has  had — 
how  it  has  breathed  by  a  membrane,  by  gills,  and  by  lungs — how  it  has 
carried  on  its  circulation  without  a  heart,  with  a  heart  of  one  cavity,  and 
finally  with  one  of  four.  Through  all  these  losses  and  changes  the  im- 
material principle  has  passed  unscathed,  and  even  gathering  strength. 
In  the  broadest  manner  that  a  fact  can  be  set  forth,  we  see  herein  the 
complete  subordination  of  structure  and  the  enduring  character  of  spirit. 
Whatever  may  be  the  mechanism  that  is  wanted,  it  is  in  readiness  for  its 
time ;  and  when  it  has  finished  its  duty,  is  neglected  and  disappears. 
There  is,  therefore,  a  sound  reason  in  the  conclusion  to  which  mankind, 
perhaps  from  a  mere  instinctive  impression,  have  come,  that  the  soul  will 
exist  after  death,  for,  after  surviving  so  many  mutations,  the  removal  of 
so  many  of  what  seemed  to  be  its  firm  and  essential  supports,  we  are  jus- 
tified in  expecting  that  it  will  bear  without  ruin  the  entire  withdrawal  of 
the  whole  scaffolding. 

As  I  have  pointed  out,  we  have  precisely  the  same  reason  for  believ- 
ing the  existence  of  the  immortal  spirit  that  we  have  for  knowing  that 
there  is  an  external  world.  The  two  facts  are  of  the  same  order.  Of 
the  future  continuance  of  that  external  world,  irrespective  of  ourselves, 
we  entertain  no  doubt ;  indeed,  in  certain  cases,  as  in  those  presented  by 
astronomy,  we  are  able  to  tell  its  state  a  thousand  years  hence.  So  long 
as  our  attention  was  confined  to  statical  physiology,  every  thing  connect- 
ed with  the  subject  now  under  consideration  was  enveloped  in  darkness, 
but  it  will  be  very  different  when  dynamical  physiology  begins  to  be 
cultivated  —  dynamical  physiology,  which  speaks  of  the  course  of  life, 
of  organs,  individuals,  and  races.  The  law  of  development  will  guide 
us  to  an  interpretation  of  many  things  which  are  now  shrouded  in  ob- 
scurity, and  teach  us,  from  a  consideration  of  what  we  have  learned  of 
our  past,  and  what  we  know  of  our  present,  what  we  may  expect  of  our 
future  state ;  and  then  it  will  appear  that  the  universal  opinion  of  the 
ages  and  nations  is  not  a  vulgar  illusion,  but  a  solemn  philosophical  fact. 

So,  therefore,  the  decline  of  the  mental  faculties  with  advancing  years 
is  no  indication  of  the  hebetude  of  the  spirit,  or  premonitory  to  its  final 
dissolution.  It  is  only  the  gradual  wearing  out  of  the  instrument,  the 
intervention  of  which  has  established  relations  with  the  outer  world. 
When  a  tool  becomes  blunted  and  old,  the  workman  can  no  longer  man- 
ifest his  former  skill ;  but  the  skill  may  nevertheless  remain.  Though 


OF   SLEEP.  551 

the  apparatus  for  the  reception  of  external  impressions,  as  well  as  that 
for  voluntary  action,  may  be  failing,  it  implies  nothing  as  regards  the 
prime  mover.  The  eye  may  be  dim,  the  ear  dull,  and  touch  imperfect, 
the  voice  may  be  feeble,  and  the  limbs  trembling,  but  all  this  indicates 
nothing  more  than  that  what  has  been  passed  through  so  often  before 
is  about  to  be  passed  through  again.  The  organs  that  have  done  their 
duty  are  to  be  cast  away,  but  the  result  of  their  action  is  to  remain. 

It  may  not,  perhaps,  fall  within  the  proper  compass  of  a  treatise  on 
physiology  to  speak  of  that  future  condition,  and  yet  so  deeply  The  future 
interesting  are  these  subjects  to  all  men  that  a  single  observa-  state- 
tion  may  in  this  place  be  excused.  The  whole  course  of  life,  from  its 
very  beginning,  has  been  one  of  development  and  concentration.  We 
comprehend  this  the  more  perfectly  as  we  extend  our  views  beyond  our 
present  state,  and  examine  what  we  have  in  succession  been,  and  in  what 
manner  our  existing  condition  was  reached.  It  is  not  credible  that  that 
system  is  to  be  all  at  once  abandoned,  or  replaced  by  a  contradictory  one. 
Such  is  not  the  style  in  which  the  affairs  of  the  organic  world  are  at  any 
time  carried  on.  The  slowly  emerging  consequences  of  the  primitive 
law  ccme  forth  one  after  the  other  in  their  proper  and  unvarying  sequence, 
and  the  law  holds  on  inexorably  forever.  And  since  we  may  say  that, 
throughout  those  prior  states,  the  idea  aimed  at  is  the  isolation  of  a  con- 
scious intelligence,  every  organ  being  shaped  and  every  function  bent  to 
that  end,  we  are  reasonably  led  to  the  expectation  that  in  a  future  state 
that  archetype  will  be  completely  reached.  It  would  be  strange  indeed 
if  a  blank  oblivion  should  crown  such  a  work. 


CHAPTER  VI. 

OF  SLEEP  AND  DEATH. 

Causes  of  the  Necessity  for  Sleep. — Its  Duration  and  Manner  of  Approach. — Manner  of  Awak- 
ing.—  Cause  of  Night-sleep. — Increased  Warmth  required. —  Connection  of  Sleep  and  Pood. 

Of  Dreams :  their  Origin  and  Phenomena. — Somnambulism. — Nightmare. 

Of  Death. —  Old  Age. — Internal  Causes  of  Decline. — Death  by  Accident  and  by  Old  Age. —  The 
Hippocratic  Face. — Final  Insensibility. 

Isx.  OF  SLEEP. 

ONE  third  of  the  life  of  man  is  spent  in  sleep,  a  condition  of  modified 
sensibility,  in  which  the  mind  performs  its  functions  in  an  im- 
perfect way,  and  voluntary  motion  is  nearly  suspended.     This 
state,  occupying  so  large  a  portion  of  the  short  period  of  time  allotted  to 
us,  is  therefore  well  deserving  of  the  consideration  of  the  physiologist, 


552  APPROACH   OF  SLEEP. 

and  the  more  so  since  it  presents,  in  the  various  phenomena  of  dreams, 
significant  illustrations  of  the  manner  of  action  of  the  nervous  system. 

All  animals  sleep.  Many,  perhaps  most,-  dream.  The  necessity  for  a 
season  of  repose  arises  from  the  preponderance  of  the  waste  of  the  sys- 
tem ove/  its  repair  during  our  waking  hours.  By  bringing  the  animal 
functions  into  a  condition  of  rest,  an  opportunity  is  afforded  for  renova- 
tion, and  the  equilibrium  can  be  maintained. 

In  early  infancy,  when  it  is  necessary  for  the  nutritive  operations  to  be 
. .,  carried  forward  with  the  utmost  vigor,  and  attended  with  as 

Causes  of  the  &. 

necessity  for  little  waste  as  possible,  the  whole  time  is  spent  in  sleeping 
and  eating.  The  waking  period  is  gradually  increased  as  the 
child  advances,  but  not  so  as  to  make  it  continuous,  for  the  day  is  broken 
into  intervals  of  sleep.  Even  at  three  or  four  years  of  age  we  sleep  more 
Duration  and  tnan  once  a  ^aj-  ^n  mature  life  eight  hours  are  on  an  aver- 
depth  of  sleep.  age  required,  but  the  precise  time  varies  with  different  indi- 
viduals, and  even  with  the  same  individual  in  different  constitutional 
states.  The  time  is  not,  however,  always  a  true  measure  of  the  amount 
of  rest,  for  sleep  varies  very  much  in  the  degree  of  its  completeness  or 
intensity ;  there  is  a  slumber  so  disturbed  that  we  are  unrefreshed  by  it, 
and  a  sleep  so  profound  that  we  awake  weary.  Old  age,  as  it  advances, 
admonishes  us  to  spare  the  system  as  much  as  we  may,  for  repair  is  con- 
ducted with  difficulty  ;  and  this  period,  characterized  by  its  resemblance 
in  so  many  respects  to  childhood,  like  it,  is  often  marked  by  frequently- 
recurring  and  prolonged  slumber.  Moreover,  various  accidental  and 
other  circumstances  are  liable  at  all  times  to  disturb  its  proper  periodic- 
ity— a  warm  afternoon,  a  hearty  dinner,  an  ill-ventilated  apartment,  mo- 
notonous sounds,  the  attention  devoted  to  one  object,  bodily  quiescence, 
ceasing  to  think,  the  use  of  narcotics,  extreme  cold,  a  horizontal  posi- 
tion, &c. 

Sleep  is  commonly  preceded  by  a  sense  of  drowsiness  of  more  or  less 
Approach  of  intensity,  which  is  gradually  followed  by  a  loss  of  sensibility, 
sleep.  Objects  cease  to  make  an  impression  on  the  eyes,  the  lids  be- 

come heavy  and  close.  If  we  are  not  in  the  horizontal  position,  but  re- 
quire muscular  support,  as  in  sitting,  the  head  droops,  and  the  hands  seek 
a  support.  Successively  the  senses  of  smelling,  hearing,  and  touch  pass 
away,  as  the  sight  has  done ;  but,  before  this  progress  is  completed,  we 
start  at  any  sound  or  disturbance,  voluntary  muscular  action  being  in- 
stantly assumed,  though  in  the  midst  of  a  surprise.  "We  are  nodding.  If 
we  are  in  the  horizontal  position,  as  in  bed,  the  body  is  thrown  into  a 
form  requiring  the  least  muscular  exertion — the  limbs  are  semiflexed. 
As  sight,  smell,  hearing,  touch,  again  in  succession  fail,  all  voluntary  mo- 
tions cease,  those  which  are  now  executed  being  of  a  purely  automatic 
kind.  The  eyes  are  turned  upward  and  inward,  the  iris  is  contracted, 


MANNER   OF  AWAKENING.  553 

the  heart  and  the  lungs  act  more  slowly  but  more  powerfully ;  a  gentle 
delirium,  which  exists  while  the  centres  of  the  special  senses  are  coming 
into  repose,  introduces  us  to  profound  and  unconscious  sleep. 

This  condition  of  profound  sleep,  though  it  may  be  quickly,  is  yet 
gradually  reached  by  passing  through  certain  well-marked  progress  of 
stages.  Once  gained,  we  sleep  with  heaviness  in  the  early  night-sleep. 
part  of  the  night,  and  more  and  more  lightly  as  morning  approaches. 
It  would,  however,  be  erroneous  to  suppose  that  this  falling  into  insensi- 
bility and  awakening  are  perfectly  continuous  events  ;  there  are,  undoubt- 
edly, subordinate  periods  of  more  and  less  complete  repose,  but  under 
no  circumstances  are  we  ever  aware  that  we  are  asleep. 

At  any  time  of  the  night  sleep  may  be  abruptly  broken,  the  mind  re- 
suming its  power  after  passing  through  a  momentary  interval  Manner  of 
of  confusion.  Toward  the  close  of  the  customary  time,  the  awakening, 
senses  resume  their  power  in  an  order  inverse  to  that  in  which  they  lost 
it — the  touch,  the  hearing,  the  smell,  the  sight.  For  a  short  period  after 
awakening,  the  organs  seem  to  be  in  a  state  of  unusual  acuteness,  more 
particularly  that  of  sight — an  effect  arising  from  the  obliteration  of  the 
vestiges  of  old  impressions.  From  profound  sleep  we  pass  to  the  wak- 
ing state  through  an  intermediate  condition  of  slumber.  In  the  former, 
the  movements  which  we  may  execute,  under  the  influence  of  external 
impressions,  are  wholly  of  an  automatic  kind,  such  as  turning  in  bed  in 
various  positions.  The  -length  of  time  spent  in  sleep  and  slumber  re- 
spectively is  by  no  means  constant,  many  causes  increasing  the  one  at 
the  expense  of  the  other.  On  awakening,  we  are  apt  to  indulge  in  cer- 
tain muscular  movements — we  rub  our  eyes,  stretch,  and  yawn.  If  we 
are  suddenly  aroused,  our  motions  are  feeble  and  uncertain  on  attempt- 
ing to  walk  at  once ;  but  if  we  spontaneously  awake  at  an  unusual  period, 
and  more  particularly  if  it  be  toward  the  morning,  we  commonly  remark 
a  clearness  of  intellect  or  mental  power.  Many  of  our  most  judicious 
and  correct  conclusions  occur  to  us  under  these  circumstances. 

Though  it  is  said  that  the  sleep  of  man  lasts  about  eight  hours,  there 
are  many  variations.  Authentic  cases  are  on  record  in  which  Maximuin  and 
individuals  have,  for  a  considerable  time  and  apparently  with-  minimum 
out  injury,  slept  only  for  one  hour,  and  others  in  which  that  engt 
state  has  been  prolonged  for  an  entire  week.  Man  shows  much  greater 
differences  than  other  animals ;  birds,  for  instance,  sleep  lightly,  and  cold- 
blooded animals  generally  profoundly.  Since  the  object  of  sleep  is  to 
afford  an  opportunity  for  repairing  the  waste  of  the  system,  the  length 
of  the  needful  time  depends  on  conditions  that  are  themselves  variable : 
the  extent  of  the  antecedent  waste,  and  the  rapidity  of  the  repair.  In 
winter  we  sleep  longer  and  usually  deeper  than  in  summer,  for  the  hour- 
ly waste  in  winter  is  greater.  Habit,  however,  controls  us  very  much. 


554  NIGHT-SLEEP. 

It  has  been  supposed  by  some  that  it  is  to  habit  that  our  tendency  to 
Cause  of  night-  sleep  at  night  is  to  be  imputed.  It  is,  however,  more  properly 
sleep.  to  be  attributed  to  the  ordinary  circumstances  of  our  life — the 

day  being  spent  in  muscular  or  mental  exercise,  since  we  can  then  see 
to  perform  our  duties,  and  this  tax  upon  the  system  being  necessarily 
followed  by  a  feeling  of  weariness.  Those  animals  which  seek  their  food 
in  the  dark  sleep  by  day.  It  is  not,  therefore,  to  any  external  physical 
condition  that  we  should  impute  our  nocturnal  sleep,  but  to  the  interior 
condition  of  our  system,  though  it  is  quite  true  that  physical  agents, 
such  as  cold,  and  others  that  have  been  mentioned,  will  provoke  a  sensa- 
tion of  drowsiness. 

In  sleep  we  require  additional  warmth,  and  this  we  obtain  by  instinct- 
Increased  ively  using  more  clothing  for  the  purpose  of  economizing  the 
warmth  re-  animal  heat.  The  amount  of  caloric  generated  in  the  system 
eep*  is  diminished  through  the  cessation  of  muscular  exercise, 
and  therefore  reduction  of  decay.  The  same  may  be  said,  to  a  certain 
extent,  of  the  waste  of  the  brain  through  its  intellectual  acts,  and  of  the 
nervous  system  generally.  This  diminished  amount  of  interstitial  death 
corresponds  with  a  diminished  respiration,  the  hourly  amount  of  oxygen 
consumed  exhibiting  a  decline.  The  negro,  who  is  much  more  sensitive 
than  the  white  man  to  this  decline  of  temperature,  instinctively  envelops 
his  head  with  clothing,  so  that  the  air  may  be  warmed  by  its  conta'et 
therewith  before  it  enters  the  respiratory  organs.  For  the  same  reason, 
he  sleeps  with  his  head  toward  the  fire,  while  the  white  man  sleeps  with 
his  away.  On  similar  principles  we  may  account  for  the  control  which 
food  has  over  sleep,  the  one  seeming,  to  a  certain  degree,  to  replace  the 
other.  The  French  proverb  says,  "He  who  sleeps,  dines,"  and  this  is 
Uniformity  of  true ;  for  during  sleep  the  waste  of  the  system  is  reduced  to 
ed  wiSTmii-*"  a  mmimum,  and  the  necessity  for  food  correspondingly  di- 
formityoffood.  minished.  The  quality  of  the  food  likewise  exerts  an  influ- 
ence on  the  length  of  sleep,  for  that  which  is  of  a  nutritious  kind,  and 
easily  assimilated,  can  more  speedily  execute  whatever  repairs  the  sys- 
tem may  demand.  It  is  probably  owing  to  his  variable  diet  that,  even 
in  a  state  of  perfect  health,  man  is  so  variable  a  sleeper,  and  that  ani- 
mals, the  nature  of  whose  food  is  so  constant,  sleep  with  so  much  uni- 
formity. 

By  some  it  has  been  supposed  that  the  amount  of  sleep  required  by 
different  animals  is  dependent  upon  the  size  of  their  brain;  but  if  we 
keep  in  view  that  the  object  of  sleep  is  the  repair  of  waste,  and  that  this 
is  accomplished  by  the  agency  of  the  different  mechanisms  involved  in 
organic  life,  we  can  easily  see  that  such  a  statement  can  not  be  true.  Its 
fallacy  appears  from  common  observation,  apart  from  any  physiological 
considerations.  The  brain  of  a  turtle  or  of  a  serpent  is  relatively  small, 


OF   DEEAMS.  555 

and  yet  those  animals  sleep  long  and  profoundly ;  but  if  we  reflect  on 
how  many  different  conditions,  external  and  internal,  the  repair  of  waste 
depends,  we  shall  see  that  the  time  of  sleep  can  not  have  any  such  arbi- 
trary measure  as  that  of  the  size  of  the  brain.  Among  external  causes 
which  influence  the  rate  of  repair  may  be  mentioned  the  digestibility  of 
the  food,  some  varieties  of  which,  by  reason  of  their  chemical  or  physi- 
cal qualities,  yield  more  slowly  than  others.  The  internal  causes  are  very 
numerous :  the  size  of  the  digestive  organs  in  relation  to  the  Conditiong  of 
body,  and  the  energy  with  which  their  function  is  accom-  the  duration  of 
plished ;  the  condition  of  development  of  the  absorbent  sys-  s  eep* 
tern,  and  the  rapidity  of  its  action ;  the  rate  of  the  circulation  of  the 
blood,  which  hurries  the  nutritive  supply  in  its  course ;  the  amount  of 
oxygen  introduced  into  the  system  by  the  respiratory  apparatus,  which 
discharges,  as  we  have  elsewhere  explained,  the  double  function  of  re- 
moving the  wasted  products  of  decay,  and  of  grouping  into  appropriate 
forms,  so  as  to  be  available  for  their  uses,  the  elements  of  nutrition  that 
are  being  introduced.  All  these,  and  other  conditions  that  might  be 
named,  determine  the  rate  at  which  repair  can  be  executed,  and  therefore 
the  necessary  duration  of  sleep.  If,  out  of  these  various  elements,  we 
were  to  select  one  which  would  represent  it,  the  activity  of  the  respira- 
tory organs  would  afford  a  more  accurate  measure  than  the  size  of  the 
brain. 

As  the  necessary  repairs  are  accomplished,  we  pass  through  a  condi- 
tion of  slumber,  and  our  organs  gradually  awake  in  the  manner  that  has 
been  described.  It  is  during  this  intermediate  passage,  that  is,  toward 
the  morning  chiefly,  as  the  brain  is  resuming  its  functions,  of  dreams : 
that  dreams  occur.  They  may,  however,  happen  at  any  other  their  ™s™> 
period  of  the  night,  though  then  they  are  liable  to  present  greater  in- 
congruities and  more  obvious  violations  of  the  proper  order  of  events. 
It  is  quite  correct  that  morning  dreams  are  more  likely  to  be  prophetic, 
for  they  are  more  likely  to  be  in  themselves  true. 

Dreams  never  strike  us  with  surprise,  no  matter  what  may  be  the  ex- 
traordinary scenery  they  present — no  matter  how  great  the  violations  of 
truth  and  reality.  The  dead  may  appear  with  the  most  astonishing  clear- 
ness ;  their  voices,  perhaps  long  forgotten,  may  be  heard ;  we  may  be 
transported  to  places  where  we  have  spent  past  years  of  our  lives ;  com- 
binations of  the  most  grotesque  and  impossible  kinds  may  be  spread  be- 
fore us :  we  accept  all  as  reality,  perhaps  not  even  suspecting  that  we 
dream.  The  germs  from  which  have  originated  all  these  strange  com- 
binations are  impressions  stored  up  in  the  registering  ganglia  of  the  brain, 
more  particularly  in  its  optic  thalami.  These,  as  outward  impressions 
have  for  the  time  ceased,  are  enabled  to  attract  the  attention  of  the  mind, 
and  emerge  from  their  latent  state.  That  all  dreams  originate  in  such 


556  OF   DREAMS. 

impressions  is  illustrated  by  the  history  of  the  blind,  who  still  dream 
of  things  that  they  formerly  saw.  Thus  it  is  stated  that  Huber,  after 
he  had  been  blind  for  fifty  years,  still  dreamed  of  things  he  had  seen 
when  a  boy.  But  little  explanation  can  be  given  of  the  manner  in  which 
these  vestiges  may  be  grouped — a  grouping  which  is  so  frequently  in  vi- 
olation of  all  correctness  that  a  dream  which  presents  us  with  a  logical 
sequence  of  events,*  and  which  we  recognize  on  awakening  to  be  natu- 
rally true,  is  sure  to  be  an  impressive  one ;  and  yet  we  can  not  doubt 
that  the  causes  which  suggest  dreams  are  often  purely  physical,  as  when, 
in  dropsy  of  the  chest,  the  dreamer  fancies  he  is  drowning,  or  even  suf- 
fers under  the  same  delusion  when  his  hand  is  dipped  in  water ;  or  when 
a  candle  is  earned  into  the  room,  and  he  awakens  stricken  with  terror 
that  the  house  is  on  fire ;  or,  on  the  occurrence  of  noise,  he  believes  that 
he  is  in  a  thunder-storm,  or,  perhaps,  on  a  field  of  battle.  Hence  arises 
an  automatism  which  becomes  most  striking  when  the  dreamer  answers 
questions  put  in  a  whisper  to  him,  an  incident  of  which  cases  are  record- 
ed in  which  individuals  have  revealed  important  events  of  their  lives, 
which,  when  waking,  they  would  never  have  divulged. 

Automatic  actions  are  usually  considered  as  occurring  without  sensa- 
tion, but  this,  in  some  instances,  as  in  those  now  before  us,  can  not  be 
regarded  as  altogether  true. 

Suggested  thus  by  external  circumstances,  or  arising  spontaneously 
Deceptive  ap-  without  any  obvious  cause,  dreams  pass  before  us  with  an 
pearance  of  air  of  truthfulness  so  imposing  that  we  never  suspect  their 

truth  in  dreams.    „  ,,  T^  ,       A      ,  - 1  .,1         ,1         i  i 

fallacies.  It  may  be  truly  said  that  they  have  a  logic  ot 
their  own.  Indeed,  so  complete  is  the  illusion,  that  instances  are  not 
wanting,  and  many  have  been  recorded,  in  which,  at  the  moment  of 
awakening,  the  sleeper  has  been  struck  with  the  correctness  of  the  con- 
clusions at  which  he  had  arrived,  and  it  was  not  until  he  had  recovered 
from  the  delirious  confusion  of  the  moment,  and  reason  had  resumed  her 
sway,  that  he  perceived  how  incorrect  they  were.  Thus  great  mathe- 
maticians have  thought  they  had  solved  difficult  problems,  poets  that 
they  had  composed  stanzas  of  force  and  beauty ;  but  these,  on  a  mo- 
ment's reflection,  they  have  discovered  to  be  an  inconsequent  flow  of 
ideas,  and  mere  nonsense.  A  few  exceptions  undoubtedly  have  occur- 
red, as  in  the  case  of  Mr.  Coleridge,  who  affirms  that,  under  these  cir- 
cumstances, he  composed  Kublai  Khan,  and  remembered  it  in  part  on 
awaking.  The  French  mathematician,  Condorcet,  makes  the  same  state- 
ment with  respect  to  several  of  his  writings. 

One  of  the  most  extraordinary  phenomena  presented  in  the  dreaming 
instantaneous  state  is  the  instantaneous  manner  in  which  a  long  series  ot 
aTo^g'trainof  events  mav  be  offered  to  the  mind,  the  exciting  cause  being 
events.  truly  of  only  a  momentary  duration.  Some  sudden  noise 


FORGETFULNESS   OF   DREAMS.  557 

arouses  us,  and,  in  the  act  of  waking,  a  long  drama  connected  with  that 
noise  appears  before  us  ;  or,  in  like  manner,  we  are  disturbed  perhaps  by 
a  flash  of  lightning,  and  with  that  flash  occurs  a  dream  which  seems  to 
us  to  occupy  a  space  of  hours  or  even  days,  so  many  are  the  incidents 
with  which  it  is  filled.  It  has  long  been  known  that  a  like  peculiarity 
has  offered  itself  to  those  who  have  suffered  by  drowning,  and  have  been 
subsequently  restored.  They  have  related  that  in  their  moment  of  su- 
preme agony,  the  whole  series  of  events  of  their  past  life  has,  as-  it  were, 
flowed  in  an  instant  upon  them  with  the  most  appalling  vividness,  their 
good  and  evil  works,  and  even  the  most  trifling  incidents  presenting 
themselves  with  distinctness — a  tide  of  memory.  And  doubtless  it  is 
owing  to  like  causes  that,  under  the  influence  of  opium  or  other  narcotic 
drugs,  the  relations  of  space  and  time  are  so  totally  destroyed  that  we 
seem  to  live  through  a  century  in  a  single  night,  or  to  take  in  our  view 
scenery,  the  distances  and  magnitudes  of  which  are  utterly  beyond  the 
reach  of  mortal  vision.  It  has  been  truly  said  that  the  province  of 
dreams  is  one  of  intense  exaggeration.  It  is  so  in  a  double  sense,  for 
with  equal  facility  we  spread  out  a  single  and  perhaps  in-  The  g  readin(r 
significant  circumstance,  so  that  it  occupies  the  entire  night,  of  one  idea  over 
or  we  crowd  a  thousand  strange,  though  perhaps  connected,  a  ong  time' 
representations  into  the  twinkling  of  an  eye.  Nor  is  it  by  any  means 
the  least  extraordinary  part  of  these  wonderful  facts  that  the  mind  occu- 
pies itself  in  an  undiverted  and  unbroken  manner  for  so  long  a  time, 
with  an  insignificant  idea  in  the  one  case,  and  perceives,  with  miraculous 
perspicuity,  the  rapidly  disappearing  occurrences  in  the  other ;  that  of  a 
majority  of  dreams  it  retains  no  precise  recollection,  though  they  may 
have  been  presented  with  an  intense  energy,  as  we  are  assured  from  the 
impression  of  dread  or  melancholy,  or  even  the  physical  results  they 
have  left,  as  when  we  awake  and  feel  the  heart  throbbing  Forgetfuiness 
violently  and  the  whole  frame  trembling  with  terror,  yet  can  of  dreams, 
not,  with  the  utmost  exertion  of  memory,  recollect  what  it  wds  that  we 
saw.  The  remembrance  of  dreams  by  no  means,  therefore,  depends  on 
the  intensity  of  the  impression  that  they  made  for  the  time ;  doubtless 
the  majority  of  them  are  forgotten  and  can  never  be  recalled.  In  some 
instances,  which  almost  every  one  can  recall,  we  dream  a  second  time  the 
same  dream  which  we  failed  to  remember  when  awake,  and,  it  is  said, 
even  occasionally  dream  that  we  are  dreaming. 

Our  mental  capability  for  recalling  the  scenes  that  have  occupied  us 
in  our  sleep  is  therefore  dependent  upon  something  more  than  the  depth 
of  the  impression  they  have  made.  Whether  it  be,  as  some  suppose, 
through  an  inertness  of  the  mind,  an  incapability  or  indisposition  of  pay- 
ing attention  to  the  things  thus  presented  to  it,  or  whether  it  be  that, 
through  accidental  causes,  the  vestiges  of  impressions  remaining  in  the 


558  SOMNAMBULISM. 

optic  thalami  are  brought  out  sometimes  with  more  and  sometimes  with 
less  force,  there  is  every  grade  of  intensity  presented,  from  those  floating 
indistinct  aerial  scenes,  which  seem  scarcely  to  leave  the  slightest  trace 
behind  them,  to  those  which,  in  spite  of  their  outraging  all  reality,  and 
even  all  probability,  leave  us  in  a  horror-stricken  state ;  such  as,  for  ex- 
ample, the  celebrated  dream  of  the  Emperor  Caligula,  in  which  he  thought 
that  the  sea  spoke  to  him.  Yet  there  can  be  no  doubt  that  in  all  these 
cases,  no  matter  how  indistinct  or  energetic,  how  false  or  how  true,  hoAV 

d*  i  n  un  narmon^ous  as  a  whole,  or  how  contradictory  and  grotesque, 
der  which  the  elements  of  which  all  dreams  are  composed  are  impres- 
dreams  arise.  g'ons  Q£  ^ings  that  we  have  seen  or  heard,  or  which  have 
been  otherwise  submitted  to  the  senses,  the  traces  of  which  still  remain 
imprinted  in  the  registering  ganglia  of  the  brain.  During  the  day,  while 
we  are  exposed  to  light,  and  sounds,  and  other  sources  of  disturbance,  the 
impressions  arising  therefrom  totally  overpower,  by  reason  of  their  new- 
ness and  intensity,  these  ancient  residues,  so  that  the  attention  of  the 
mind,  in  a  state  of  health,  is  never  directed  to  them ;  but  when  we  close 
our  eyes  in  the  silence  of  night,  all  such  external  impressions  are  at  an 
end,  the  organs  of  sense,  sight,  hearing,  smell,  and  touch,  are  successive- 
ly benumbed,  and  there  is  nothing  to  prevent  the  mind  thus  separated 
from  outer  things  from  occupying  itself  with  these  old  impressions,  any 
one  or  more  of  which,  through  accidental  circumstances,  presents  itself 
in  vigor,  and  a  dream  is  the  result. 

The  phenomena  of  dreams  therefore  illustrate,  in  a  significant  manner, 
the  remarks  that  we  have  made  respecting  the  functions  of  the  cephalic 
ganglia  of  insects  as  magazines  for  the  registry  of  impressions  received 
by  the  organs  of  sense.  No  explanation  of  dreaming  can  be  possibly 
given  without  admitting  for  a  part  of  the  human  brain  a  like  duty.  The 
important  advantages  which  accrue  to  our  physiological  explanations  of 
the  action  of  the  human  mind  from  the  admission  of  this  doctrine  have 
already  been  dwelt  upon. 

Connected  with  dreams,  and  being,  indeed,  a  dream  carried  into  action, 
Somnambu-  ig  somnambulism,  or  sleep-walking,  of  which  there  are  several 
iism.  grades,  from  mere  sleep-conversation  and  sleep-crying  to  the 

actual  performance  of  difficult  and  even  hazardous  feats.  The  young  in- 
fant evinces  its  discomforts  by  crying  in  its  slumber,  yet  it  can  be  com- 
forted without  awaking  by  the  well-known  voice  of  its  mother.  Chil- 
dren often  show  a  propensity  to  talking  in  their  sleep,  and  can  sometimes 
be  brought  to  give  a  few  rational  replies  to  inquiries  put  to  them.  At 
their  time  of  life,  the  disposition  is  more  frequently  manifested  to  get  out 
of  bed  and  move  about  the  house,  or  even  out  into  the  open  air  under  the 
influence  of  a  dream.  When  sleep-walking  occurs  in  the  adult,  it  is  lia- 
ble to  be  accompanied  by  actions  of  an  apparently  connected  kind,  though 


NIGHTMARE.  559 

their  object  may  be  quite  trivial,  and  in  its  attainment  considerable  risks 
may  be  run.  In  these  cases  it  seems  as  if  the  mind  was  absolutely  wrap- 
ped up  in  one  idea,  and  wholly  unable  to  comprehend  any  thing  else.  If 
the  eyes  of  the  somnambulist  are  wide  open,  he  sees  nothing,  and  even 
though  a  bright  light  be  presented  before  him,  the  iris  will  not  contract, 
yet  he  moves  about  in  a  manner  as  if  he  were,  in  one  respect,  guided  by 
understanding,  the  air  of  his  movements  being  as  if  he  knew  what  he 
was  about,  yet  in  another  respect  as  though  he  was  impelled  by  the 
most  unaccountable  folly,  walking  along  the  roof  of  the  house,  seating 
himself  on  the  chimney,  and  finding  his  way  in  safety  over  precipitous 
places,  past  which  it  would  be  impossible  he  should  go  if  awake,  no  mat- 
ter how  steady  his  head  might  be.  Besides  this  complete  condition  of 
somnambulism  there  are  intermediate  forms,  during  which  the  various 
senses  of  seeing,  hearing,  etc.,  are  in  partial  activity.  There  are  also 
differences  in  the  intensity  or  depth  of  the  state,  as  is  shown  by  the  ease 
or  difficulty  with  which  the  individual  is  aroused ;  sometimes  to  speak 
to  him  is  enough,  sometimes  he  must  be  violently  shaken  or  otherwise 
roughly  treated.  It  has  been  observed  in  some  cases  that  where  the  pa- 
tient spontaneously  wakens  under  circumstances  that  affright  him,  he  is 
at  once  broken  of  the  habit. 

With  dreams  and  somnambulism  is  also  to  be  classed  that  sensation 
which  often  surprises  and  disturbs  us  when  we  are  just  passing  Sensation 
into  sleep,  a  sensation  as  though  we  were  suddenly  falling  down  of  fallins- 
stairs.  This,  with  some  persons,  is  of  almost  nightly  occurrence.  Its 
opposite,  an  inability  to  move,  as  though  we  were  oppressed  by  some 
great  weight,  or  spell-bound  in  some  incomprehensible  way,  is  nightmare. 
In  this  distressing  affection  there  is  a  sense  of  oppression  at  Nightmare : 
the  epigastrium,  and  a  difficulty,  or  rather  impossibility,  of  its  causes- 
moving  or  speaking.  A  frightful  dream,  in  which  some  alarming  object 
is  depicted  with  intolerable  distinctness,  accompanies  these  symptoms, 
the  attack  terminating  by  a  struggle  to  shake  off  the  object  of  dread,  or 
to  escape  by  flight,  or  to  speak.  On  awaking,  the  sufferer  finds  himself 
trembling  with  terror,  the  respiration  hurried,  and  the  heart  throbbing 
violently.  The  intellectual  faculties  are  on  different  occasions  in  vari- 
ous states  of  activity,  and  sometimes  the  dream,  and  our  actions  conse- 
quent upon  it,  offer  no  violation  of  reason.  Indeed,  some  individuals  are 
affected  by  this  trouble  during  the  daytime,  when  they  are  wide  awake 
and  perfectly  aware  of  what  is  going  on ;  but,  whether  it  occurs  by  night 
or  by  day,  the  sentiment  with  which  it  oppresses  is  that  of  unspeakable 
dread.  Even  at  night  we  sometimes  are  conscious  of  its  approach,  when 
we  are  in  the  intermediate  state  between  sleeping  and  waking. 

The  cause  of  nightmare,  in  all  its  variety  of  forms,  is  disturbance  of 
the  respiratory  function,  which,  by  interfering  with  the  arterialization  of 


560  OF   DEATH. 

the  blood,  affects  the  brain.  This  disturbance  may  be  brought  on  in 
many  ways,  as  by  the  pressure  of  the  stomach  after  a  hearty  supper,  or 
in  diseased  conditions,  such  as  hydrothorax ;  but  it  is  popularly  supposed, 
where  these  morbid  conditions  are  not  obviously  concerned,  to  be  attrib- 
uted to  sleeping  on  the  back.  Though-  this  is  undoubtedly  true  in  a 
great  many  instances,  it  is  very  far  from  being  an  essential  condition,  for 
nightmare  may  occur  in  any  position  that  the  sleeper  may  possibly  as- 
sume. The  restraint  upon  the  arterialization  of  the  blood,  which  appears 
to  be  its  essential  condition,  interferes  with  the  circulation  through  the 
lungs  on  the  principles  that  have  been  described  in  a  preceding  chapter, 
nor  can  the  heart  force  a  passage,  however  violently  it  may  throb.  The 
effect  depends  not  so  much  upon  the  apparent  rate  and  power  with  which 
the  respiration  is  going  on,  for  any  embarrassment  or  difficulty  in  the  in- 
troduction of  air  merely  leads  to  snoring,  which  is  in  no  manner  connected 
with  nightmare.  The  cause  of  this  latter  affection  is  to  be  sought  for  in 
the  air-cells,  which  are  unable  to  rid  themselves,  with  their  accustomed 
facility,  of  the  carbonic  acid  and  other  effete  products  of  respiration  which 
they  contain. 

2D.   OF   DEATH. 

At  all  periods  of  life,  the  functional  activity  of  the  system  occasions  a 
Condition  of  waste  °^  ^s  tissues  by  the  interstitial  death  of  their  parts,  and 
healthy  equi-  therefore  involves  a  necessity  of  repair.  So  long  as  the  repa- 
ration balances  the  waste,  a  healthy  equilibrium  is  maintained ; 
but  when  the  nutritive  powers  decline,  as  old  age  approaches,  a  gradual 
deterioration  of  the  system  ensues. 

The  period  of  greatest  activity  is  also  that  of  greatest  waste,  and  of 
the  most  active  and  perfect  repair,  interstitial  death  and  the  removal  of 
decayed  material  then  occurring  in  the  most  rapid  manner.  The  energy 
of  life  is  thus  dependent  on  the  amount  and  completeness  of  death. 

At  a  later  period,  with  advancing  years,  although  the  loss  of  substance 
through  functional  activity  may  be  lessened,  the  renewal  and  restoration 
of  the  portions  which  are  necessarily  consumed  are  far  more  than  corre- 
spondingly diminished.  We  thus  become  incapacitated  corporeally  and 
mentally,  and,  if  no  accident  intervenes,  we  die  through  mere  old  age. 

On  several  occasions  we  have  already  noticed  the  analogy  between  the 
Death  of  a  ^Q  °f  individuals  and  that  of  species.  An  analogy  also  may 
molecule,  of  an  "j^  traced  in  the  circumstances  and  causes  of  their  death,  for 

individual  or-,-.  ,,  1111  11  t 

ganism,ofa  the  discoveries  of  geology  abundantly  show  that  thousands 
species.  Of  species  jn  the  organic  series  have  become  extinct.  The 

death  of  a  constituent  molecule  in  an  animal  body,  the  death  of  the  in- 
dividual animal  itself,  the  death  of  the  species  to  which  it  belongs,  are 
all  philosophical  facts  of  the  same  kind,  though  presenting,  perhaps,  in 


GEADUAL   DEATH.  561 

their  aspect  a  difference  of  interest  and  importance.     The  death  of  indi- 
viduals, as  has  been  said,  may  occur  in  two  ways,  by  acci-  Death  from  ac_ 
dent  or  by  old  age.    But  death  from  old  age  is  very  unusual,  cident  and  by 
for  even  in  the  cases  of  those  who  are  very  far  advanced  in  ° 
life,  its  close  is  ordinarily  brought  about  by  some  lesion  or  derangement 
of  the  vital  organs,  thus,  in  reality,  constituting  accidental  death. 

Most  men  desire  that  their  final  scene  may  be  attended  with  as  little 
derangement  as  possible  of  their  ordinary  mental  powers,  and 

*.  *,  .  .        Euthanasia. 

that  it  may  be  very  brief.  If  this  constitute  the  euthanasia, 
or  happy  death,  it  certainly  can  not  be  thought  that  extreme  old  age  is 
desirable,  constituting,  as  it  does,  a  long-continued  and  dreary  disease. 
The  senses  fail  us  in  the  same  manner  and  in  the  same  order  that  they 
do  when  we  are  falling  asleep,  their  gradual  deterioration  bringing  us  back 
to  the  helplessness  and  imbecility  of  infancy.  In  the  long  interval  dur- 
ing which  this  is  going  on,  the  aged  man  is  not  only  a  burden  to  himself, 
but  a  sad  spectacle  to  every  one  around  him ;  his  perceptions  arc  being 
gradually  blunted  ;  and  though  he  is,  as  it  were,  by  degrees  passing  into 
a  final  slumber,  it  is  in  that  disturbed  way  which  all  have  experienced  when 
they  fall  asleep  after  severe  fatigue. 

The  different  portions  of  the  body  die  in  succession :  the  system  of 
animal  life  before  that  of  organic,  and  of  the  former  the  sens-  f 

.-.,_  ,  .  ...  Gradual  death. 

ory  functions  fail  first,  voluntary  motion  next,  while  the  pow- 
er of  muscular  contraction  under  external  stimulus  still  feebly  continues. 
The  blood,  in  gradual  death,  first  ceases  to  reach  the  extremities,  its  pulsa- 
tions becoming  less  and  less  energetic,  so  that,  failing  to  gain  the  periph- 
ery, it  passes  but  a  little  way  from  the  heart ;  the  feet  and  hands  become 
cold  as  the  circulating  fluid  leaves  them,  the  decline  of  temperature  gradu- 
ally invading  the  interior.  No  one  has  ever  yet  offered  a  more  accurate 
picture  of  the  appearance  of  the  dying  than  that  presented  by  Hippocrates : 
"  If  the  patient  lies  on  his  back,  his  arms  stretched  out,  and  his  legs 
hanging  down,  it  is  a  sign  of  great  weakness ;  when  he  slides  down  in 
the  bed  it  denotes  death.  If,  in  a  burning  fever,  he  is  continually  feel- 
ing about  with  his  hands  and  fingers,  and  moves  them  up  before  his  face 
and  eyes  as  if  he  were  going  to  take  away  something  before  them,  or  on 
his  bed-covering  as  if  he  was  picking  or  searching  for  little  straws,  or 
taking  away  some  speck,  or  drawing  out  little  flocks  of  wool,  all  this  is 
a  sign  that  he  is  delirious,  and  that  he  will  die.  When  his  lips  hang 
relaxed  and  cold,  when  he  can  not  bear  the  light,  when  he  sheds  tears 
involuntarily,  when,  dozing,  some  part  of  the  white  of  the  eye  is  seen,  un- 
less he  usually  sleeps  in  that  manner,  these  signs  prognosticate  danger. 
When  his  eyes  are  sparkling,  fierce,  and  fixed,  he  is  delirious,  The  Hippo- 
or  soon  will  be  so ;  when  they  are  deadened,  as  it  were,  with  cratic  face- 
a  mist  spread  over  them,  or  their  brightness  lost,  it  presages  death  or 


562  THE   AGONY. 

great  weakness.  When  the  patient  has  his  nose  sharp,  his  eyes  sunk, 
his  temples  hollow,  his  ears  cold  and  contracted,  the  skin  of  his  forehead 
tense  and  dry,  and  the  color  of  his  face  tending  to  a  pale  green  or  leaden 
tint,  one  may  give  out  for  certain  that  death  is  very  near,  unless  the 
strength  of  the  patient  has  been  exhausted  all  at  once  by  long  watchings, 
or  by  a  looseness,  or  being  a  long  time  without  eating." 

Even  after  death  some  of  the  organic  functions  continue  for  a  time, 
Post-mortem  more  particularly  secretion  and  the  development  of  heat.  In 
t^nT^d^as-  a  *°rmer  chapter,  page  444,  the  capability  of  extraordinary 
sions.  muscular  motions  has  been  referred  to.  From  other  inter- 

esting observations  on  those  who  have  been  instantaneously  decapitated 
by  the  guillotine,  it  has  been  asserted  that  the  body  can  display  what 
has  been  termed  post-mortem  passion  and  resentment.  It  may,  however, 
be  doubted  whether  this  is  really  true.  Perhaps  these  effects  are  only 
analogous  to  those  convulsive  manifestations  which  may  be  easily  pro- 
duced, in  an  intensely  interesting  way,  by  the  application  of  voltaic  bat- 
teries to  those  who  have  been  dead  for  some  time. 

Physiologists  often  quote  the  sentiment  of  Montaigne,  "  With  how 
insensibilit  IM6  anxiety  do  we  lose  the  consciousness  of  light  and  of 
before  the  final  ourselves."  By  this  they  would  convey  the  idea  that  the 
act  of  dying  is  as  painless  as  the  act  of  falling  asleep,  and 
also  as  little  perceived.  They  recall  the  fact  which  seems  to  support 
this  view,  that  those  who  have  been  recovered  after  apparent  death  from 
drowning,  and  after  sensation  has  been  totally  lost,  report  that  they  have 
experienced  no  pain  ;  and,  indeed,  when  we  reflect  that  the  sensory  pow-' 
ers  are  the  first  to  decline,  the  eye  and  the  ear,  at  an  early  period  in  the 
article  of  death,  failing  to  discharge  their  duty,  and  the  general  sense  of 
touch  becoming  rapidly  more  and  more  obtuse,  we  can  scarcely  put  any 
otner  interpretation  upon  the  final  struggles  which  constitute  what  is  so 
significantly  called  the  agony,  than  that  they  are  purely  automatic  and 
therefore  unfelt.  Doubtless  the  mind,  in  this  solemn  moment,  is  some- 
times occupied  with  an  instantaneous  review  of  impressions  long  before 
made  upon  the  brain,  and  which  offer  themselves  with  clearness  and 
energy  now  that  present  circumstances  are  failing  to  excite  its  attention, 
through  loss  of  sensorial  power  of  the  peripheral  organs,  this  state  of 
things  having  also  been  testified  to  by  those  who  have  been  recovered 
from  drowning. 

Life  closes  at  last  in  various  ways.  Some  pass  away  as  though  they 
were  really  falling  asleep  ;  others  with  a  deep  sigh  or  groan ;  others  with 
a  gasp ;  and  some  with  a  convulsive  struggle. 


DIFFERENCES    IN   MEN. 


563 


CHAPTER  VII. 

ON  THE  INFLUENCE  OF  PHYSICAL  AGENTS  ON  THE  ASPECT  AND  FORM 
OF  MAN  AND  ON  IHS  INTELLECTUAL  QUALITIES. 

Differences  in  Form,  Habits,  and  Color  of  Men. — Ideal  Type  of  Man. — Its  Ascent  and  Descent. 
^-Causes  of  these  Variations. 

Doctrine  of  the  Unity  of  the  Human  Race. — Doctrine  of  its  Origin  from  many  Centres. 

Influence  of  Heat  on  Complexion. —  Cause  of  Climate  Variations. — Influence  of  Heat  illustrated 
by  the  cases  of  the  Indo-Europeans,  the  Mongols,  the  American  Indians,  and  the  Africans. — 
Distribution  of  Complexion  in  the  Tropical  Races. 

Variations  in  the  Skeleton. — Four  Modes  of  examining  the  Skull. —  Connection  of  the  Shape  of 
the  Skull  and  Manner  of  Life. — Physical  Causes  of  Variation  of  the  Skull. 

Influence  of  the  Action  of  the  Liver  on  Complexion. — Influence  of  the  Action  of  the  Liver  on  the 
Form  of  the  Skull. — Base  Form  of  Skull  arising  from  Low  as  well  as  High  Temperatures. — 
Disappearance  of  the  Red-haired  and  Blue-eyed  Men  in  Europe. 

The  Intellectual  Qualities  of  Nations. — Synthetical  Mind  of  the  Asiatic. — Analytical  Mind  of  the 
European. —  Their  respective  Contributions  to  Human  Civilization. — Spread  of  Mohammedan- 
ism in  Africa. — Spread  of  Christianity  in  America. — Manner  of  the  Progress  of  all  Nations 
in  Civilization. 

THERE  are  great  differences  in  the  aspect  of  men. 

The  portrait  of  Newton  is  from  the  frontispiece  of  his  immortal  Prin- 

Fifj.  266.  cipia.       "  Does    he    eat,    Differences  in 

and   drink,  and   sleep,  £™*0"fd 
like  other  people  ?"  ask-  men. 

Fig.  207. 


Sir  Isaac  Newton.  Australian. 

ed  the  Marquis  de  I'Hopital,  himself  a  great  contemporary  French  math- 


564  •  DIFFERENCES    IN   MEN. 

ematician:  "  I  represent  him  to  myself  as  a  celestial  genius  entirely  dis- 
engaged from  matter."  And,  truly,  transcendent  intellect  shines  out  in 
every  lineament  of  that  noble  countenance. 

What  a  contrast  between  the  astronomer,  of  whom  the  human  race 
may  be  justly  proud,  and  the  Australian  savage  whose  portrait  Dr.  Prich- 
ard  has  furnished!  This  man  lives  in  a  hollow  tree,  which  he  has  in 
part  excavated  by  fire,  and  obtains  a  precarious  support  from  shell-fish, 
or  bruised  ants  and  grass.  He  can  make  a  hook  of  a  piece  of  oyster, 
and  can  fasten  a  line  to  it.  He  is  lost  in  filth  and  vermin.  His  life  is 
like  that  of  a  beast ;  it  is  concerned  only  with  to-day.  The  early  navi- 
gators accused  him  of  cannibalism.  We  can  not  say  that  his  features 
acquit  him  of  the  charge. 

History  teaches  us  that  a  nation  may  pass  through  an  ascending  or 
descending  career.  It  may,  by  long-continued  mental  culture,  exhibit  a 
general  mental  advance,  and  under  such  circumstances  may  produce,  here 
and  there,  an  intellect  of  the  first  order ;  or  it  may  go  through  a  course 
of  degradation  until  it  reaches  conditions  inconsistent  with  its  continued 
existence,  and  then  it  dies  out. 

Man  is  accordingly  distributed  over  the  face  of  the  earth  in  various  con- 
Fig.  268.  ^bls^  ditions.     Here  he  presents 

the  civilization  of  the  Euro- 
pean, there  the  abject  mise- 
ry of  the  Australian.  What 
more  humiliating  spectacle 
could  be  offered  to  us  than 
the  annexed  engraving,  Fig- 
ure 268,  from  M.  d'Urville? 
Even  a  negro  of  Guinea 
might  look  down  on  such  a 
specimen  of  human  imbecil- 
ity and  physical  weakness 
with  contempt,  and  refuse 
to  recognize  such  a  being  as 
a  man  at  all. 

Wrhat  is  it  that  has 
brought  this  man  and  his 
companion  to  such  a  pass? 

Australians.  .  An  almost   tropical  sun,  a 

Causes  of  these  pestilential  climate,  starvation,  nakedness,  the  want  of  shel- 
differences.  ter,  personal  fear :  these  have  done  their  work  on  the  suc- 
cessive generations  of  his  miserable  ancestors,  who  have  been  forced  from 
step  to  step  in  a  descending  career,  and  here  is  the  result. 

Among  the  causes  which  influence  the  aspect  of  man,  there  are  two 


IDEAL   TYPE    OF   MAN.  565 

which  are  pre-eminent :  heat  determines  his  complexion ;  social  condi- 
tion the  form  of  his  Tbrain,  and,  therefore,  that  of  his  skull. 

The  aspect  of  man  in  form  and  color  oscillates  between  two  extremes. 
Submitted  for  a  due  time  to  a  high  temperature,  any  race,  Ascenfc  and  de 
irrespectively  of  its  original  colos,  will  become  dark ;  or  if  to  scent  of  human 
a  low  temperature,  it  will  become  fair.  Under  such  condi-  orsaniz 
tions  as  will  be  set  forth  in  this  chapter,  it  will  pass  to  the  elliptical ;  un- 
der others,  to  the  prognathous  form  of  skull.  No  race  is  in  a  state  of 
absolute  equilibrium,  or  able  successfully  to  maintain  its  present  physi- 
ognomy, if  the  circumstances  under  which  it  lives  undergo  a  change.  It 
holds  itself  ready,  with  equal  facility,  to  descend  to  a  baser,  or  rise  to  a 
more  elevated  state,  in  correspondence  with  those  circumstances. 

I  think  that  this  principle  has  not  been  recognized  with  sufficient  dis- 
tinctness by  those  who  have  studied  the  natural  history  of  man.  They 
have  occupied  themselves  too  completely  with  the  idea  of  fixity  in  the 
aspect  of  human  families,  and  have  treated  of  them  as  though  they  were 
perfectly  and  definitely  distinct,  or  in  a  condition  of  equilibrium.  They 
have  described  them  as  they  are  found  in  the  various  countries  of  the 
globe,  and  since  these  descriptions  remain  correct  during  a  long  time,  the 
general  inference  of  an  invariability  has  gathered  strength,  until  some 
writers  are  to  be  found  who  suppose  that  there  have  been  as  many  sep- 
arate creations  of  man  as  there  are  races  which  can  be  distinguished  from 
each  other.  We  are  perpetually  mistaking  the  slow  movements  of  Na- 
ture for  absolute  rest.  "We  confound  temporary  equilibration  with  final 
equilibrium. 

Man  can  not  occupy  a  new  climate  without  an  organic  change  occur- 
ring in  his  economy,  which  by  degrees  comes  to  a  corre-  Corres  on(jence 
spondence  with  the  conditions  by  which  it  is  surrounded,  of  climate  and 
In  this  career,  each  individual,  as  a  member  of  one  genera-  organi 
tion$  may  only  make  a  partial  advance,  for  differentiation  most  commonly 
occurs  in  the  early  periods  of  embryonic  life,  as  described  at  page  505; 
but,  since  all  individual  peculiarities  are  liable  to  hereditary  transmission, 
the  cumulative  effect  becomes  strongly  marked  at  last.  So  dominating 
is  the  control  which  physical  influences  exert  over  us,  that  invariability 
of  our  aspect  for  several  generations  may  be  received  as  a  proof  that  those 
influences  have  been  stationary  in  kind  and  degree.  In  such  a  perfect 
manner  is  that  aspect  dependent  on  them  that  it  is  truly  their  represent- 
ative. If  they  change,  it  must  change  too. 

I  do  not,  therefore,  contemplate  the  human  race  as  consisting  of  vari- 
eties, much  less  of  distinct  species,  but  rather  as  offering  numberless  rep- 
resentations of  the  different  forms  which  an  ideal  type  can  be  made  to  as- 
sume under  exposure  to  different  conditions.  I  believe  that  that  ideai  type 
ideal  type  may  still  be  recognized,  even  in  cases  that  offer,  when  of  man- 


566  HABITS   OF   NATIONS. 

compared  together,  complete  discordances  ;  and  that,  if  such  an  illustra- 
tion be  permissible,  it  is  like  a  general  expression  in  algebra,  which  gives 
rise  to  different  results  .according  as  we  assign  different  values  to  its 
quantities,  yet  in  every  one  of  those  results  the  original  expression  exists. 

From  this  it  therefore  follows  that  there  is  a  capability  of  metamor- 
phosis or  transmutation  from  form  to  form  ;  that  the  human  system  pos- 
sesses no  inherent  resistance  to  change,  no  physiological  inertia,  but  will 
pass  indifferently  upward  and  downward,  toward  perfection  or  toward 
degradation,  as  circumstances  overrule,  yet  is  it  the  same  human  system 
throughout.  Nor  is  it  of  any  consequence  that  the  progress  of  these 
re  uired  cnanSes  ma7  ^e,  as  we  term  them,  tardy,  and  that  for  their 
for  physiolog-  completion  a  long  time  may  be  required.  Even  a  mass  of 

change,  inorganic  matter  —  a  rock  —  transferred  from  the  equator 
toward  the  pole,  or  from  the  pole  to  the  equator,  would  not  change 
its  temperature  to  that  of  the  new  locality  at  once ;  it  would  come  to 
its  destined  equilibrium  in  a  gradual  way,  in  a  time  depending  en  its 
mass  and  conducting  power.  We  should  not  impute  its  slow  manner 
of  yielding  to  any  inherent  principle  of  resistance  which  it  possessed. 
The  physiological  metamorphosis  of  man  is  an  affair  of  centuries.  The 
universal  recognition  of  the  principle  that  such  changes  are  possible  lies 
at  the  bottom  of  all  our  attempts  to  elevate  communities  by  ameliorating 
their  social  condition  and  by  education. 

In  the  remarks  which  follow,  it  will  therefore  be  understood  that  I  re- 
ceive the  classifications  of  Blumenbach  and  other  authors  as  offering  a 
convenience  in  description,  but  do  not  attach  to  them  any  essential  sig- 
nificance. 

Though  plants  and  animals  are  limited  to  certain  localities  of  the  earth's 
Habits  of  dif-  surface,  some  species  being  formed  in  one  and  some  in  an- 
ferent  nations.  Other  region,  the  human  family  lives  indifferently  all  over  the 
surface  of  the  globe.  It  occupies  countries  where  the  thermometer  falls 
to  50°  below  zero,  or  where  the  temperature  of  the  midday  sun  is  160°. 
In  these  different  climates,  the  most  marked  differences  in  color,  stature, 
conformation,  and  habits  are  exhibited,  there  being  every  shade,  from 
a  jet  black  to  a  fair  white ;  every  stature,  from  the  pigmy  Esquimaux 
and  Laplanders  to  the  tall  Patagonian  ;  every  variety  of  facial  angle,  from 
that  acute  one  which  characterizes  the  ape  to  the  classical  aspect  of  the 
Greek,  which  is  more  than  90°  ;  every  pursuit  of  life,  hunting,  fishing, 
the  keeping  of  flocks,  agriculture,  commerce,  and  the  arts  of  civilized  so- 
ciety. To  these  might  be  added  the  use  of  every  variety  of  food,  from  a 
wretched  subsistence  on  worms  and  roots  scratched  out  of  the  ground  to 
the  luxurious  habits  of  the  epicure  ;  every  grade  of  locomotion,  from 
those  who  never  leave  the  hill  or  valley  where  they  were  born  to  those 
who  are  perpetually  wandering  all  over  a  continent,  nay,  even  all  over 


REALMS  OF  PLANTS  AND  ANIMALS.  567 

the  globe.  There  might,  too,  be  added  every  variety  of  character  and 
every  degree,  of  intellectuality.  Among  these  differences,  the  variations 
of  language  are  by  no  means  the  least  important.  It  is  estimated  that 
more  than  three  thousand  dialects  are  spoken. 

Among  these  races  certain  common  traditions  prevail,  historical  rem- 
iniscences handed  down  from  one  generation  to  another,  Traditions  of 
which  convey  the  deeds  of  former  great  men  who  have  either  Bations> 
distinguished  themselves  by  their  achievements  in  war  or  by  their  in- 
ventions in  the  peaceful  arts ;  traditions  which  have  also  communicated 
the  religion  or  the  superstition  of  the  ancient  times,  and  which,  among 
people  inhabiting  countries  remote  from  one  another,  present  such  an  as- 
pect of  sameness,  that  we  must  either  refer  them  to  one  common  and  more 
ancient  source,  or  regard  them  as  arising  from  analogous  peculiarities  in 
the  mental  structure  of  the  whole  race. 

There  can  not  be  a  doubt  that  in  the  lapse  of  many  ages  the  influ- 
ence of  external  physical  agents  must  have  made  a  marked  influenceofex 
impression  upon  the  original  characters  of  men.  Few  ques-  temai  agents 
tions  have  been  more  critically  discussed  than  the  extent  to  ° 
which  this  change  of  aspect  by  physical  agents  can  go,  many  naturalists 
believing  that  the  sole  cause  of  national  difference  is  the  influence  of  cli- 
mate or  temperature — an  influence  which  is  sufficient  to  account  for  all 
other  organic  peculiarities  we  have  just  specified ;  for  if  we  admit  that 
the  same  original  germ  may  develop  itself  into  countless  forms,  accord- 
ing as  it  has  been  exposed  to  different  physical  agents,  much  more  is  it 
probable  that  the  various  races  composing  the  human  family,  exposed  as 
they  have  been  to  different  physical  circumstances,  may  by  degrees  have 
assumed  the  discordant  features  they  present,  although  they  have  de- 
scended from  one  original  stock. 

Here  we  shall  have  to  consider  the  weight  which  should  be  attached 
to  a  very  remarkable  observation  which  has  of  late  been  Geographical 
made  as  respects  the  distribution  of  man.  -With  regard  to  'JSJ^'* 
plants,  it  has  long  been  known  that  they  are  grouped  round  mais,andman. 
certain  centres,  which  may  be  regarded  as  their  foci  of  origin,  and  one  of 
such  groups  compared  with  another  presents  striking  contrasts ;  the  veg- 
etation of  Central  Africa  is  wholly  distinct  from  that  of  Europe,  the  veg- 
etation of  Europe  distinct  from  that  of  North  America,  and  this,  again, 
from  New  Holland.  There  are  no  lauringe  in  Central  Africa,  no  heaths 
in  the  New  World.  The  forests  of  New  Holland  gain  their  most  strik- 
ing features  from  their  leafless  acacias  and  eucalypti.  So,  in  like  man- 
ner, there  are  foci  of  origin  and  circles  of  distribution  as  regards  animal 
life.  The  fauna  of  Asia  is  wholly  dissimilar  from  that  of  Europe,  the 
fauna  of  Europe  is  dissimilar  from  that  of  North  America,  and  this,  again, 
from  that  of  Africa  and  New  Holland.  Without  specifying  details,  we 


568  ORIGIN   OF   NATIONS. 

may  recall  that  the  hippopotamus  and  camelopard  are  natives  of  Africa, 
and  are  restricted  to  it ;  the  tiger  is  a  native  of  India ;  the  armadillos 
and  ant-eaters,  of  South  America ;  the  kangaroo  and  ornithorhynchus,  of 
New  Holland.  The  earth's  surface  might  thus  be  divided  into  regions 
or  realms,  each  possessing  its  own  special  flora  and  fauna.  And  more 
than  this,  the  oceans,  too,  might  in  like  manner  be  parted  off,  and  this 
not  only  as  regards  their  surface,  but  also  in  strata  at  different  depths. 
Now  these  botanical  centres  and  circles  are  coincident  with  the  zoological 
centres  and  circles,  and  hence  there  has  arisen  the  idea  that  such  centres 
have  been  truly  points  of  original  development,  both  for  one  and  the  oth- 
er of  these  natural  kingdoms,  and  that  the  globe  has  not  been  filled  by  a 
process  of  dispersion  or  diffusion  from  one  point,  but  co-ordinately,  and, 
perhaps,  contemporaneously  from  many  such  foci,  and  that  we  can  still 
recognize  the  position  of  these  foci  by  a  critical  study  of  animals  and 
plants. 

As  to  the  discussions  which  have  of  late  years  arisen  on  this  question, 
The  IAVO  hy-  the  reader  may  refer  to  the  work  of  Drs.  Nott  and  Gliddon 
orMrfof  nathe  on  ^ie  tvPes  °^  mankind  for  arguments  in  support  of  a  mul- 
tions.  titude  of  centres  of  human  origin,  and  to  that  of  Dr.  Prich- 

ard  on  the  natural  history  of  man  for  those  in  behalf  of  the  unity  of  the 
race.  In  these  works,  respectively,  will  be  found  most  of  the  facts  hith- 
erto brought  forward. 

In  the  former  of  these  works,  Professor  Agassiz  draws  attention  to  the 
Doctrine  of  circumstance  that  all  around  the  Arctic  circle,  and  therefore  in 
Professor  every  longitude,  is  to  be  found  one  race  offering  characters  that 
Agassiz.  are  strikingly  homogeneous  in  aspect,  intellect,  and  habits  of  life, 
represented  in  America  by  the  Esquimaux,  in  Europe  by  the  Laplanders, 
and  in  Asia  by  the  Samoiedes.  These  live  in  a  region  of  which  the 
Floral  faunai  ^auna  an(^  ^ora  are  likewise  homogeneous.  It  has  every  where 
and  human  '  the  same  dreary  expanses,  covered  with  dwarf  birches,  moss- 
es, and  lichens ;  .in  its  waters  there  are  the  same  fishes,  as 
the  salmon,  and  the  same  molluscs  and  echinoderms.  In  the  air  it  has 
the  same  birds.  Among  its  mammals  found  thus  with  uniformity,  the 
white  bear,  the  reindeer,  the  walrus,  and  the  whale  may  be  mentioned. 
With  a  special  fauna  thus  coinciding  with  a  special  flora,  there  is  also  a 
special  variety  of  man. 

What  has  here  been  said  respecting  Arctic  life  may  be  generalized. 
Each  of  the  coincident  floral  and  faunai  circles  has  its  own  species  of 
man. 

Thus,  in  the  temperate  zone,  may  be  distinguished  three  such  primary 
realms,  each  of  which  is  distinct  as  regards  its  botany  and  zoology ;  and, 
in  correspondence,  we  find  that  in  the  first,  in  the  country  of  the  Mongo- 
lians, to  the  east  beyond  the  Caspian  Sea,  there  are  nations  whose  com- 


HABITS  OF  NATIONS.  569 

plexion  is  yellow ;  in  the  second,  upon  the  shore  of  the  Mediterranean 
and  throughout  Europe,  there  are  others  whose  complexion  is  white ;  in 
the  third,  in  America,  others  whose  complexion  is  red;  and  though 
these  three  widely-extended  races  touch,  upon  their  north  boundary,  the 
homogenous  Arctic  inhabitants,  in  every  respect  they  may  be  distin- 
guished from  them.  The  temperature  of  the  zone  in  which  they  live 
ranges  from  32°  to  74° ;  it  permits  the  growth  of  pines,  nut  and  fruit 
trees,  and  among  its  animals  might  be  mentioned  the  bear,  the  wolf,  the 
otter,  the  deer,  the  squirrel,  and  the  rat;  these  animals,  however,  respect- 
ively exhibiting  striking  differences  characteristic  of  their  three  focal  cen- 
tres :  the  black  bear  belongs  to  North  America,  the  brown  bear  to  Europe, 
and  the  bear  of  Thibet  to  Asia.  The  European  stag  finds  its  American 
analogue  in  the  wapiti,  and  in  Asia  in  the  musk  deer.  The  wild  ox  of 
Lithuania  differs  from  the  North  American  buffalo,  and  this,  again,  from 
the  Mongolian  yak.  Even  among  plants  the  same  differences  may  be 
traced ;  the  pines  of  Europe  are  not  the  same  as  the  pines  of  America, 
and  thus  it  would  appear  that  each  of  the  three  great  organic  circles  be- 
longing to  the  temperate  zone  has  a  flora,  a  fauna,  and  a  human  species 
of  its  own. 

The  same  general  result  might  be  established  for  the  tropical  regions, 
and  special  centres  assigned  for  Africa,  Malaya,  and  Polynesia. 

In  view  of  this  distribution  as  connected  with  habits,  Dr.  Prichard  thus 
expresses  himself  in  his  Natural  History  of  Man :  "  Let  us  Habits  of  na- 
imagine,  for  a  moment,  a  stranger  from  another  planet  to  visit  tions- 
our  globe,  and  to  contemplate  and  compare  the  manners  of  its  inhabit- 
ants, and  let  him  first  witness  some  brilliant  spectacle  in-  one  of  the  high- 
ly-civilized countries  of  Europe :  the  coronation  of  a  monarch,  the  in- 
stallation of  St.  Louis  on  the  throne  of  his  ancestors,  surrounded  by  an 
august  assembly  of  peers,  and  barons,  and  mitred  abbots,  anointed  from 
the  cruise  of  sacred  oil  brought  by  an  angel  to  ratify  the  divine  privilege 
of  kings ;  let  the  same  person  be  carried  into  a  hamlet  in  Negroland,  in 
the  hour  when -the  sable  race  recreate  themselves  with  dancing  and  bar- 
barous music;  let  him  then  be  transported  to  the  saline  plains  over 
which  bald  and  tawny  Mongols  roam,  differing  but  little  in  hue  from  the 
yellow  soil  of  their  steppes,  brightened  by  the  saffron  flowers  of  the  iris 
and  tulip ;  let  him  be  placed  near  the  solitary  den  of  the  Bushman,  where 
the  lean  and  hungry  savage  crouches  in  silence  like  a  beast  of  prey,  watch- 
ing  with  fixed  eyes  the  creatures  which  enter  his  pitfall,  or  the  insects 
and  reptiles  which  chance  brings  within  his  grasp ;  let  the  traveler  be 
carried  into  the  midst  of  an  Australian  forest,  where  the  squalid  con> 
panions  of  kangaroos  may  be  seen  crawling  in  procession  in  imitation  of 
quadrupeds ;  can  it  be  supposed  that  such  a  person  would  conclude  the 
various  groups  of  beings  whom  he  had  surveyed  to  be  of  one  nature,  one 


570  RESEMBLANCES   OF  NATIONS. 

tribe,  or  the  offspring  of  the  same  original  stock  ?  It  is  much  more  prob- 
able that  he  would  arrive  at  an  opposite  conclusion." 

On  this  it  may  be  remarked  that  much  would  depend  on  the  previous 
training  of  the  illustrious  stranger.  If  his  mind  had  been  imbued  with 
a  better  philosophy  than  that  which  prevails  in  this  our  lower  world,  he 
might  look  with  an  equal  eye  on  the  transitory  fashions  before  him,  and 
penetrate  to  the  first  principles  of  things  through  the  false  glare  of  pomp 
or  through  debasement  and  degradation,  and  so  arrive  at  a  conclusion 
precisely  the  opposite  of  the  foregoing,  in  the  same  manner  as  has  Dr. 
Prichard  himself. 

For,  from  such  an  elevated  point  of  view,  the  plumed  pageant  of  civ- 
ilized life  might  only  appear  to  be  a  modified  phase  of  the  ceremonials 
of  equinoctial  Africa,  where  the  inhabitants,  on  their  festive  occasions, 
adorn  their  naked  bodies  with  leaves,  and  present  oblations  of  palm  oil 
with  many  genuflexions  to  their  chiefs  and  enchanters.  Beneath  the 
feathers  in  the  one  case,  and  the  leaves  in  the  other,  he  might  discern  the 
same  ruling  idea,  and  detect  the  same  human  nature ;  or,  if  his  vision 
could  reach  into  the  past,  and  recall  the  credulous  Greek  worshiping  be- 
fore the  exquisitely  perfect  statues  of  the  deities  of  his  country,  beseeching 
them  for  sunshine  or  for  rain,  and  then  turn  to  the  savage  Amaiman,  who 
commences  his  fasts  by  taking  a  vomit,  and,  for  want  of  a  better  goddess, 
adores  a  dried  cow's  tail,  imploring  it  for  all  earthly  goods,  and  particu- 
larly to  pay  his 'debts — again  the  same  principle  would  emerge,  only  il- 
lustrated by  the  circumstance  that  the  savage  is  more  thorough,  more 
earnest  in  his  work. 

In  fact,  wherever  we  look,  man  is  the  same.  Stripped  of  exterior  cov- 
Resembiances  erings,  there  is  in  every  climate  a  common  body  and  a  com- 
among  nations.  mon  mm(j.  Are  not  all  of  us  liable  to  the  same  diseases  ? 
Have  not  all  a  tendency  to  exist  the  same  length  of  time  ?  Is  it  the 
temperature  of  our  body,  the  beat  of  the  pulse,  the  respiration  that  we 
observe — are  they  not  every  where  alike  ?  Or,  turning  to  the  manifesta- 
tions of  the  mind,  is  there  not,  among  all  the  tribes  of  oui*  race,  a  belief 
in  the  existence  and  goodness  of  God  ?  in  unseen  agents,  intermediate 
between  him  and  ourselves  ?  and  in  a  future  life  ?  Do  we  not  all  put  a 
reliance  in  the  efficacy  of  prayers  ?  and  all,  in  our  youth,  have  a  dread  of 
ghosts  ?  How  many  of  us,  in  all  parts  of  the  world,  attach  a  value  to 
pilgrimages,  sacrificial  offerings,  fastings,  and  unlucky  days,  and  in  our 
worldly  proceedings  are  guided  by  codes  of  law  and  ideas  of  the  nature 
of  property !  Have  we  not  all  the  same  fears,  the  same  delights,  the 
same  aversions,  and  do  we  not  resort  to  the  use  of  fire,  domestic  animals, 
and  weapons  ?  Do  we  not  all  expect  that  the  differences  which  surround 
us  here  will  be  balanced  hereafter,  and  that  there  are  rewards  and  punish- 
ments ?  Is  there  not  a  common  interpretation  of  all  the  varied  forms  of 


LOCAL  TEMPERATURES.  571 

funeral  ceremonies?  a  common  sentiment  of  the  sacredness  of  the  tomb? 
Have  we  not  always,  and  do  we  not  every  where  set  apart  a  sacerdotal 
order,  who  may  mediate  for  us  ?  In  our  less  advanced  civilization,  do  we 
not  all  believe  in  sorceries,  witches,  and  charms  ?  It  signifies  nothing 
in  what  particular  form  our  mental  conceptions  are  embodied ;  it  is  the 
conception  that  concerns  us,  and  not  the  aspect  it  has  assumed.  Thus 
equally  do  the  views  of  the  various  nations  demonstrate  their  innate  be- 
lief of  a  future  world — the  undisturbed  Hunting-ground  of  the  American 
Indian,  the  voluptuous  Paradise  and  society  of  the  houris  of  the  Ara- 
bian, or  the  snow  hut  of  the  Esquimaux,  in  which  the  righteous  feed  on 
the  blubber  of  whales. 

Turning  our  attention  to  the  influence  of  temperature,  it  may  be  ob- 
served that  the  development  of  coloring  matter  in  the  skin  de-  influence  of 
pends  on  the  heat  to  which  we  are  exposed.  Generally,  it  ^JJIe'com^ 
might  therefore  appear  that  there  should  be  a  correspondence  piexion. 
between  the  complexion  and  the  latitude  of  the  place  of  our  abode,  the 
skin  being  darker  as  we  approach  the  equator,  and  fairer  toward  the 
poles,  because,  since  all  the  heat  that  we  receive  comes  from  the  sun, 
the  amount  which  is  furnished  to  us  depends  upon  the  obliquity  of  his 
rays,  and  therefore  upon  the  latitude.  But  this  is  true  only  in  a  very 
general  way,  and  many  exceptions  at  once  spontaneously  suggest  them- 
selves. I  may  point  out  some  of  these  variations. 

The  temperature  of  a  place  depends  on  three  leading  circumstances, 
its  latitude,  its  elevation  above  the  sea,  and  on  meteorolog-  causes  of  local 
ical  conditions.  Kespecting  the  latitude,  nothing  need  be  temperatures. 
added  to  the  remarks  already  offered ;  and  as  regards  the  influence  of 
elevation  above  the  sea,  it  is  to  be  remembered  that  there  is  a  decline  of 
temperature  as  we  ascend  in  the  atmosphere  from  any  point  of  the  globe, 
and  for  this  reason,  as  has  been  already  explained  at  page  473,  even  un- 
der the  equator  there  will  be  an  arrangement  answering  to  climates  on 
every  high  mountain,  its  top,  if  sufficiently  elevated,  being  covered  with 
perpetual  snow.  Of  meteorological  conditions,  it  may  be  said  that  they 
are  so  numerous  as  to  render  it  almost  impossible  to  give  a  full  and  yet 
brief  statement  of  them,  but  as  illustrations  may  be  mentioned  the  prox- 
imity of  the  sea,  or  of  great  desert  tracts,  ocean  currents,  the  prevailing 
winds  ;  thus,  in  our  hemisphere,  a  north  wind  predominating  lowers  the 
mean  temperature  of  the  place,  a  south  wind  tends  to  raise  it ;  and  thus, 
also,  the  great  desert  of  Sahara  and  the  American  Gulf  Stream  increase 
by  many  degrees  the  temperature  of  Europe. 

For  such  reasons,  therefore,  the  lines  of  equal  heat  do  not  correspond 
to  the  parallels  of  latitude,  but,  as  an  inspection  of  a  chart  of  them  will 
show,  deviate  greatly  therefrom. 

In  treating  of  the  influence  of  heat  on  plants,  it  was  shown  that,  when 


572  RELATIONS   OF   HEAT. 

we  make  our  examination  in  a  critical  manner,  the  problem  is  not  so  sim- 
ple as  appears  at  first  sight,  and  that  there  are  several  different  relations 
of  the  heat  which  must  be  considered.  Thus  the  geography  of  plants  is 
not  wholly  determined  by  the  mean  temperature  of  the  whole  year,  nor 
by  the  greatest  heat  of  the  summer,  nor  the  greatest  cold  of  winter ;  that 
is  to  say,  it  neither  follows  the  isothermal,  isotheral,  nor  isochimenal  lines. 
Moreover,  the  luxuriance  of  vegetation  is  not  so  much  dependent  upon 
the  temperature  or  intensity  of  heat  as  it  is  upon  the  quantity.  These 
remarks  apply  with  much  force  to  the  case  now  before  us, 

Intensity  and  jr.r  •/ 

quantity  of  for  the  change  of  complexion  is  not  so  much  dependent  upon 
heat  compared.  tte  intensitv  Of  lieat  determined  by  the  thermometer  as  it  is 
upon  the  absolute  annual  quantity ;  for,  though  these  conditions  of  in- 
tensity and  quantity  of  heat  are  essentially  distinct,  yet  it  will  generally 
happen  that  they  may  increase  or  diminish  together,  without  there  being 
an  absolute  correspondence  between  them.  There  can  be  no  doubt  that 
the  quantity  of  heat  annually  furnished  in  Guinea  vastly  exceeds  the 
quantity  annually  furnished  to  any  part  of  tropical  America.  It  is  upon 
this  condition,  and  not  upon  the  height  of  the  thermometer,  that  the  dark- 
ening of  the  human  complexion  depends. 

To  the  reader  who  is  not  familiar  with  the  technicalities  of  Natural 
Philosophy,  an  explanatory  illustration  of  the  statement  here  made  may 
be  of  value.  If  he  will  suppose  that  he  examines  a  wine-glass  of  water, 
boiling  hot,  and  a  gallon  of  tepid  water  by  a  thermometer,  he  will  find 
that  that  instrument  will  stand  much  higher  in  the  wine-glass  than  in 
the  gallon.  But  if  he  proceeds  to  determine  how  much  ice  the  two  por- 
tions of  water  will"  respectively  melt,  he  will  find  that  the  greatest  effect 
is  produced  by  the  lukewarm  water.  We  say,  therefore,  that  though  the 
thermometer  has  indicated  the  intensity  of  the  heat  in  the  two  portions 
of  water  respectively,  that  is  to  say,  their  temperatures,  it  has  not  indi- 
cated tlie  quantity  present  in  each,  but  the  melting  of  the  ice  has  revealed 
the  fact  that  the  tepid  water,  by  reason  of  its  larger  proportion,  contains 
a  larger  quantity  of  heat. 

It  may  be  repeated,  therefore,  that  the  absolute  quantity  of  heat  an- 
nually furnished  to  any  locality  is  by  no  means  -indicated  by  the  maxi- 
mum height  to  which  the  thermometer  will  rise  in  the  summer  season, 
yet  it  is  upon  that  condition,  quantity,  that  the  tint  of  the  complexion 
depends. 

That  climate  does  thus  influence  color  is  clearly  demonstrated  by  the 
Quantity  of  ^act  ^at  a  fam^7  °f  men,  indisputably  derived  from  a  corn- 
heat  influences  mon  stock,  have  different  complexions  in  different  countries. 
The  Jews  of  the  north  of  Europe  are  fair  men,  often  having 
red  beards  and  blue  eyes.  As  we  trace  them  in  their  southeasterly  dis- 
tribution, their  color  deepens  by  degrees.  In  their  original  country  they 


INDO-EUROPEANS. 


573 


are  tawny,  still  farther  on  they  are  deep  brown,  and  in  Malabar  almost 
black.  A  more  interesting  and  more  general  instance  is  offered  by  tho 
race  to  which  we  belong,  the  Indo-European,  which  reaches,  in  one  un- 
broken column,  across  Western  Asia,  through  Europe,  from  Hindostan  to 
the  British  Islands.  That  this  is  one  homogeneous  family,  derived  from 
a  common  stock,  is  proved  beyond  all  possibility  of  a  doubt  by  the  affin- 
ities of  its  languages,  all  showing  a  relation  to  the  ancient  Sanscrit, 
and  even  betraying,  by  their  varied  designations  of  certain  objects,  in  an 
approximate  manner,  the  time  at  which  the  progress  of  this  column  was 
made — that  it  was  anterior  to  the  introduction  of  the  metals,  in  the  age 
of  stone,  as  some  authors  have  designated  it,  when  weapons  and  imple- 
ments of  that  material  alone  were  employed,  for  the  names  of  the  metals 
are  different  in  many  of  the  different  languages  of  this  race. 

But  how  is  it  as  regards  the  complexion  of  the  Indo-European s  ?  To 
the  northwest  it  is  light,  but  it  darkens  toward  the  extreme  Variations  im- 
southeast  in  India,  the  distribution  in  this  respect  having 
been  doubtless  much  better  marked  in  former  times,  before  race, 
it  was  disturbed  by  the  influences  of  civilization.  Thus  the  Eoman  au- 
thors speak  of  the  northern  Germans,  of  the  Britons,  and  the  Gauls,  as 
being  red-haired,  blue-eyed,  and  very  light  in  their  complexion.  It  is 
riot  to  be  understood,  however,  that  the  tint  deepens  through  various 
shades  of  olive  and  brown  by  a  steady  progress  as  we  pass  toward  India, 
for  the  physical  principles  on  which  we  have  been  dwelling  would  pre- 
pare us  to  expect  that,  whenever  we  reach  regions  more  elevated  above 

the  level  of  the  sea,  the  com- 
plexion of  the  natives  will  be 
lighter.     For  this  reason,  the 
inhabitants  of  the  range  of  the 
Caucasus,  and  again  those  of 
the  great  elevations  of  the  Him- 
malaya  Mountains  and  sour- 
ces of  the  Ganges,  are  as  light 
a     as   the   southern  Europeans, 
H|  and  there  very  frequently  is 
jji    seen  the  auburn-bearded,  and 
blue  or  gray  eyed  man. 

While  the  complexion  thus 
depends  on  the  heat,  the  form 
of  the  skull  is  determined  by 
the  condition  of  development 
of  the  brain,  and  this  is  the 
more  perfect  where  life  is  main- 
Brahmin,  tained  in  circumstances  of 


Fig.  269. 


574 


MONGOLS. 


plenty,  indolence,  luxury,  ease.  In  Hindostan,  among  the  natives  of 
high  caste,  have  from  time  to  time  arisen  men  whose  mental  endowments  • 
have  been  in  no  respect  inferior  to  those  of  Europeans — statesmen,  poets, 
soldiers,  astronomers,  mathematicians.  Complexion  apart,  the  portrait 
of  Ram  Ruttum,  a  Brahmin,  Fig.  269,  taken  Iby  Mr.  Branwhite,  presents 
an  intelligent  and  agreeable  countenance,  though,  perhaps,  with  an  air  of 
effeminacy. 

Let  us  examine  a  second  of  our  subdivisions,  the  Mongol,  character- 
ized as  descending;  from  a  common  stock  by  the  affinities  of 

Variations  im-    f  °  .... 

pressed  on  the  its  languages,  though  having  a  geographical  distribution  from 
Mongol  race.  the  Indian  Qcean  to  tlie  tfioKs  of  the  Polar  Sea.  As  with 
the  Indo-European  race,  so  with  this,  the  color  becomes  darker  as  the 
tropic  is  approached — so  dark,  indeed,  that,  in  the  lowest  latitudes  to 
which  its  nations  reach,  they  may  be  said  to  be  black.  From  this  they 
pass  through  various  shades  of  brown  and  olive  as  a  progress  to  the 
higher  latitudes  is  made,  the  pale  countenance  reappearing  in  North  Tar- 
tary,  and  attaining  to  whiteness  in  the  fish-feeding  tribes,  Samoiedes,  on 
the  shores  of  the  Icy  Sea.  But  here,  again,  the  complexion  and  the  lati- 
tude are  not  in  correspondence :  on  the  low  shores  of  China  the  natives  are 
tawny,  but  in  the  mountainous  regions  of  the  northwest  of  that  country 
there  are  tribes  spoken  of  by  those  who  have  seen  them  as  of  surprising 
whiteness,  and  a  similar  circumstance  occurs  among  the  Tartar  tribes  of 
the  very  elevated  plateaux  of  Central  Asia. 

Although  the  Chinese  countenance,  both  of  the  indigenous  race  and  the 

dominant  Tartars,  is  very  characteris- 
tic, as  seen  in  the  annexed  portrait, 
Fig.  270,  from  Dr.  Prichard,  the  form 
of  the  skull  expresses  a  high  intellec- 
tual culture,  of  which  also  their  civil- 
ization and  their  polity  are  a  surpris- 
ing proof.  The  difficulties  of  govern- 
ing masses  of  men  concentrated  in  a 
narrow  space  seem,  by  the  statesmen 
of  that  nation,  to  have  been  in  a  great 
measure  overcome.  On  the  Chinese 
rivers  there  are  many  great  cities,  vast- 
ly outnumbering  in  their  population 
the  largest  European  capitals.  Under 
the  government  of  the  emperor,  it  is  said  that  there  live,  in  security  and 
repose,  one  third  of  the  human  race!  Such  a  spectacle  may  impress 
even  the  philosopher  with  sentiments  of  respect  and  admiration. 

The  hardships  of  life  have  left  their  impression  on  the  form  of  the  skull 
of  the  North  Asiatic,  whose  energies  have  to  be  directed  to  the  support  of 


Fig.  270. 


Chinese. 


AMERICAN   INDIANS. 


575 


Fig.  271. 


animal  existence.  The  portrait 
of  a  Kamtschatdale,  Fig.  271, 
selected  by  Dr.  Prichard  as  an 
example,  shows  the  projecting 
muzzle,  that  invariable  index  of 
want,  and  true  animal  feature. 
The  complexion  is  nevertheless 
in  correspondence  with  the  low 
temperature  of  the  country. 
A  like  examination  of  a  third 

of  the  subdivisions   Variations  im- 


Kamtschatdale. 


Fig.  272. 


Can,  equally  Well  il-    dian  race. 

lustrates  the  influence  of  heat. 
These,  though  popularly  spoken 
of  as  red,  and  often  regarded  as  presenting  the  same  color  from  the  North 
Polar  Sea  to  Terra  del  Fuego,  are  very  far  from  offering  such  a  uniform- 
ity. The  Esquimaux  on  the  north,  and  the  Fuegians  on  the  south,  are 
light,  the  tint  of  the  native  races  deepening,  to  a  certain  degree,  as  the 
equator  is  approached  —  a  gradual  deepening,  much  better  marked  in 
South  than  in  North  America,  and  on  the  Pacific  than  on  the  Atlantic 

slope.  As  examples  of  the 
North  American  Indians, 
we  may  take  the  portraits, 
by  Mr.  Catlin,  of  Black 
Hawk,  Fig.  272,  and  Tuch- 
te,Fig.  273,  page  576;  the 
former  a  Sac,  the  latter  a 
Cherokee.  It  is  sufficient 
to  compare  the  counte- 
nances of  these  Indians 
with  those  of  California,  as 
figured  in  the  Voyage  Pit- 
toresque  of  Choris,  Fig. 
274,  page  576,  to  realize 
how  erroneous  is  the  preva- 
lent statement  that  all  the 
American  tribes,  both  of 
the  north  and  south  conti- 
tinent,  are  alike.  The  ol- 
ive-black Indians  of  the  Pacific  slope,  though  their  lips  are  thick  and 
their  noses  flat,  have  lank  and  not  woolly  hair,  Fig.  275,  page  576.  On 
the  Atlantic  shore,  as  is  well  known,  the  temperature,  in  passing  to  lower 


^^^) 


American  Indian. 


576 


AMEKICAN   INDIANS. 


Fig.  27C 


latitudes,  docs  not  so  rapidly  vary ; 
and  on  the  Pacific  the  mean  heat  is* 
much  higher  than  on  the  Atlantic 

Fig.  274. 


American  Indian. 

for  the  same  parallel  of  latitude. 


Calrornla  Indian. 


Fig.  2T5. 


California  Indians. 


In  South  America,  the  so-called  red  race,  as  we  have  just  observed,  is 
deeper  in  complexion  as  we  pass  from  Terra  del  Fuego  and  Patagonia 
northward  toward  the  line.  The  Chilians  are  darker  than  the  Fuegians, 
and  the  Peruvians  darker  than  the  Chilians.  As  the  topographical  con- 
struction of  that  continent  would  lead  us  to  infer,  there  is  an  analogous 
distribution  from  west  to  east,  crossing  the  preceding  at  right  angles ; 
the  Inca  race,  who  inhabit  the  plateaux  of  the  Andes,  are  lighter  than 


AFRICANS. 


577 


corresponds  to  the  latitude ;  but  from  this  point,  passing  to  the  east,  the 
-Brazilio-Guarani  are  darker  as  we  approach  the  Atlantic  Ocean.  It  may 
with  truth  be  said  that  the  intervention  of  the  Gulf  of  Mexico  and  Ca- 
ribbean Sea  has  lightened  the  complexion  of  the  aboriginal  tribes  of 
North  and  South  America. 

In  the  last  place,  we  may  consider,  in  like  manner,  the  African  races. 
These  are,  as  we  should  expect  from  the  high  temperature  y  .  . 
of  that  continent,  all  dark,  yet  not  equally  so,  for  the  Berbers  pressed  on  the 
toward  the  Mediterranean  shore,  and  the  Hottentots  and  Kaf-  African  races* 
firs  adjacent  to  the  Cape  of  Good  Hope,  are  of  a  lighter  hue.  In  this 
class  we  ought  also  to  enumerate,  as  an  example  of  no  common  interest, 
the  native  Egyptians,  who  are,  perhaps,  the  lightest  of  all.  It  does  not 
appear  that  there  has  been  any  marked  change  in  the  complexion  of  the 
aboriginal  Egyptian  for  the  last  three  thousand  years,  so  far  as  can  be 
judged  from  a  comparison  of  the  descriptions  and  paintings  which  have 
descended  to  our  times,  with  the  existing  Copts.  Leaving  the  Mediter- 
ranean shore,  and  advancing  to  the  south,  we  pass  through  bands  of  pop- 
ulation sensibly  becoming  darker,  save  where  a  disturbance  arises  by  rea- 
son of  the  elevation  of  the  mountain  ranges.  On  the  north  of  the  equa- 
tor the  negro  land  is  not  reached  until  we  are  within  10°  lati-  The  negro 
tude.  The  true  negro  occupies  a  zone  crossing  through  the  con-  zone- 
tinent  west  and  east.  If  our  examination  be  made  meridionally,  in  the 
manner  just  supposed,  but  along  the  Eed  Sea  coast,  the  complexion  of 
the  inhabitants  is  observed  to  darken  through  Upper  Egypt  and  in  Abys- 
synia.  Of  this  country  it  is  interesting  to  remark  that  it  still  retains  the 
Christian  faith  as  delivered  to  it  in  the  remotest  times  of  the  Church. 

The  portrait  of  an  Abyssinian, 
Fig.  276,  from  M.  d'Abbadie,  shows 

Fig.  276. 


Abyssinian.  Native  of  Madagascar. 

an  admixture  of  the  Arab  lineaments,  though  there  is  no  reason  to  suppose 

Go 


578 


AFRICANS. 


that  this  is  due  to  the  admixture  of  Arab  blood.  Of  the  two  classes 
of  Abyssinians,  those  who  inhabit  the  more  southerly  parts  have  a  coun- 
tenance much  more  approaching  to  the  negro.  They  are,  indeed,  an  in- 
trusive race,  who  conquered  in  more  recent  times  the  regions  in  which 
they  are  settled.  It  is  said  that  the  Amharic,  the  language  of  the  true 
Abyssinians,  is  singularly  analogous  to  the  Hebrew. 

As  resembling  the  Abyssinians  in  many  respects,  though  on  the  op- 
posite side  of  the  equator,  may  be  mentioned  the  natives  of  Madagascar, 
Fig.  277,  p.  577.  Presenting,  in  some  particulars,  the  traces  of  Arab  in- 
fluence, it  has  nevertheless  been  inferred,  partly  from  their  language  and 
partly  from  their  features,  that  the  most  numerous  class  is  of  Malay  ori- 
gin. Though  among  the  inferior  tribes  there  are  some  which  are  black, 
the  complexion  of  this  is  olive,  and  the  hair  is  not  woolly,  though  it 
curls. 

It  should  be  constantly  borne  in  mind  that  the  resemblance  of  features 
Evidences  from  is  no  proof  of  a  community  of  origin.  The  influence  of  cli- 
countTnance  mate  and  of  manner  of  life  is  so  great  that  in  a  due  period 
and  language,  of  time  the  most  diverse  tribes  will  show  similar  lineaments. 
Analogy  in  the  structure  of  languages  and  identity  in  vocabulary  is 
much  better  evidence,  though  even  this  must  be  received  with  caution.  In 
reference  to  this,  it  has  been  very  significantly  remarked  that  birds  of  the 
Fig.  2T8.  same  kind  sing  the  same  notes 

in  all  countries,  even  though 
under  such  circumstances  as  to 
exclude  the  possibility  of  their 
having  been  taught  by  their 
parents. 

The  annexed  figure,  278,  is 
given  by  Dr.  Prichard  as  a 
specimen  of  the  natives  of  Mo- 
zambique. The  expression  is 
undoubtedly  much  superior  to 
that  prevailing  on  the  West  ' 
African  coast.  Of  some  of 
these  tribes  it  is  said  that  the 
Native  of  Mozambique.  hair  is  not  woolly,  but  merely 

frizzled.     It  grows  long,  and  hangs  in  slender  curls. 

Examining  the  zone  designated  as  negro  land,  we  find  that  the  negro 
Amelioration  character  of  its  inhabitants  is  not  in  all  parts  developed  with 
typeto^he0  equal  intensity.  The  maximum  is  shown  in  the  Guinea 
east.  countries,  and  from  thence  across  the  continent  to  the  east 

the  physiognomy  improves.  The  negro  characteristics  may  be  specified 
as  intense  blackness  of  the  skin,  woolly  hair,  thick  lips,  gaping  nostrils, 


THE  NEGRO. 


579 


Fig.  279. 


Negro  of  Guinea. 


Fig.  280. 


and  a  prognathous  skull.  But  the  negro 
aspect  is  not  limited  to  the  African  con- 
tinent ;  it  is  prolonged  or  projected  through 
the  Indian  into  the  Pacific  Ocean,  north 
and  south  of  the  equator,  in  a  zone  of 'many- 
degrees.  Sumatra,  Borneo,  Celebes,  New 
Guinea,  and  part  of  Australia,  lie  in  this 
zone.  In  these  various  countries,  one  or 
another  of  the  characteristics  we  have  men- 
tioned predominate,  in  part  through  the  in- 
fluence of  climate,  and  in  part  through  ad- 
mixture of  blood.  In  some  of  these  people 
the  hair  is  not  woolly ;  in  some,  the  lips 
are  thin,  and  the  nose  projecting ;  in  some, 
the  form  of  the  skull  indicates  a  great  su- 
periority over  the  West  African  tribes.  But,  whatever  these  modifica- 
tions may  be,  the  black  races  of  the  Pacific  present  in  their  general  ap- 
pearance so  predominating  a  negro  as- 
pect that  they  have  by  all  travelers 
been  classed  with  that  tribe.  Of  one 
of  these  nations,  Dampier,  the  early 
navigator,  speaks  as  "  shock,  curl-pa- 
ted,  New  Guinea  negroes. "  The  por- 
trait, Fig.  280,  from  Choris's  Voyage 
Pittoresque,  of  a  girl  of  the  island  of 
Luzon,  one  of  the  Philippines,  may  il- 
lustrate this  remark ;  for,  though  the 
form  of  the  head  shows  a  very  great 
advance  upon  that  of  the  Guinea  ne- 
gro, the  facial  angle,  respecting  which 
more  will  shortly  be  said,  being  much 
larger,  and  the  relative  size  of  the 
brain  therefore  increased,  the  counte- 
nance is  essentially  that  of  tropical 
Africa. 

The  projection  of  the  African  type  into  the  Pacific  is  crossed  at  a  cer- 
tain point  by  a  like  projection  of  the  dark  Asiatic  type,  and  yariations  im 
in  the  region  of  this  intersection  or  commingling  we  find  the  pressed  on  the 
most  degraded  specimens  of  humanity.  Pacific  race' 

From  these  regions,  as  we  pass  eastwardly  toward  the  American  con- 
tinent, the  improvement  becomes  very  striking;  thus  tne  Amelioration  of 
natives  of  the  Society  Islands,  though  living  within  the  the  Pelagian 
tropic,  are  of  a  clear  olive  or  brunette.     In  the  opinion  of  type  to  the  east> 


Philippine  negro. 


580  COMPARISON  OF  THE  SKELETON. 

some,  if  it  were  not  for  a  slight  thickness  of  the  lips  and  spreading  of 
the  nostrils,  the  countenance  would  be  European.  The  men  are  de- 
scribed as  "tall,  strong,  well-limbed,  and  finely  shaped."  Many  of  the 
children  have  flaxen  hair ;  and  sailors,  who  are  generally  competent 
judges  of  such  matters,  universally  yield  a  tribute  of  admiration  to  the 
prettiness  of  the  women.  Captain  Bligh  attributed  the  mutiny  in  his 
ship  to  that  interesting  cause. 

We  may  next  consider  variations  in  the  form  of  the  skeleton. 

Here,  more  particularly  in  the  classification  of  the  forms  of  skulls,  I 
Comparison  adopt  the  division  introduced  by  Dr.  Prichard,  from  whose 
of  skeletons,  work,  above  alluded  to,  the  following  passages  are  extracted : 

"  In  all  other  races,  compared  with  Europeans,  the  limbs  are  more 
crooked  and  badly  formed.     In  the  negro  the  bones  of  the  leg  are 
eg'  bent  outward.     Soemmering  and  Lawrence  have  observed  that 
the  tibia  and  fibula  in  the  negro  are  more  convex  in  front  than  in  Eu- 
ropeans ;  the  calves  of  the  legs  are  very  high,  so  as  to  encroach  upon  the 
hams  ;  the  feet  and  hands,  but  particularly  the  former^  are  flat ;  the  os 
calcis,  instead  of  being  arched,  is  continued  nearly  in  a  straight  line  with 
the  other  bones  of  the  foot,  which  is  remarkably  broad." 

"  It  was  observed  by  White,  and  has  been  generally  believed,  that 
the  length  of  the  forearm  is  so  much  greater  in  the  negro  than 

The  arm.    .  & 

in  the  European  as  to  constitute  a  real  approximation  to  the 
character  of  the  ape.  Facts,  however,  prove  but  a  very  slight  difference, 
and  by  no  means  greater  than  the  varieties  which  are  every  day  to  be 
observed  on  comparing  many  individuals  of  any  race  or  nation.  On  the 
other  hand,  the  difference  between  adult  apes  and  men  in  the  length  of 
the  extremities  is  so  great  as  to  render  all  such  comparisons  very  remote, 
and  of  very  doubtful  importance  with  respect  to  any  ulterior  conclusion. 
According  to  Mr.  Owen,  the  arms  of  the  orang  reach  to  the  heel,  or  at 
least  to  the  ankle-joint,  while  in  the  chimpanzee,  or  troglodyte,  they  ex- 
tend below  the  knee-joint.  This  is  a  most  decided  and  widely-marked  dif- 
ference between  the  most  anthropoid  apes  and  the  uncultivated  races  of 
men.  Yet  even  the  slightest  approach  to  the  former  shape  would  be  a 
curious  circumstance ;  if  it  could  be  fully  established,  it  would  tend,  with 
other  facts,  to  imply  that  the  savage  races  of  mankind  have  somewhat 
more  of  the  animal,  even  in  their  physical  conformation,  than  the  more 
cultivated  races,  or  those  whose  improvement  by  civilization  may  be 
dated  from  a  very  remote  era  in  the  history  of  the  world." 

"It  has  been  a  general  opinion,  since  the  time  pf  Soemmering,  that 

The  foramen     *^e  head  of  the  negro  is  placed  so  much  farther  backward  on 

magnum  of  the  the  vertebral  column  as  to  occasion  a  material  difference  in 

the  figure  of  the  whole  body.     It  was  observed  by  Dauben- 

ton  that  the  foramen  magnum  is  placed  in  quadrupeds  behind  the  centre 


FOUR   METHODS   OF   EXAMINING   THE    SKULL. 


581 


Fig.  281 


of  gravity,  whence  an  important  difference  arises  in  the  relative  position 
of  the  head  and  trunk  in  man  and  in  inferior  animals.  The  extent  of 
this  difference,  when  the  human  skeleton  is  compared  with  that  of  the 
simias,  has  been  most  fully  made  known  by  Mr.  Owen,  who  has  shown 
that  it  is  much  greater  in  respect  to  the  adult  ape  than  it  has  hitherto 
been  supposed.  But  there  is,  in  reality,  no  difference  in  human  races. 
The  foramen  magnum  is  only  posterior  in  the  negro  skull  to  its  place 
in  the  European,  in  consequence  of  the  projection  of  the  upper  jaw,  par- 
ticularly of  the  alveolar  process." 

In  illustration  of  the  statement  of  Mr.  Owen  respecting  the  relative 

length  of  the  arm  in  man 
and  in  the  more  anthropoid 
apes,  I  give  the  annexed 
photograph,  Fig.  281,  of 
the  human  skeleton  and 
those  of  the  chimpanzee 
and  orang.  Of  the  chim- 
panzee it  should  be  ob- 
served that  the  specimen 
was  young.  They  are  all 
brought  nearly  to  the  same 
size  by  adjusting  the  dis- 
tances at  which  they  were 
taken.  The  human  skele- 

Skeleton  of  man,  chimpanzee,  and  orang.  fOU  Was  that  of  a  man  more 

than  six  feet  in  height. 

There  are  four  different  views  from  which  an  examination  ^ 

K  our  modes  of 

of  the  skull  of  man  and  animals  may  be  made :  1st.  The  lat-  examining  the 
eral ;  2d.  The  vertical ;  3d.  The  basilar ;  4th.  The  front.  skulL 

1st.  The  lateral  view,  or  Camper's  method,  is  thus  described  by  the 
anatomist  who  introduced,  it,  and  whose  name  it  bears. 

"The  basis  on  which  a  distinction  of  nations  is  founded  may  be  dis- 
played by  two  straight  lines,  one  of  which  is  to  be  drawn  The  lateral 
through  the  meatus  auditorius  to  the  base  of  the  nose,  and  view,  or  Cam- 
the  other  touching  the  prominent  centre  of  the  forehead,  and  per  s  n 
falling  thence  on  the  most  advancing  part  of  the  upper  jaw-bone,  the 
head  being  viewed  in  profile.  In  the  angle  produced  by  these  two  lines 
may  be  said  to  consist  not  only  the  distinctions  between  the  skulls  of 
the  several  species  of  animals,  but  also  those  which  are  found  to  exist 
between  different  nations ;  and  it  might  be  concluded  that  Nature  has 
availed  herself,  at  the  same  time,  of  this  angle  to  mark  out  the  diversi- 
ties of  the  animal  kingdom,  and  to  establish  a  sort  of  scale  from  the  in- 
ferior tribes  up  to  the  most  beautiful  forms  which  are  found  in  the  human 


582 


THE   LATERAL   VIEW,  OR   CAMPER'S   METHOD. 


species.  Thus  it  will  be  found  that  the  heads  of  birds  display  the  small- 
est angle,  and  that  it  always  becomes  of  greater  extent  in  proportion  as 
the  animal  approaches  more  nearly  the  human  figure.  Thus  there  is 
one  species  of  the  ape  tribe  in  which  the  head  has  a  facial  angle  of  forty- 
two  degrees ;  in  another,  of  the  same  family,  which  is  one  of  those  simige 
most  approximating  in  figure  to  mankind,  the  facial  angle  contains  ex- 
actly fifty  degrees.  Next  to  this  is  the  head  of  the  African  negro,  which, 
as  well  as  that  of  the  Kalmuck,  forms  an  angle  of  seventy  degrees,  while 
the  angle  discovered  in  the  heads  of  Europeans  contains  eighty  degrees. 
On  this  difference  of  ten  degrees  in  the  facial  angle  the  superior  beauty 
of  the  European  depends  ;  while  that  character  of  sublime  beauty,  which 
is  so  striking  in  some  works  of  ancient  statuary,  as  in  the  head  of  Apollo 
and  in  the  Medusa  of  Sisocles,  is  given  by  an  angle  which  amounts  to 
one  hundred  degrees." 

As  illustrations  of  this  view,  the  subjoined  profiles  of  the  skull  of  the 
European,  Fig.  282,  the  negro,  Fig.  283,  the  chimpanzee,  Fig.  284,  and 

Fig.  282.  Fig.  283. 


European. 

the  orang,  Fig.  285,  are  given. 

Fig.  284 


Negro. 

Of  the  latter,  which,  of  apes,  are  among 

Fig.  285. 


Chimpanzee. 


those  most  closely  approaching  to  man, 
the  chimpanzee  is  a  native  of  tropical 
Africa,  and  the  orang  of  the  Indian 
Archipelago. 

2d.  The  vertical  view,  or  Blumenbach's  method, 


Orang, 


THE   VERTICAL   VIEW,  OR   BLUMENBACIl'S   METHOD.  583 

"  Blumenbacli  gives  the  following  account  of  the  way  of  describing 
heads,  which,  he  says,  is  the  result  of  his  own  observations  The  vertical 
in  a  long  and  constant  study  of  his  collections  of  the  skulls  menb^ch? 1U' 
of  different  nations :  He  remarks  that  the  comparison  of  the  method, 
breadth  of  the  head,  particularly  of  the  vertex,  points  out  the  principal 
and  most  strongly-marked  differences  in  the  general  configuration  of  the 
cranium.  He  adds  that  the  whole  cranium  is  susceptible  of  so  many  va- 
rieties in  its  form,  the  parts  which  contribute  more  or  less  to  determine 
the  national  character  displaying  such  different  proportions  and  direc- 
tions, that  it  is 'impossible  t6  subject  all  these  diversities  to  the  measure- 
ment of  any  lines  or  angles.  In  comparing  and  arranging  skulls  accord- 
ing to  the  varieties  in  their  shape,  it  is  preferable  to  survey  them  in  that 
method  which  presents  at  one  view  the  greatest  number  of  characteristic 
peculiarities.  t  The  best  way  of  obtaining  this  end  is  to  place  a  series 
of  skulls  with  the  cheek-bones  on  the  same  horizontal  line,  resting  on  the 
lower  jaws,  and  then,  viewing  them  from  behind,  and  fixing  the  eye  on 
the  vertex  of  each,  to  mark  all  the  varieties  in  the  shape  of  parts  that 
contribute  most  to  the  national  character,  whether  they  consist  in  the  di- 
rection of  the  maxillary -and  malar  bones,  in  the  breadth  or  narrowness 
of  the  oval  figure  presented  by  the  vertex,  or  in  the  flattened  or  vaulted 
form  of  the  frontal  bone.' " 

By  this  means  of  comparison  Blumenbach  obtains  a  division  of  skulls 
into  three  classes,  the  Caucasian,  Mongol,  and  Negro.  They  are  repre- 
sented in  Fig.  286,  Fig.  287,  Fig.  288,  and  Dr.  Prichard  has  added  to 
these  figures  Fig.  289,  the  artificially  elongated  skull  of  an  ancient  Pe- 
ruvian, from  the  burial-places  of  Titicaca. 

Fig.  286.  p-ig,  287. 


3.  The  basilar  view,  or  Owen's  method. 

"  No  single  view  of  the  skull  determines  so  much  in  regard  to  its  gen- 
eral configuration  as  that  of  the  basis.  *  The  importance  of  The  basilar 
this  manner  of  examining  the  bony  structure  of  the  head  view,  or  Owen's 
has  been  demonstrated  in  the  fullest  manner  by  Mr.  Owen, 


584  THE   BASILAE,  OR   OWENS   METHOD. 

Fig.  2SS.  Fig.  289. 


Negro. 

in  his  excellent  memoir  on  the  struc- 
ture of  the   orang  and  chimpanzee. 

The  relative  proportions  and  extent,  and  the  peculiarities  of  formation 
of  the  different  parts  of  the  cranium,  are  more  fully  discovered  by  this 
mode  of  comparison,  which  has  hitherto  been  much  neglected,  than  by 
any  other  method." 

Fig-  200.  mn  291< 


Skull  of  orang. 


Human  skull. 

"  It  may  be  observed,  in  this  view  of  the  cranium,  that  the  antero- 
posterior  diameter  of  the  basis  of  the  skull  is  in  the  orang  very  much 
larger  than  in  man.  The  most  striking  circumstance  which  displays 
this  difference  is  the  situation  occupied  by  the  zygomatic  arch  in  the 
plane  of  the  basis  of  the  skull.  In  all  races  of  men,  and  even  in  human 
idiots,  the  entire  zygoma  is  included  in  the  anterior  half  of  the  basis  cra- 
nii ;  in  the  head  of  the  adult  troglodyte,  or  chimpanzee,  as  well  as  in  that 
of  the  satyr,  or  orang,  the  zygoma  is  situated  in  the  middle  region  of  the 
skull,  and  in  the  basis  occupies  just  one  third  part  of  the  entire  length 
of  its  diameter.  Posterior  to  the  zygomata,  the  petrous  portions  have, 
in  the  simian,  a  larger  development  in  the  antero-posterior  direction. 


THE  FEONT  VIEW,  OE  PEICHAED'S   METHOD.  585 

Another  most  remarkable  character,  in  respect  to  which  those  anatomists 
have  been  greatly  deceived  who  compared  only  young  troglodytes  with 
man,  is  the  great  occipital  foramen,  a  feature  most  important  as  to  the 
general  character  of  structure  and  to  the  habits  of  the  whole  being. 
This  foramen,  in  the  human  head,  is  very  near  the  middle  of  the  basis 
of  the  skull,  or,  rather,  it  is  situated  immediately  behind  the  middle 
transverse  diameter,  while  in  the  adult  chimpanzee  it  is  placed  in  the 
middle  of  the  posterior  third  of  the  basis  cranii.  A  third  characteristic 
in  the  ape  is  the  greater  size  and  development  of  the  bony  palate,  in  con- 
sequence of  which  the  teeth  are  much  larger  and  more  spread,  and  want 
that  continuity  which  is,  generally  speaking,  a  characteristic  of  man;  and 
intervals  between  the  laniary,  cutting,  and  bicuspid  teeth  admit,  as  in 
the  lower  tribes  of  animals,  the  apices  of  teeth  belonging  to  the  opposite 
jaws.  Fourthly,  the  basis  of  the  skull  is  flat,  owing  to  the  want  of  that 
'downward  development  of  the  brain,  and  of  the  bony  case  connected  with 
the  greater  dimension  which  the  cerebral  organ  acquires  in  the  human 
being  compared  with  the  lower  tribes." 
4.  The  front  view,  or  Prichard's  method. 

"Neither  the  facial  angle  of  Camper,  nor  the  method  of  viewing  the 
skull  proposed  by  Blumenbach,  affords  a  satisfactory  display  T^efrontview 
of  the  characteristics  of  the  pyramidal  or  lozenge-faced  skull."  or  Prichard's 
.  292,  which  is  the  drawing  of  the  skull  of  an  method' 
Fig,  292.  Esquimaux,  the  lines  drawn  from  the 

zygomatic  arch,  touching  the  temples, 
meeting  over  the  forehead,  form  with 
the  basis  a  triangular  figure.  *  These 
two  lines  in  well -formed  European 
heads  are  parallel,  the  forehead  being 
very  much  broader  than  in  the  heads 
of  Esquimaux,  and  other  races  whose 
skulls  belong  to  the  same  great  division 
of  human  crania,  among  whom  are  the 
Mongolians,  and  other  nomadic  nations 
of  Northern  Asia.  The  most  striking 
characteristic  of  these  skulls  is  the  great 
Esquimaux.  lateral  or  outward  projection  of  the  zyg- 

omatic arch.  The  cheek-bones,  rising  from  under  the  middle  of  the  or- 
bit, do  not  project  forward  and  downward  under  the  eyes,  as  in  the  prog- 
nathous skull  of  the  negro,  but  take  a  direction  laterally  or  outward,  and 
turn  backward  to  meet  a  corresponding  projection  of  the  process  of  the 
temporal  bone,  and  form  with  it  a  large,  rounded  sweep  or  segment  of  a 
circle.  The  orbits  are  large  and  deep.  The  upper  part  of  the  face  being 
remarkably  plane  or  flat,  the  nose  flat,  and  the  nasal  bones,  as  well  as  the 


586  CLASSIFICATION    OF   SKULLS. 

space  between  the  eyebrows,  nearly  on  the  same  plane  with  the  cheek- 
bones, the  triangular  space  described  by  the  lines  (drawn  on  the  wood- 
cut) may  be  compared  to  one  of  the  faces  of  a  pyramid.  The  whole  face, 
instead  of  an  oval  form,  as  in  most  Europeans  and  many  Africans,  is  of 
a  lozenge  shape." 

"  Another  characteristic  in  most  of  the  pyramidal  skulls,  or,  rather,  in 
the  form  of  the  face  to  which  this  configuration  of  the  skull  gives  rise, 
is  the  apparently  angular  position  of  the  aperture  of  the  eyelids.  There 
is  no  want  of  parallelism  in  the  orbits,  or,  rather,  of  coincidence  in  the 
transverse  sections  of  the  orbital  cavities.  The  obliquity  consists  in 
the  structure  of  the  lids  themselves ;  the  skin,  being  tightly  drawn  over 
the  large  protuberance  of  the  malar  bone,  under  the  outer  angle  of  the 
eye,  and  at  the  inner  extremity  smoothly  extended  over  the  lower  nasal 
bones,  while  the  bridge  of  the  nose  is  scarcely  elevated  above  the  plane 
of  the  suborbital  spaces,  gives  to  the  eye  the  appearance  of  being  placed 
with  the  inner  angle  downward." 

"  The  oval  or  elliptical  form  is  that  of  Europeans,  and  the  southern 
Asiatics  who  resemble  them  ;  the  zygomatic  bones  and  the  jaws  being 
less  protuberant,  the  entire  outline  of  the  head,  viewed  from  above,  has 
no  projecting  angular  parts,  and  is  defined  by  an  oval  circumference.  But 
in  that  oval  figure,  or  rather  ellipse,  the  two  diameters  vary  considera- 
bly in  proportion ;  in  other  words,  some  nations  have  rounder,  others  more 
elongated  heads.  The  shape  of  the  brain,  and  of  the  skull  at  its  basis, 
is  in  the  rounder  heads  more  like  that  of  the  pyramidal  skull,  or  the 
cranium  of  the  northern  Asiatics ;  in  the  narrower  heads  it  approaches 
the  figure  of  the  elongated,  or  negro  head." 

We  may  therefore  conveniently  classify  skulls  in  three  divisions : 

1st.  The  prognathous,  which  is  represented  in  Fig.  293,  being  the 
Classification  skull  Of  a  negro  of  very  forbidding  aspect.  This  form  is 
of  skulls.  marked  by  a  forward  projection  of  the  jaws,  the  brain  being 
therefore,  as  it  were,  thrown  backward  as  respects  the  face,  the  forehead 
being  more  horizontal  and  low. 

2d.  The  pyramidal,  Fig.  292,  which  gives  rise,  as  has  been  stated 
above,  to  the  lozenge-shaped  face. 

3d.  The  elliptical  or  oval,  which,  viewed  from  above,  has  an  oval  con- 
tour without  projecting  parts,  and  in  the  profile  shows  a  large  facial  an- 
gle, as  in  the  French  skull,  Fig.  294. 

These  forms  of  skull  seem  to  be  connected  very  closely  with  habits 
Connection  of  of  life :  the  prognathous  with  the  savage  state,  or  that  of 
the  skuTand  ^untmg  >  the  pyramidal  with  a  wandering  pastoral  life  ;  and 
manner  of  life,  the  elliptical  with  that  of  civilization. 

With  respect  to  the  form  of  the  pelvis  in  different  nations,  the  varia- 
tions are  by  no  means  so  significant  as  in  the  case  of  the  cranium,  inas- 


EFFECTS   OF  WANT  AND   DEGRADATION. 

Fig.  293.  Fig.  294. 


587 


Negro. 


French. 


much  as  they  are  of  indiscriminate  oc- 
currence.    It  may  perhaps  be  maintained  in  a  general  way, 
that  in  the  less  advanced  tribes,  as  in  the  female  Hottentot, 
there  is  an  approximation  to  the  form  exhibited  by  the  simiae,  the  iliac 
bones  being  more  vertical,  and  the  whole  structure  characterized  by  its 
length  and  narrowness.     Professor  Weber,  who  has  examined  this  sub- 
ject with  care,  concludes  that  no  particular  figure  of  the  pelvis  is  a  char- 
acteristic of  any  one  race. 

The  remarks  which  have  been  made  respecting  variations  of  complex- 
ion, as  exhibited  in  different  climates,  might  almost  be  re-  The  physical 
peated  as  respects  variations  of  the  form  of  the  skull,  origi-  a^^inthe*1' 
nating  in  difference  of  physical  circumstances ;  for  as  the  skull, 
complexion  varies  in  different  temperatures,  so  does  the  figure  of  the 
skull  in  different  social  conditions.  The  elliptical  skull,  which  beyond 
all  doubt  is  that  which  belongs  to  man  in  his  most  civilized  state,  may 
be  deteriorated  and  degraded  even  to  the  lowest  prognathous  form. 
Want  and  squalid  misery  will  produce  this  result.  Igno-  its  degradation 
ranee,  mere  animal  life,  social  degradation,  lead  to  its  ap-  b7  want- 
proach  in  varied  degrees.  Even  in  the  large  European  cities  we  recog- 
nize the  incipient  stages  of  it  in  those  classes  who  follow  a  precarious 
life — the  projecting  jaw,  the  retreating  forehead,  the  mouth  habitually 
open,  or  the  lips  parted  so  as  to  show  the  teeth.  Mr.  Thackrah,  in  his 
work  on  the  Effects  of  Arts,  Trades,  etc.,  on  Health  and  Longevity,  says, 
"  I  stood  in  Oxford  Road,  Manchester,  and  observed  the  stream  of  oper- 
atives as  they  left  the  mills  at  twelve  o'clock.  The  children  were  almost 
universally  ill-looking,  small,  sickly,  barefoot,  and  ill-clad.  Many  ap- 
peared to  be  no  older  than  seven.  The  men,  generally  from  sixteen  to 
twenty-four,  and  none  aged,  were  almost  as  pallid  and  thin  as  the  chil- 
dren. The  women  were  the  most  respectable  in  appearance,  but  I  saw 
no  fresh,  fine-looking  individuals  among  them.  Here  I  saw,  or  thought 
I  saw,  a  degenerate  race — human  beings  stunted,  enfeebled,  depraved." 
Under  the  opposite  circumstances,  where  life  is  maintained  in  indolence 


588  PROGNATHOUS   AND   ELLIPTICAL   SKULLS. 

and  plenty,  the  converse  effects  may  take  place.  Of  this,  perhaps  the 
its  rectification  most  striking  illustration  is  that  pointed  out  by  Dr.  Prichard 
by  luxury.  of  the  loss  of  the  pyramidal  form  of  skull  by  the  European 
Turks,  a  form  which  appertained  to  their  Asiatic  ancestors,  and  the  as- 
sumption of  the  elliptical,  the  skull  not  of  a  wandering,  but  of  a  station- 
ary and  civilized  race.  Nor  has  this  transmutation  taken  place  in  them, 
in  the  short  period  since  they  made  their  European  conquest,  because  of 
the  influence  exercised  by  the  Circassian  and  Georgian  women  intro- 
duced into  their  harems,  for  this  has  been  upon  too  small  a  scale  to  pro- 
duce such  a  general  result,  and  is  a  luxury  which  can  only  be  indulged 
in  by  the  wealthier  classes. 

As  a  descent  is  made  to  the  skull  of  the  prognathous  form,  the  coun- 
Contrast  be-  tenance  loses  those  features  which  we  regard  as  being  beau- 
nltehoushand°et  tiful»  and  assumes  a  baser  cast.  When  it  has  reached  the 
liptical  skulls.  limit  in  that  direction,  it  is  actually  hideous,  recalling  at 
once  the  detestable  aspect  of  the  ape.  In  this  state,  in  the  tropical  cli- 
mates, the  lips  are  thick,  the  hair  woolly,  the  nostrils  gaping.  The  in- 
tellectual powers  are  correspondingly  depressed  ;  the  dullness  of  the  eye, 
its  porcelain-like  sclerotic  contrasting  with  the  blackness  of  the  skin,  is 
in  correspondence  with  the  low  and  degraded  mental  power.  On  the 
contrary,  when  the  passage  is  made  toward  the  elliptical  form,  the  coun- 
tenance becomes  more  beautiful  and  interesting,  capable  of  expressing  the 
most  refined  mental  emotions.  The  eyes,  in  an  indescribable  but  sig- 
nificant manner,  manifest  the  exalted  powers  of  the  mind,  and  the  lips 
are  composed  or  compressed. 

If  I  am  not  mistaken,  darkness  of  the  skin  and  a  prognathous  form  of 
Mode  in  which  skull  may  be  dependent  in  the  dark  tribes  on  the  same  cir- 
darkPcompCiex-  cumstance.  Functionally  the  liver  is  in  connection  with  the 
i°n.  calorifacient  apparatus,  its  secretion,  the  bile,  as  shown  in 

Chapter  XL,  coinciding  in  habitudes  with  a  hydrocarbon.  Much  of  it 
is  therefore  reabsorbed,  and  eventually  devoted  for  the  support  of  a  high 
temperature.  But,  besides  this  combustible  material,  the  bile  likewise 
contains  a  coloring  matter,  which  is  in  all  respects  an  effete  body,  and 
useless  to  the  system.  This  pigment  is  derived  from  the  blood-discs, 
or,  rather,  from  their  hasmatin,  as  is  proved  by  the  fact  that  it  occurs  in 
the  meconium  of  the  new-born  infant,  and  likewise,  like  hgematin,  it  is 
rich  in  iron.  Its  source  is,  therefore,  not  immediately  from  the  food. 
To  remove  this  useless  material  is  thus  one  of  the  primary  functions  of 
the  liver. 

Now  there  is  no  organ  which  is  more  quickly  disturbed  in  its  duty  by 
Influence  of  the  a  high  temperature  than  the  liver.  Whether  such  a  high 
the6  temperature  produces  its  effect  through  a  disturbance  of  the 


complexion.      action  of  the  lungs,  or  through  an  impression  on  the  skin,  is 


ORIGIN  OF  COLOR.  589 

quite  immaterial.  If  the  organ  be  in  any  manner  enfeebled  in  its  duty, 
and  no  other  avenue  is  open  through  which  the  degenerating  hasmatin 
may  escape,  it  must  accumulate  in  the  circulation,  and  be  deposited  here 
and  there  in  suitable  places.  Under  such  circumstances,  there  arises  a 
tendency  for  its  accumulation  in  a  temporary  manner  in  the  lower  and 
more  spherical  cells  of  the  cuticle,  from  which  it  is  removed  by  their 
gradual  exuviation  and  destruction  as  they  become  superficial.  The 
temporary  deposit  of  the  coloring  matter  in  tins  situation  imparts  to  the 
skin  a  shade  more  or  less  deep.  It  may  amount  to  a  perfect  blackness  ; 
for  the  origin  of  the  black  pigment  of  the  negro  is  the  same  as  The  color  of  the 
that  of  the  black  pigment  of  the  eye  in  all  races,  and  the  pre-  skin  derived 

,        .        .  t   •  L.  T    •    i       -.  from  the  h*- 

dominating  percentage  01  iron  it  presents  plainly  betrays  matin  of  the 
that  it  arises  from  a  degenerating  haimatin,  in  which  the  kiood. 
same  metal  abounds. 

I  believe,  therefore,  that  the  coloration  of  the  skin,  whatever  the  par- 
ticular tint  may  be,  tawny-yellow,  olive-red,  or  black,  is  connected  with 
the  manner  in  which  the  liver  is  discharging  its  function.  That  de- 
posits of  black  pigment  can  normally  arise  in  the  way  of  a  true  secretion 
by  cell  action  is  satisfactorily  proved  by  their  occurrence  in  angular  and 
ramified  patches  in  the  skin  of  such  animals  as  the  frog ;  and  that  hae- 
matin,  in  its  degeneration,  may  give  rise  to  many  different  tints,  is  sub- 
stantiated by  the  colors  exhibited  by  ecchymoses. 

It  is  not  to  be  forgotten  that  coloration  of  the  skin,  though  apparently 
persistent,  is  tending  continually  to  a  removal,  because  of  Constant  re- 
the  oxidation  which  is  taking  place  as  the  pigment  cells  ap-  ^^fof0^6 
proach  the  surface  of  the  cuticle  in  their  process  of  desquama-  skin, 
tion ;  but  as  this  goes  on,  new  cells  and  new  pigment  are  perpetually 
forming  beneath,  to  undergo  destruction  in  their  turn.  Under  this  point 
of  view,  the  complexion  of  the  skin  is  an  index  of  the  energy  with  which 
that  tissue  is  addressing  itself  for  the  removal  of  metamorphosing  ha3- 
matin.  In  accomplishing  this  removal,  the  liver,  in  the  fair  races  of  man- 
kind, exerts  a  sufficient  activity;  but  in  hot  climates,  the  habitation  of 
the  black  races,  either  through  a  diminished  power  of  that  gland,  or  be- 
cause of  an  increased  production  of  effete  pigment,  the  skin  has  to  lend 
its  aid,  and  the  degree  to  which  it  does  this  is  betrayed  by  the  depth  of 
its  hue. 

Having  thus  traced  the  coloration  of  the  skin  to  existing  peculiarities 
of  hepatic  action,  I  may  repeat  the  remark  already  made,  influence  of  the 
that  it  is  not  improbable  that,  in  the  most  degraded  negro  efon^he  form^f 
type,  the  prognathous  form  of  the  skull  may  be  attributed  the  skull. 
to  the  same  cause. 

Not  that  this  alone  is  always  the  cause,  for  a  prognathous  skull  can 
by  degrees  arise,  as  we  have  seen,  in  any  race,  even  the  white,  from  a 


590  EFFECT   OF   TEMPERATURE   ON   THE   SKULL. 

variety  of  causes,  such  as  misery,  want,  or  an  oppressed  social  state.  It 
is,  however,  on  all  hands  admitted  that  nothing  so  quickly  disturbs  the 
brain  in  its  action  as  functional  disturbance  of  the  liver.  If,  through  a 
partial  failure  in  the  operation  of  that  great  gland,  the  products  which  it 
should  normally  secrete  begin  to  accumulate  in  the  blood,  or  have  to 
seek  new  channels  for  their  escape,  the  vigor  of  the  intellect  is  at  once 
impaired.  It  is  with  the  brain  as  it  is  with  any  other  organ,  a  decline 
in  its  activity  is  soon  followed  by  a  deterioration  or  diminution  of  its 
structure,  and  we  must  not  forget  that  it  is  not  the  brain  which  accom- 
modates itself  to  the  capacity  of  the  skull,  but  the  skull  which  accommo- 
dates itself  to  the  shape  and  size  of  the  brain.  Whatever  the  causes  may 
be,  and  of  course  they  are  very  numerous,  which  tend  to  lessen  the  en- 
tire cerebral  mass,  or  by  inequality  in  their  effect  produce  the  develop- 
ment of  one  part  with  the  contemporaneous  diminution  of  another,  they 
will  inevitably  give  rise  to  a  modification  in  the  figure  of  the  skull ; 
and  observation,  as  well  as  phrenological  considerations,  would  cause  us 
to  anticipate  that,  if  the  effect  takes  place  in  such  a  way  as  to  involve  the 
higher  powers  of  intellection,  the  skull,  answering  in  its  change  thereto, 
will  assume  the  prognathous  cast. 

From  what  I  have  said  respecting  the  relationship  of  different  nations 
Hereditar  of  men,  it  will  be  gathered  that  the  peculiarities  on  which  we 
transmission  have  been  dwelling,  the  complexion  and  form  of  the  skull,  as 
of  variations.  Dependent  upon  hepatic  action,  are  capable  of  hereditary  trans- 
mission ;  for  such  a  modified  glandular  action,  in  whatever  manner  it 
may  have  been  occasioned,  can  be  propagated  in  that  way. 

In  these  remarks  it  will  be  perceived  that  I  have  mainly  had  in  view 
Base  form  of  that  degradation  from  the  more  perfect  standard  of  man  which 
from  low  Tern-  *s  encountered  in  hot  climates,  and  which  finds  its  expression 
peraturc.  in  a  blackness  of  the  skin  and  a  base  form  of  the  skull.  But 
there  is  likewise  a  white  degraded  form.  It  is  that  which  we  meet  in 
the  highest  latitudes,  and  it  is  therefore  dependent  upon  climate,  that  is 
to  say,  temperature.  Here  no  such  tax  is  thrown  upon  the  skin  as  is 
the  case  in  the  torrid  zone,  but  here  the  intellectual  powers  are  greatly 
enfeebled,  if  for  no  other  reason,  at  least  because  of  the  hardships  under 
which  life  must  be  maintained.  It  is  not,  therefore,  in  very  high  or  very 
low  latitudes  that  we  should  expect  to  find  man  in  his  best  estate,  and 
this  is  corroborated  by  the  history  of  all  races.  It  is  true  that,  by  the 
artificial  control  which  we  have  obtained  over  temperature  by  the  aid  of 
clothing  and  improved  modes  of  shelter,  we  have,  in  some  degree,  with- 
drawn ourselves  from  the  absolute  dominion  of  climate;  but,  putting 
these  disturbances  of  civilization  aside,  and  looking  only  to  our  natural 
state,  we  shall  be  constrained  to  admit  that  the  man  of  maximum  intel- 
lectual capacity  is  of  a  faint  brown  hue.  Nor  was  it  through  any  acci- 


DISAPPEARANCE   OF   THE   FAIR  RACES.  591 

dental  circumstance,  but  because  of  physiological  conditions,  Maximum  of 
that  civilization  arose  in  Egypt  and  in  the  Mesopotamian  J^falntbTovm 
countries.     It  was  for  a  like  physiological  reason  that  it  races. 
spread  next  through  the  nations  on  the  north  shore  of  the  Mediterranean, 
and  never  spontaneously  originated  in  Arctic  Europe  or  Tropical  Africa. 

Moreover,  it  must  be  observed  how  forcibly  the  doctrine  here  urged  of 
the  passage  of  man  from  one  complexion  to  another,  and  Disappearance 
through  successively  different  forms  of  skull  in  the  course  of  of  the  red-hair- 
ages,  is  illustrated  by  the  singular  circumstance  to  which  at-  eyed  people  in 
tention  has  of  late  years  been  directed,  of  the  gradual  disap-  Eur°Pe- 
pearance  of  the  red-haired  and  blue-eyed  men  from  Europe.  Less  than 
two  thousand  years  ago,  the  Homan  authors  bear  their  concurrent  testi- 
mony to  the  fact  that  the  inhabitants  of  Britain,  Gaul,  and  a  large  portion 
of  Germany  were  of  that  kind.  But  no  one  would  accept  such  a  descrip- 
tion as  correct  in  our  times.  By  some  writers,  who  have  not  taken  en- 
larged physiological  views,  this  curious  circumstance  has  been  attempted 
to  be  explained  on  the  hypothesis  of  a  more  prolific  power  of  the  brown 
or  black  haired  and  darker  man.  That  this  is  correct  not  a  shadow  of 
evidence  can  be  offered.  The  supplanting  of  the  red  by  the  black  haired 
man  is  neither  on  account  of  any  insidious  or  involuntary  extermination, 
nor  because  of  the  numerical  pressure  alluded  to.  The  true  Cause  of  thig 
reason  is  that  the  red-haired  man  has  himself  been  slowly  apparent  dis- 
changing  to  get  into  correspondence  with  the  conditions  that  appea 
have  been  introduced  through  the  gradual  spread  of  civilization — condi- 
tions of  a  purely  physical  kind,  and  with  which  the  darker  man  was  more 
nearly  in  unison ;  for  though  it  might  be  shown  that  the  climate  of 
Europe,  by  reason  of  the  removal  of  forests,  and  other  causes,  chiefly  agri- 
cultural in  their  nature,  has  undergone  a  change,  this  is  nothing  compared 
with  the  changes  that  have  been  accomplished  in  domestic  economy  by 
better  clothing,  and  more  comfortable  lodging  and  food,  and  these  are  par- 
allel to  actual  changes  in  climate.  What  a  contrast  between  the  starved, 
naked,  and  almost  houseless  peasant-savages  of  the  times  of  Ca3sar,  and 
the  well-fed,  well-clothed,  and  well-housed  agricultural  laborers  or  manur 
facturing  operatives  of  ours,  who,  though  they  may  be  living  in  the  same 
geographical  region,  are  literally  in  a  warmer  and  more  genial  climate — a 
climate  with  which  man  is  only  in  correspondence  when  his  skin  is  of  a 
darker  shade,  and  his  hair  of  a  brown  or  black  color ! 

From  these  investigations  of  the  anatomical  peculiarities  of  the  nations 
of  men,  we  may  turn  to  those  of  a  mental  kind,  which,  in-  Of  the  intellect 
deed,  are  derivatives  thereof.      Doubtless  the  intellectual  uai  qualities  of 
qualities  are  manifested  in  the  expression  of  the  countenance  natlons- 
and  in  the  capacity  and.  form  of  the  skull. 

Considering,  for  the  sake  of  convenience,  groups  of  nations  as  they 


592  MENTAL   QUALITIES   OF  THE   EUKOPEAN  AND   ASIATIC. 

are  distributed  geographically,  though,  as  we  have  seen,  this  is  a  divis- 
ion which  has  no  philosophical  foundation,  we  may  proceed  to  an  exam- 
ination of  the  psychical  state  of  the  European  and  Asiatic,  whose  history 
furnishes  us  abundant  materials  for  this  purpose.  The  black  nations  of 
Africa  and  the  red  tribes  of  America,  from  the  imperfect  advances  they 
have  made  toward  civilization,  can  supply  but  few  facts  for  such  an  in- 
vestigation. 

We  can  not  read  the  histories  of  Europe  and  Asia — we  can  not  exam- 
Synthetical  me  the  present  condition  of  those  continents,  without  coming 
mind  of  the  to  the  conclusion  that  the  people  inhabiting  them  possess  a 
lyticai  mind  of  different  mental  constitution.  After  what  has  been  said  re- 
the  European.  Specting  the  influence  of  physical  circumstances  on  the  or- 
ganization of  man,  it  is  unnecessary  for  us  to  inquire  here  in  what  that 
difference  has  originated.  It  is,  perhaps,  most  significantly  expressed 
if  we  say  that  the  mind  of  the  Asiatic  is  essentially  synthetic,  that  of  the 
European  analytic.  The  former  is  the  creator  of  systems  of  theology, 
law,  science,  some  of  which  have  endured  for  thousands  of  years,  and 
have  been  adopted  by  a  large  portion  of  the  human  race.  The  latter 
pursues  his  course  in  a  way  less  grand,  but  which,  since  it  has  a  better 
ascertained  foundation,  leads  to  more  certain,  and,  in  the  course  of  cen- 
turies, will  show  more  powerful,  widespread,  and  equally  lasting  results. 
The  intellectual  peculiarity  of  the  Asiatic  has  been  attended  with  the  ad- 
vantage of  producing  an  almost  definite  social  state.  In  Asia  the  cus- 
toms remain  invariable ;  every  thing  is  in  a  state,  as  we  might  term  it, 
of  stagnation,  or,  as  they  consider  it,  of  repose.  On  the  other  hand,  the 
analytical  tendency  of  the  European  has  led  to  the  intellectual  and  polit- 
ical anarchy  of  our  times,  when  fundamental  doctrines  of  every  kind  are 
called  in  question,  and  scarcely  two  men  can  be  found  whose  views  on  re- 
ligious, political,  and  social  questions  coincide.  In  Asia  there  are  no 
questions,  but  only  affirmations.  Europe,  except  when  the  Church  for 
a  thousand  years  enforced  the  Asiatic  system,  has  ever  been  prone  to  ask 
questions.  Since  the  fourteenth  century,  when  she  returned  to  this  pro- 
pensity, she  has  been  passing  through  a  chaos  of  doubt  in  the  innumer- 
able answers  she  receives. 

With  an  intellect  of  this  analytical  kind,  it  may  be  doubtful  whether 
Necessity  of  the  European  could  ever  have  spontaneously  entered  on  the 
Europ^aiTdv-  career  °f  civilization.  The  contact  of  the  Asiatic  was  essen- 
iiization.  tial  to  him,  as  giving  him  the  material  on  which  to  work. 
Nor  was  it  of  importance  whether  the  basis  from  which  he  thus  started, 
and  the  additions  which,  from  time  to  time,  he  has  received,  were  true  or 
false ;  they  furnished  him  with  the  essential  condition  that  was  wanting. 
The  dissector  must  have  his  subject.  The  history  of  Europe,  whether 
as  regards  philosophical,  religious,  or  political  affairs,  bears  the  impress 


INFLUENCE   OF  EUEOPE   AND  ASIA  ON   AFKICA.  593 

of  the  analytical  mind  of  the  white  man.  In  Asia,  on  all  these  points 
they  tend  to  the  homogeneous.  In  Europe,  every  day  makes  us  more 
and  more  heterogeneous. 

Thus  compared  with  that  of  the  Asiatic,  it  can  not  be  denied  that  the 
mind  of  the  European  is  of  the  higher  order.    Moreover,  though  Comparison 
our  moral  qualities  are  not  equal  to  our  intellectual,  the  man-  J^Euro^ean 
ner  in  which  we  act  in  the  conditions  in  which  we  are  placed  intellect, 
asserts  our  superiority  even  in  that  regard.     The  instances  are  many  in 
which  we  do  not  dare  to  cany  our  convictions  into  execution,  and  each 
of  these  illustrates  the  inequality  here  set  forth.     To  "be  content  with  the 
chances  of  things,  to  suffer  the  events  of  life  uncomplainingly,  is  surely 
not  so  worthy  a  character  as  to  demand  a  reason,  and  to  accept  the  con- 
sequences of  resistance. 

The  intellectual  superiority  of  the  European  over  the  Asiatic  is  strik- 
ingly illustrated  by  their  relative  power  over  the  African,  who  Th  . 
is  confessedly,  in  this  respect,  beneath  them  both.  To  go  no  ive  influence 
farther  back  than  the  last  ten  centuries,  both  have,  in  their  on  Afnca- 
special  way,  exerted  their  influence.  Here  and  there,  on  the  outskirts 
of  that  great  continent,  the  European  has  made  a  faint,  but,  at  the  best, 
only  a  transitory  impression :  the  Asiatic  has  pervaded  it  through  and 
through.  Of  the  promising  churches,  which,  in  the  early  days  of  Chris- 
tianity, fringed  the  northern  coast,  scarce  any  vestige  now  remains  ;  the 
faith  of  Arabia  has  not  only  supplanted  them,  but  is  spreading  even  to- 
ward the  Cape  of  Good  Hope,  and  this,  as  it  would  appear,  spontaneous- 
ly. On  the  other  hand,  the  European,  with  that  universal  charity  which 
is  his  noblest  attribute,  has  spared  no  exertions  and  no  expense  to  dif- 
fuse the  blessings  which  have  been  conferred  by  Providence  upon  him ; 
and  yet  it  would  seem  to  be  in  vain,  though  enforced  by  the  great  exam- 
ple of  his  civilization  and  power.  In  this  we  see  the  affinity  of  the  mind 
of  Africa  with  that  of  Asia,  of  which  it  is  an  exaggeration,  and  its  incon- 
gruity with  that  of  Europe.  It  can  not,  in  its  present  state,  appreciate 
our  manner  of  thinking ;  it  can  not  embrace  our  conceptions  of  truth,  but 
delivers  itself  unresistingly  to  the  dogmas  of  the  East,  with  all  their  er- 
rors of  faith  and  all  their  imperfections  of  polity.  * 

Since  I  have  been  drawn  into  a  psychical  comparison  of  the  Asiatic 
and  European  in  the  foregoing  particulars,  it  may  not  be  positionof 
amiss  to  consider  the  two  races  in  another  important  respect,  women  in  Asia 
the  condition  of  their  females.     In  the  barbarous  state,  the  a 
woman  is  the  slave  of  the  man  ;  the  Mohammedan  makes  her  his  toy,  the 
European  his  companion.     The  avarice  of  the  former  for  beauty  is  re- 
placed in  the  latter  by  an  avarice  for  wealth.     The  treasures  of  the  one 
are  placed  in  a  harem ;  those  of  the  other  are  perhaps  invested  in  the 
public  stocks. 

PP 


594  POLYGAMY  AND   MONOGAMY. 

The  natural  position  of  the  female  sex  in  this  respect  is  indicated  at 
once  by  the  relation  of  numbers.  In  Europe,  for  every  106  male  births 
there  are  100  female,  and  as  the  sex  of  offspring  is  influenced  by  the 
relative  ages  of  the  parents,  the  older  parent  giving  a  tendency  to  its  own 
sex,  we  may  reasonably  suppose  that  in  the  infants  born  of  polygamy 
the  males  will  preponderate,  reversing  the  result  which  is  observed  in  the 
great  cities  of  Western  Europe,  in  which  the  ratio  of  female  births  rises 
above  its  true  mean  by  nearly  four  per  cent,  when  those  births  are  ille- 
gitimate. In  that  term  of  the  market,  four  per  cent.,  what  a  volume  of 
information  is  here  conveyed !  It  tells  us  that  the  European  female  does 
not  fall  at  once ;  that  there  intervene  years  of  resistance  to  temptation,  a 
struggle  of  virtue  against  penury  and  distress,  but  it  also  reveals  the 
precocious  wickedness  of  man ! 

Considering,  therefore,  the  near  equality  of  male  and  female  births,  we 
may  truly  assert  that  monogamy  is  the  proper  condition  of  our  species, 
and  that,  apart  from  its  social  evils  and  criminality,  polygamy  is  an  un- 
natural state.  I  shall  pass,  as  unworthy  of  notice,  the  assertion  of  those 
who,  in  this  Christian  country,  practice  so  shameful  a  vice,  that  we  might 
as  well  divide  the  number  of  square  acres  on  the  face  of  the  globe  by  the 
number  of  its  inhabitants,  and  declare  it  to  be  immoral  in  any  one  to 
possess  a  larger  estate  than  corresponds  to  the  quotient  thereof.  Ac- 
knowledging the  natural  depravity  of  the  human  heart,  I  accept  with 
humiliation  the  rebuke  that  the  most  enlightened  communities  exhibit 
in  these  respects  a  deplorable  spectacle,  and  that  the  vices  of  the  Mo- 
hammedan harems  find  their  full  counterpoise  in  the  general,  the  awful, 
and,  in  many  places,  the  legalized  prostitution  of  Christian  cities. 

Europe  has  adopted  as  the  fundamental  basis  of  its  religious:  system 
Effects  of  o-  *ke  Sran^  Asiatic  truth  of  the  unity  of  God,  but  in  its  family 
lygamy  and  system  it  has  rejected  the  immemorial  and  widespread  Asi- 
mogamy.  ^^  practjce  Of  polygamy.  That  circumstance  has  made  it 
what  it  is.  The  monogamous  habit  has  tended  to  draw  the  family  tie 
more  firmly,  and  has  led  to  the  accumulation  and  transmission  of  wealth 
from  generation  to  generation  in  the  same  house.  "With  this  have  arisen 
a  liability  to  concentration  of  power  in  castes,  and  the  use  of  surnames 
which  have  perpetuated  family  interests  and  family  pride.  In  Europe 
the  career  of  improvement  is  in  the  society ;  in  Asia  it  is  in  the  individ- 
ual ;  the  unknown,  starving,  illiterate,  but  strong-willed  soldier  of  to-day 
is  the  Pasha,  the  Caliph,  the  Emperor  to-morrow.  The  castes  of  India 
The  respective  form  but  a  trifling  exception  to  the  fact  that,  in  the  midst  of 
STandEu-  a  uinversal  despotism,  the  primest  democratic  element  is 
rope.  concealed,  for  the  career  is  open  to  talent.  Through  this, 

Asia  has  asserted  her  superiority  again  and  again.  Europe  has  never 
produced  a  great  lawgiver ;  Asia  has  produced  many.  Generations  of 


ASIATIC  CONTRIBUTIONS  TO   CIVILIZATION.  595 

three  hundred  millions  of  men  have  followed  the  maxims  of  Confucius  for 
two  thousand  years,  three  hundred  millions  are  the  followers  of  Moham- 
med. The  faiths  which  govern  the  daily  life  of  two  thirds  of  the  human 
race  may  well  be  an  awful  spectacle  to  us — the  more  awful  because  we 
know  that  they  are  a  delusion.  The  only  approach  to  these  great  results 
in  the  Western  Continent  is  in  the  supremacy  of  the  Italian  Church ;  but 
Rome  owed  the  origin  of  her  system  to  Asiatic  missionaries ;  nor  was  it 
the  completed  work  of  the  hand  of  one  man,  it  was  the  offspring  of  cen- 
turies, the  joint  issue  of  a  long  line  of  illustrious  sacerdotal  kings.  In 
military  life  the  highest  qualities  shine  forth.  If  the  talent  for  command 
and  the  capacity  of  a  statesman  are  to  be  measured  by  the  grandeur  of  un- 
dertakings and  their  success,  it  still  remains  for  Europe  to  produce  a  sol- 
dier the  equal  of  Genghis  Khan,  and  a  king  like  Tamerlane.  These  great 
captains  held  almost  all  Asia  in  their  iron  grasp.  The  opinions  we  com- 
monly hold  respecting  these  illustrious  men  have  come  to  us  through 
perverted  channels.  Such  prodigious  successes  as  theirs  imply  the  high- 
est intellectual  powers.  Their  true  character  appears  when  we  compare 
them  with  their  European  contemporaries.  At  the  same  time  that 
Charles  VII.  of  France  was  mystifying  his  people  with  the  imposture  of 
Joan  of  Arc,  and  Henry  VI.  of  England  was  engaged  in  the  burning  of 
necromancers  who  had  attempted  his  life  by  melting  an  enchanted  wax 
image  before  the  fire,  Ulug  Beg,  the  grandson  of  Tamerlane,  was  de- 
termining with  precision  the  latitude  of  Samarcand,  his  capital,  with  a 
mural  quadrant  of  180  feet  radius,  and  making  a  catalogue  of  the  stars 
from  his  own  observations,  which  more  than  200  years  subsequently  was 
printed  at  the  University  of  Oxford. 

If  the  European  wishes  to  know  how  much  he  owes  to  the  Asiatic,  he 
has  only  to  cast  a  glance  at  an  hour  of  his  daily  life.  The  Contributions 
clock  which  summons  him  from  his  bed  in  the  morning  was  °* Em-^ean0 
-the  invention  of  the  East,  as  were  also  clepsydras  and  sun-  civilization, 
dials.  The  prayer  for  his  daily  bread  which  he  has  said  from  his  in- 
fancy first  rose  from  the  side  of  a  Syrian  mountain.  The  linens  and 
cottons  with  which  he  clothes  himself,  though  they  may  be  very  fine,  are 
inferior  to  those  which  have  been  made  time  immemorial  in  the  looms  of 
India.  The  silk  was  stolen  by  some  missionaries,  for  his  benefit,  from 
China.  He  could  buy  better  steel  than  that  with  which  he  shaves  him- 
self in  the  old  city  of  Damascus,  where  it  was  first  invented.  The  cof- 
fee he  expects  at  breakfast  was  first  grown  by  the  Arabians,  and  the  na- 
tives of  Upper  India  prepared  the  sugar  with  which  he  sweetens  it,  a 
schoolboy  can  tell  the  meaning  of  the  Sanscrit  words  sacchara  canda. 
If  his  tastes  are  light,  and  lie  prefers  tea,  the  virtues  of  that  excellent 
leaf  were  first  pointed  out  by  the  industrious  Chinese.  They  also 
taught  him  how  to  make  and  use  the  cup  and  saucer  in  which  to  serve 


596  ASIATIC  CONTRIBUTIONS  TO   ART  AND  SCIENCE. 

it.  His  breakfast- tray  was  lacquered  in  Japan.  There  is  a  tradition 
that  leavened  bread  was  first  made  of  the  waters  of  the  Ganges.  The 
egg  he  is  breaking  was  laid  by  a  fowl  whose  ancestors  were  domesticated 
by  the  Malaccans,  unless  she  may  have  been,  though  that  will  not  alter 
the  case,  a  modern  Shanghai.  If  there  are  preserves  and  fruits  on  his 
board,  let  him  remember  with  thankfulness  that  Persia  first  gave  him 
the  .cherry,  the  peach,  the  plum.  If  in  any  of  those  delicate  preparations 
he  detects  the  flavor  of  alcohol,  let  it  remind  him  that  that  substance  was 
first  distilled  by  the  Arabians,  who  have  set  him  the  praiseworthy  exam- 
ple, which  it  will  be  for  his  benefit  to  follow,  of  abstaining  from  its  use. 
When  he  talks  about  coffee  and  alcohol,  he  is  using  Arabic  words.  A 
thousand  years  before  it  had  occurred  to  him  to  enact  laws  of  restriction 
on  the  use  of  intoxicating  drinks,  the  Prophet  of  Mecca  had  accomplish- 
ed the  same  object,  and,  what  is  more  to  the  purpose,  has  compelled,  to 
this  day,  all  Asia  and  Africa  to  obey  it.  We  gratify  our  taste  for  per- 
sonal ornament  in  the  way  the  Orientals  have  taught  us,  with  pearls,  ru- 
bies, sapphires,  diamonds.  Of  public  amusements  it  is  -the  same :  the 
most  magnificent  fireworks  are  still  to  be  seen  in  India  and  China ;  and 
as  regards  the  pastimes  of  private  life,  Europe  has  produced  no  invention 
Asiatic  contri-  which  can  rival  the  game  of  chess.  We  have  no  hydraulic 
buttons  in  art.  constructions  as  great  as  the  Chinese  canal — no  fortifications 
as  extensive  as  the  Chinese  wall ;  we  have  no  artesian  wells  that  can  at 
all  approach  in  depth  some  of  theirs ;  we  have  not  yet  resorted  to  the 
practice  of  obtaining  coal-gas  from  the  interior  of  the  earth :  they  have 
borings  for  that  purpose  more  than  3000  feet  deep. 

Similar  observations  may  be  made  if  we  examine  the  Asiatic  contribu- 
Asiatic  contri  ^ons  to  science»  While  the  learned  of  Europe  were  forbid- 
butions  in  sci-  ding,  as  a  heresy,  the  doctrine  of  the  globular  figure  of  the 
earth,  the  Caliph  Al  Maimon  was  measuring  the  length  of  a 
degree  along  the  shore  of  the  Eed  Sea.  He  and  his  successors  repeat- 
edly determined  the  obliquity  of  the  ecliptic.  A  Saracen  constructed  the 
first  table  of  sines,  another  explained  the  nature  of  twilight,  and  showed 
the  importance  of  allowing  for  atmospheric  refraction  in  astronomical  ob- 
servations. Algebra  itself  was  invented  and  brought  into  Europe  by  the 
Mohammedans,  who  gave  it  the  name  it  bears.  The  same  may  be  said 
of  chemistry.  It  is  needless  to  pursue  these  statements,  for  whoever  will 
take  the  trouble  to  look  into  the  history  of  any  branch  of  science  existing 
in  the  seventeenth  century  will  find  how  deep  are  its  obligations  to  Asia. 
I  shall  therefore  add  but  one  fact  more,  the  invention  of  the  figures  of 
arithmetic,  which  in  reality  gave  birth  to  that  science,  and  laid  knowl- 
edge and  commerce  equally  under  obligations.  From  its  simplicity, 
beauty,  and  universality,  this  invention  alone  is  enough  to  command  the 
gratitude  of  the  human  race.  The  manner  of  using  the  cipher  and 


SPEEAD   OF   MOHAMMEDANISM   IN  AFEICA.  597 

placing  the  figures  is  one  of  the  happiest  suggestions  of  the  genius  of 
man. 

I  shall  not  set  in  contrast  with  these  statements  a  catalogue  of  the 
contributions  of  the  European.  We  know  our  own  doings  well  enough  ; 
but  such  facts  as  the  preceding  may  serve  to  remind  us  that  the  Euro- 
pean is  no  more  justified  in  ignoring  the  obligations  he  is  under  to  the 
Asiatic  than  the  Asiatic  is  justified  in  regarding  him  as  a  barbarian. 
In  the  advance  of  our  common  humanity,  both  have  taken  and  still  are 
taking  their  share.  The  European  has  brought  to  the  new  continent  he 
discovered  his  religion,  his  laws,  his  literature,  his  science,  and  it  may  be 
a  profitable  subject  of  reflection  to  him  that  under  them  the  Indian  is  dy- 
ing away.  The  Asiatic  has  likewise  carried  the  Koran  into  The  g  rpad  of 
Africa.  Our  prejudices  and  education  ought  not  to  conceal  Mohammedan- 
from  us  that  there  must  surely  be  some  adaptedness,  even  lsm 
if  it  be  in  a  sensual  respect,  between  its  doctrines  and  the  ideas  of  many 
climates,  many  nations,  many  colors.  The  light  of  the  Arabian  crescent 
shines  on  all  countries  from  the  Gulf  of  Guinea  to  the  Chinese  wall.  In 
those  pestilential  and  sun-burnt  forests  under  the  equinoctial  line,  cit- 
ies are  springing  up  with  their  ten,  their  twenty,  their  fifty  thousand  in- 
habitants. That  implies  subordination,  law,  civilization.  It  may  be 
that  this  is  not  a  course  of  events  which  would  have  been  chosen  by 
the  French  on  the  north,  with  their  military  colonies  ;  the  English  on  the 
south,  with  their  commercial  establishments ;  the  Americans  on  the  west, 
with  their  political  institutions ;  but  it  is  the  course  of  Providence.  Let 
us  be  thankful  if  the  African  is  rescued  from  the  abyss  of  barbarism,  and 
brought  to  a  knowledge  of  our  higher  morality  and  holier  religion,  as 
brought  he  will  be  at  last,  even  though  it  be  by  the  hand  of  the  Prophet. 

In  the  following  chapter  I  shall  have  some  remarks  to  make  respect- 
ing the  manner  in  which  the  civilization  of  Europe  was  ac-  p  ectiv 
complished,  and  shall  offer  reasons  for  supposing  that  its  es-  civilization  of 
sential  condition  was  a  physiological  change  in  the  inhabit- 
ants. Without  troubling  the  reader  with  details,  I  may  here  incident- 
ally observe  that  the  spread  of  Mohammedanism  in  Africa  is  altogether 
owing  to  its  having  been  introduced  in  the  right  direction.  It  appears  to 
me  hopeless  to  attempt  the  amelioration  of  that  continent  from  its  west- 
ern shore.  Whatever  is  done  must  be  done  from  the  East.  In  power 
of  intellect,  and  in  a  disposition  to  appreciate  our  civilization,  the  inhab- 
itants of  the  countries  bordering  on  the  Red  Sea  are  far  superior  to 
those  on  the  Atlantic.  It  does  not  seem  well  to  begin  with  those  who 
are  the  least  prepared.  We  do  not  commonly  expect  success  from 
operations  conducted  at  an  eccentric  point.  The  Koran  has  spread  be- 
cause it  has  availed  itself  of  the  great  lines  of  trade,  which  reach  from 
the  Red  Sea  to  the  interior  of  the  continent;  it  has  spread,  not  because 


598  SPREAD   OF   CHRISTIANITY   IN    AMERICA. 

of  its  doctrinal  theology  or  theoretical  politics,  but  because  it  is  concern- 
ed in  the  amendment  of  the  social  condition  of  the  people.  That  is  pre- 
cisely the  principle  which  accomplished  the  civilization  of  Europe  ;  and, 
with  regard  to  the  capacity  of  those  nations  to  receive  Christianity,  we 
may,  even  to  our  shame,  recall  the  circumstance  that  the  Abyssinians  are 
yet  a  Christian  people,  still  retaining  the  ancient  faith  delivered  to  them 
in  the  apostolic  ages,  when  our  forefathers  were  pagan  barbarians.  Sur- 
rounded by  the  most  depressing  and  antagonizing  influences,  they  have 
held  fast  to  their  faith  for  nearly  eighteen  centuries.  The  hoary  Abys- 
sinian Church  carries  us  back  beyond  the  Council  of  Chalcedon  and  the 
disputes  of  the  Eutychians ;  its  literature  is  full  of  the  questions  which 
exercised  the  faithful  in  the  primitive  times  of  the  brethren  at  Jerusalem 
— circumcision,  things  strangled,  meats  prohibited  by  the  law  of  Moses  ; 
and  yet,  to  the  discredit  of  the  European  and  American,  it  must  be  said 
that  this  Church,  full  of  incidents  of  the  most  singular  and  touching  in- 
terest, has  scarcely  had  (with  one  exception)  any  sympathy  extended  to 
it  by  other  Christian  people. 

From  these  considerations  of  the  effects  of  Asiatic  civilization  upon 
Spread  of  Africa,  we  may  profitably  turn  to  a  brief  statement  of  that  of 
^/t^Amer"  Eur°Pe  uPon  tne  red  races  of  America.  This  result  in  the 
icas.  two  continents,  north  and  south,  is,  that  in  the  latter,  out  of 

almost  1,700,000  aborigines,  nearly  1,600,000  have  embraced  Christian- 
ity, less  than  100,000  remaining  in  the  savage  state.  No  such  favorable 
impression  has  been  made  upon  the  aborigines  of  the  northern  continent, 
who,  as  is  well  known,  are  steadily  diminishing  in  numbers,  and  many 
tribes  that  were  once  numerous  have  disappeared.  This  has  taken  place 
notwithstanding  the  care  which  has  been  manifested  by  the  government 
of  the  United  States  for  all  those  who  are  within  its  territories.  It  does 
not  appear  that  the  conclusion  which  has  been  drawn  by  some  eminent 
authors  in  view  of  these  facts  can  be  maintained,  that  "  this  considera- 
tion, if  we  can  separate  it  from  the  events  of  the  Spanish  conquest,  for 
which  it  is  to  be  hoped  that  the  soldiers,  and  not  the  ministers  of  relig- 
ion, are  responsible,  must  be  allowed  to  reflect  honor  on  the  Eoman  Cath- 
olic Church,  and  cast  a  deep  shade  on  the  history  of  Protestantism." 

That  this  conclusion  is  incorrect  is  shown  at  once  by  the  very  tables 
that  are  relied  on  for  its  support.  Out  of  the  100,000  aborigines  of 
South  America  who  remain  heathen,  more  than  66,000,  that  is  to  say, 
two  thirds,  belong  to  the  Araucanian  and  Patagonian  branches,  who  are 
the  counterparts  for  that  continent  of  the  Indians  of  the  United  States 
and  British  American  territories  in  this.  Upon  these  it  may  be  truly 
said  that  no  impression  whatever  has  been  made:  Of  the  Patagonian 
branch,  estimated  at  more  than  32,000,  only  100  individuals  are  stated 
to  have  embraced  Christianity,  and  of  the  Araucanian  branch,  consisting 


EFFECT   OF   CLIMATE   ON   CIVILIZATION.  599 

of  34,000,  not  one.  It  is  by  bringing  into  these  discussions  the  singu- 
lar and  widespread  error  that  all  the  aboriginal  American  tribes  are 
alike,  and  by  not  making  due  allowance  for  their  habits  of  life,  their 
physical  and  mental  endowments,  that  this  mistake  has  arisen;  but 
whoever  will  consider  the  facts  as  they  actually  stand  must  come  to  the 
conclusion  that  there  are  just  as  well-marked  differences  among  these 
people  as  there  are  in  the  climates  and  circumstances  in  which  they  live. 
Intellectually,  there  is  even  a  greater  difference  between  the  Indian  of 
the  United  States  and  the  Indian  of  Peru  than  there  is  in  their  physical 
aspect.  The  one  is  an  intractable  savage,  the  other  docile  and  easily 
led;  the  one  has  never  yet  been  enslaved,  the  other  prospers  and  in- 
creases in  number,  though  he  has  sustained  all  the  consequences  of  the 
atrocities  of  the  Spanish  Conquest.  By  chance,  or  perhaps,  as  we  should 
more  truly  say,  through  Providence,  the  field  of  Catholic  labor  has  been 
among  the  more  docile  races,  that  of  Protestant  among  the  more  untam- 
able, and  the  result  is  exactly  such  as,  under  those  circumstances,  the 
philosopher  would  be  led  to  expect. 

I  can  not  here  avoid  recalling  to  the  attention  of  the  reader  what  I  have 
said  respecting  the  comparative  progress  of  Christianity  and  Mohammed- 
anism in  Africa,  for  we  find  upon  our  own  continent  a  repetition  of  the 
facts  which  were  presented  to  us  there.  The  chances,  if  such  a  term  can, 
on  this  occasion,  with  propriety  be  used,  of  the  diffusion  of  Christian  civ- 
ilization, are  directly  proportional  to  the  existing  intellectual  development 
of  the  community  among  whom  the  attempt  is  made.  Mohammedanism 
has  diffused  itself  in  Africa  for  precisely  the  same  reason  that  Catholi- 
cism has  succeeded  in  America— because  its  operation  was  commenced 
upon  those  tribes  best  prepared  to  receive  it. 

We  can  not  have  a  more  striking  instance  of  the  effect  of  climate  on 
civilization  than  that  which  is  offered  by  the  American  In-  Illustration  of 
dians.  As  is  well  known,  though  throughout  all  those  lati- 
tudes in  which  life  is  maintained  with  difficulty,  by  reason  iiizatkm. 
of  their  inclemency,  all  the  tribes,  both  of  the  north  and  south  continent, 
were  in  a  barbarous  state,  yet  in  those  more  pleasant  countries  toward 
the  equator,  in  which,  by  reason  of  the  natural  fertility  of  the  soil  and  a 
higher  mean  temperature,  the  inhabitants  had  little  occasion  to  work,  and 
passed  their  lives  in  comparative  plenty  and  ease,  a  special  civilization 
had  arisen.  It  is  of  no  little  interest  to  observe  how  the  main  features 
of  Asiatic  and  European  civilization  were  presented  in  this  case,  doubt- 
less without  any  communication  with  those  continents,  for  it  shows  how 
the  human  mind  is  ever  prone  to  unfold  itself  in  the  same  way,  to  give 
birth  to  the  same  ideas  and  to  the  same  inventions.  The  „.  .,. 

Civilization  of 

civilized  Americans  of  Mexico  and  Peru  were  organized  in  the  tropical  in- 
communities  not  unlike  those  with  which  the  white  man  is  dians* 


(300  EXTINCTION   OF   THE    INDIANS. 

elsewhere  familiar,  living  in  cities  which  were  regulated  by  municipal 
laws  familiar  enough  to  us,  maintaining  among  their  social  institutions, 
fixed  ideas  respecting  property  and  family  rights,  having  a  national  relig- 
ion, an  established  priesthood,  and  the  means  of  recording  events,  which, 
though  imperfect,  were  not  unlike  those  which  obtained  in  the  earlier  pe- 
riods of  our  own  civilization..  If  they  had  not  a  knowledge  of  iron  and 
the  plow,  they  had  already  fallen  upon  the  early  Asiatic  plan  of  subju- 
gating and  domesticating  such  animals  as  were  suitable  for  their  pur- 
poses. Civilization  arose  among  these  people  in  similar  localities  and 
under  similar  circumstances  of  life  as  it  had  arisen  among  our  ancestors 
in  the  Old  World,  and,  such  is  the  sameness  of  constitution  of  the  human 
mind,  was  advancing  in  exactly  the  same  way. 

Although,  for  a  time,  among  the  degenerate  descendants  of  the  Span- 
Gradual  ex-  iards,  the  South  American  Indian  may  maintain  himself,  but 
tinction  °f  the  little  doubt  can  be  entertained  that  the  same  destiny  awaits 
temperate  him  which  has  befallen  his  North  American  brother.  He 


zone. 


can  not  withstand  that  enterprise  and  activity  which  are 
leading  to  the  extension  of  the  white  invaders  of  his  native  soil.  Even 
though  the  age  of  cruelty  to  these  unfortunates  has  passed  away,  never 
more  to  return,  and  enlightened  governments,  animated  by  sentiments 
into  which  no  mercenary  consideration  enters,  interest  themselves  in  their 
welfare,  it  is  not  to  be  supposed  that  nations  depending  on  such  an  arti- 
ficial support  can  long  continue  to  exist.  In  this  inevitable  decline,  the 
tropical  races  may  far  more  worthily  excite  our  commiseration  than  those 
of  the  higher  latitudes ;  nor  is  their  departure  unavenged :  they  leave 
behind  them  two  curses,  tobacco  and  syphilis. 

In  conclusion  of  this  partial  examination  of  the  progress  of  the  human 
Manner  of  family  under  varied  circumstances,  we  may  remark  a  repeti- 
natlo^rin^v-  ^on  °^  a  ^6  series  of  changes  to  those  which  have  been 
ilization.  traced  in  the  psychical  career  of  the  individual,  and  this, 
whether  we  consider  the  progress  in  theology,  policy,  philosophy,  or  any 
other  respect.  It  is  a  continued  passage  from  the  general  to  the  special 
— from  the  homogeneous  to  the  heterogeneous.  The  history  of  any  of 
the  ancient  nations  might  be  brought  forward  as  an  example.  Emerging 
from  the  barbarous  state,  they  shake  off  their  Fetichism,  that  union  of 
the  supernatural  with  the  natural,  which  gives  to  every  wood,  every  tree, 
every  river,  its  presiding  genius ;  to  families,  their  Penates ;  to  the  city, 
and  even  to  the  road,  their  Lares ;  to  stars,  and  to  stones,  and  to  med- 
icines, their  spirits ;  to  the  night,  its  apparitions  and  fairies.  It  is  in 
vain  that  we  say  these  are  the  subjects  of  African  credulity.  They  are 
found  in  the  origin  of  all  people.  Our  forefathers  once  cherished  the  il- 
lusions which  still  occupy  the  negro  mind.  The  time  came  when  intel- 
lectual development  outgrew  such  base  superstitions,  and  for  a  crowd  of 


PROGRESS   OF  CIVILIZATION.  601 

imaginary  inanities  were  substituted  the  chosen  forms  of  Polytheism.  It 
is  true  that,  among  Egyptians,  Hindoos,  or  Greeks,  there  were  deities 
enough,  but  the  process  of  specialization  may  be  nevertheless  plainly  dis- 
cerned. The  Fetich  stage,  the  Polytheistic  stage,  are  necessarily  in- 
cluded in  the  onward  progress  to  a  pure  metaphysical  Monotheistic  con- 
ception. In  this  it  is  to  be  remarked  that  the  Asiatic  races  Their  religious 
of  men  have  led  the  way,  both  in  the  priority  and  strictness  Persuasions. 
of  their  views.  The  great  statesmen  of  China,  of  India,  of  Arabia,  and 
of  Judea,  centuries  ago,  seized  upon  this  as  the  pivot  of  their  intellectu- 
al and  even  political  systems.  To  the  last  country,  Europe  itself,  as 
history  proves,  is  indebted  for  this  noble  idea. 

European  Monotheism  is  not  indigenous,  but  imported  from  the  He- 
brews, an  Asiatic  race.  The  intellectual  condition  of  the  nations  among 
whom  it  was  introduced  was  but  little  advanced,  and  hence  among  some 
it  came  to  be  degraded— mixed  up  with  the  remains  of  popular  and  an- 
thropomorphic conceptions,  which  otherwise  were  gradually  dying  out. 
For  a  length  of  time  the  pagan  creeds  maintained  a  conflict  with  it,  and 
with  difficulty  it  disentangled  itself  from  the  base  features  wThich  they 
endeavored  to  impress  upon  it,  as  with  the  Hebrews  themselves  of  old, 
the  people  seemed  to  be  reluctant  to  surrender  altogether  their  Polythe- 
istic ideas. 

These  remarks  are  to  be  understood  as  not  applying  to  individuals, 
for  in  every  age  and  nation  great  men  have  arisen,  whose  views  on  these 
and  other  subjects  of  like  vital  importance  were  far  in  advance  of  their 
times.  In  their  best  days,  both  in  Greece  and  Kome,  there  were  men 
who  had  attained  to  the  standard  here  alluded  to,  but  their  teaching  was 
without  effect  on  the  popular  mass.  There  was  a  want  of  equivalency 
between  the  individual  attainment  and  the  race  attainment.  Though 
individuals  may  be  progressive,  races  are  essentially  conservative ;  and 
hence  there  will  constantly  arise  against  individual  attempts  at  an  ad- 
vance discountenance  and  resistance,  an  opposition  which  in  too  many 
instances  becomes  a  tyranny.  Masses  of  men  are  not  like  inorganic  mass- 
es, which  resist  a  change  by  their  inertia  alone.  The  biography  of  ev- 
ery great  reformer  shows  that  the  popular  mind  resents  any  disturbance 
of  its  repose.  [Resistance  has  to  be  overcome  in  the  moving  of  things, 
resentment  is  added  in  the  moving  of  men. 

To  the  philanthropist  it  is  a  most  delightful  spectacle  that  the  various 
nations,  in  spite  of  the  difference  of  their  interests,  their  Existence  of  a 
creeds,  and  their  politics,  can  yet  present  certain  great  prin-  ^iTty  wit™'dis- 
ciples  which  they  recognize  in  common,  and  this  is  becom-  cordant  creeds. 
ing  more  and  more  marked  with  the  onward  advance  of  the  world.  In 
the  course  of  events,  the  special  is  ever  coming  out  of  the  general,  and 
the  great  principles  of  a  common  morality  are  gradually  disentangling  and 


602  SOCIAL   MECHANICS. 

unfolding  themselves  from  contradictory  forms  of  faith.  The  Chinese, 
the  Hindoo,  or  the  Turk,  though  they  may  not  coincide  with  the  Amer- 
ican or  European  as  to  what  is  to  be  looked  upon  as  true,  will  yet  agree 
as  to  what  is  just.  The  sentiment  of  honor,  the  ideas  of  personal  integ- 
rity, are  fast  becoming  universal. 

Yet  even  in  these  later  ages,  there  is  in  this  respect  nothing  new.  The 
tendency  of  the  human  mind,  whether  individual  or  collective,  to  the  same 
direction  is  continually  manifest — a  premarked  and  predestined  course 
in  which  it  must  go.  Our  most  refined  notions  of  rectitude  contain  noth- 
ing more  than  is  to  be  found  in  the  little  epitome  of  the  ancient  lawgiv- 
er; for  if  we  strike  from  the  ten  commandments  \vhatever  is  explanatory 
or  threatening,  retaining  the  mandatory  parts  alone,  there  remains  what 
commends  itself  to  the  understanding  of  intelligent  men  even  of  the 
most  diverse  nations — the  acknowledgment  of  the  unity  of  God,  the  ven- 
eration due  to  him,  the  expediency  of  a  day  of  rest  for  the  laborer,  the 
duty  of  filial  affection,  the  enormity  of  murder,  the  sin  of  adultery,  the 
crime  of  stealing,  the  shame  of  lying,  and  a  strict  regard  for  the  property 
of  another :  these  are  things  which  exact  for  themselves  a  spontaneous 
and  universal  assent. 


CHAPTER  VIII. 

SOCIAL  MECHANICS. 

Comparative  Sociology. —  Connection  of  Structure  and  Habit. —  Connection  of  History  and  Phys- 
iology.—  Insect  Society. — Descartes 's  Doctrine  that  Insects  are  Automata. — Necessity  of  a 
Mechanism  of  Registry  for  Instinct,  Reason,  and  Civilization. 

Nature  of  Man. — Influence  of  surrounding  Circumstances  on  him. — Deflniteness  of  his  Career. 

GENERAL  FACTS  OF  EUROPEAN  HISTORY. — Introduction  of  Egyptian  Civilization  into  Europe. — 
The  Registry  of  Facts  by  Writing. — Egyptian  Philosophy  in  the  Greek  Schools. —  The  Persian 
Empire :  its  Influence. — Analytical  Quality  of  the  European  Mind. — Influence  of  the  Greek 
Schools  on  modern  Philosophy. 

Origin  of  European  Commerce. — Discovery  of  the  Straits  of  Gibraltar. — Macedonian  Campaign. 
— Reconstruction  of  Monarchy  in  Egypt. 

The  Roman  Empire:  its  centralizing  and  civilizing  Power. — Fall  of  European  Paganism. — In- 
fluence of  the  Christian  Church. — The  Sabbath  Day. —  The  Reformation. 

Influence  of  Mohammedanism  on  Europe. —  The  Arab  physical  Science. —  TJie  Crusades. — Dis- 
covery of  America  by  the  Spaniards. — Fall  of  the  Spanish  Power. 

Later  Mental  Changes  in  Europe.— Disappearance  of  Credulity.— Physiological  Change  of  Eu- 
ropeans.— Effect  of  Mohammedanism  in  changing  the  Centre  of  Intellect  of  Europe. — Analyt- 
ical Tendency  of  the  European  Mind. — Advantages  resulting  therefrom. 

HAVING  described  man  as  an  individual,  we  have  next  to  consider  him 

Dependency  of  *n  m's  soc^  relations ;  for  so  closely  are  his  actions  connect- 

sociai  career  on  ed  with  his  organization,  that  it  may  be  said  that  universal 

history  is  only  a  chapter  of  physiology.    It  is  acknowledged, 


COMPARATIVE   SOCIOLOGY.  603 

even  by  those  who  have  given  but  a  superficial  attention  to  the  subject, 
that  there  is  a  connection  between  corporeal  development  and  historical 
career ;  that  those  races  who  have  led  the  way  in  the  course  of  civiliza- 
tion, and  those  who  still  remain  in  the  savage  state,  are  characterized  by 
striking  anatomical  peculiarities,  particularly  in  the  size  and  development 
of  their  cerebral  hemispheres.  Such  general  conclusions  are  strengthened 
by  our  observations  on  the  animal  series,  the  lower  members  of  which 
offer  together  a  sameness  of  structure  and  an  identity  in  their  course  of 
life.  In  those  the  metamorphoses  of  which  have  been  stud-  Structure  and 
led,  it  is  always  noticed  that  every  change  of  structure  is  at  habit  in  the 
once/ollowed  by  a  change  of  habit,  yet,  during  the  continuance  case  of  msects- 
of  a  given  condition,  their  manner  of  life  is  without  any  variation.  The 
actions  of  one  insect  are  for  the  most  part  the  actions  of  another  of  the 
same  kind  and  in  the  same  state,  whether  larva,  pupa,  or  imago.  But 
in  the  midst  of  all  this  automatism  there  are,  however,  the  glimmerings 
of  a  free  will.  The  animal  world  presents  forcible  illustrations  on  every 
hand  on  the  connection  of  structure  and  habit. 

Philosophical  views  of  human  sociology  are  only  to  be  attained  by 
treating  that  great  problem  in  the  same  manner  that  we  have  comparative 
learned  to  treat  so  many  others  in  physiology.  We  must  in-  sociology. 
elude  in  our  discussion  all  other  animal  races,  and  not  close  our  eyes  to 
the  fact  that  there  is  such  a  thing  as  comparative  sociology.  We  ob- 
serve the  republican  propensities  of  the  ant,  the  monarchical  life  of  bees, 
the  solitary  habit  of  other  tribes.  Is  it  not,  at  least  in  part,  because  of 
cerebral  peculiarities  that  one  kind  of  bird  is  polygamous,  and  another 
observes  an  annual  or  perpetual  monogamy ;  that  the  buffalo  delights  in 
the  society  of  his  kind,  but  the  lion  will  tolerate  no  neighbor ;  that  the 
horse  runs  in  herds,  and  adopts  an  organized  system,  submitting  to  a  cap- 
tain whose  motions  he  follows  ?  We  can  not  suppose  that  these  habits 
are  the  sole  result  of  a  present  and  immediately  active  external  influence 
which  calls  them  forth ;  an  internal  influence  is  also  at  work,  an  internal 
influence  dependent  on  organization. 

A  discussion  of  the  problem  of  human  sociology  could,  therefore,  only 
be  completed  after  a  study  of  the  same  problem  in  the  entire  animal  se- 
ries—  a  task  requiring  varied  and  profound  knowledge  of  natural  his- 
tory and  comparative  anatomy.  Indeed,  the  present  state  of  these  sci- 
ences does  not  enable  us  to  accomplish  it.  The  remarks  I  am  about  to 
make  are,  therefore,  of  a  very  imperfect  kind.  The  social  problems  pre- 
sented to  us  by  animals  are  a  fitting  introduction  to  the  social  problems 
of  man. 

For  the  clearer  understanding  of  what  follows,  it  may  Distinction  be_ 
therefore  be  observed  that  we  may  receive  the  term  instinct  tween  instinct 
as  indicating  a  faculty  incapable  of  improvement,  and  possess- 


604  COMPARATIVE   SOCIOLOGY. 

ed  by  each  individual  exhibiting  it  spontaneously,  without  experience 
or  imitation.  The  suggestions  of  instinct  are  often  instantaneous  and 
always  unvarying ;  those  of  reason  involve  deliberation,  and  into  them 
the  element  of  time  enters.  They  also  involve  error.  Animals  which, 
for  a  thousand  years,  nay,  indeed,  through  all  time,  have  never  invented, 
never  improved,  never  varied,  all  of  the  same  kind  being  equally  skill- 
ful, are  to  be  considered  as  actuated  by  instinct,  not  by  reason.  Those 
of  which  it  may  be  said  that  they  perceive,  remember,  think,  compare, 
and  then  form  a  judgment,  are  to  be  considered  as  possessing  reason,  and 
this  the  more  as  they  the  more  perfectly  accomplish  that  end.  In  this 
respect,  man  is  approached  by  the  quadrumana,  the  elephant,  the. dog, 
but  the  immense  interval  which  separates  him  from  them  is  at  once  in- 
dicated by  the  fact  that  they  appreciate  only  good  and  evil,  so  far  as  in- 
volved in  pleasure  and  pain ;  but  he  contemplates  equally  the  good,  the 
beautiful,  and  the  true. 

The  historian  may  perhaps  view  with  resentment  an  attempt  on  the 
Connection  of  Part  °^  Pnysi°l°gists  *°  accomplish  the  annexation  of  the  ter- 
history  and  ritory  in  which  he  labors.  With  difficulty  will  he  be  brought 
physiology.  ^o  ajm't  fae  dogma  that  the  history  of  men  and  of  nations 
is  only  a  chapter  of  physiology.  He  doubtless  will  smile  at  the  absurd- 
ities of  a  doctrine  which  places  under  a  common  point  of  view  the  doings 
of  caterpillars,  ants,  and  wasps,  with  the  high  resolves  of  senates  and 
emperors — which  undertakes  to  consider  how,  out  of  the  most  obscure, 
the  most  august  may  proceed. 

But  it  is  none  the  less  true  that  there  exists  a  comparative  sociology, 
as  well  as  a  comparative  anatomy  and  a  comparative  physiology.  Struc- 
ture, function,  and  career  are  all  inseparably  connected. 

When  we  were  considering,  in  a  former  chapter,  the  nervous  mechan- 
ism of  insects,  we  saw  how  that,  from  the  purely  automatic,  the  volun- 
tary is  gradually  produced  by  the  development  on  the  ventral  cord  of  an 
apparatus  for  the  registry  of  impressions,  the  cephalic  ganglia.  These 
registered  impressions  are  the  cause  of  the  most  surprising  psychical  re- 
sults. 

The  action  of  barbarian  communities  is  as  purely  automatic  as  the  ac- 
Barbarism  and  tion  of  an  insect,  which  never  had,  or  from  which  there  have 
civilization.  keen  removed,  the  registering  ganglia.  Irritate  the  decap- 
itated wasp,  it  will  sting.  The  uninjured  wasp  has  a  choice  of  action ; 
it  may  possibly  fly  away.  The  action  of  civilized  communities  is  of  a 
far  higher  kind :  they  are  guided  in  what  they  do  by  experience.  In  the 
progress  of  civilization  there  have  arisen  the  means  of  permanently  re- 
cording past  events.  Such  records  influence  us  in  deciding  how  we  shall 
act.  They  constitute  knowledge. 

If  we  may  compare  small  things  with  great,  is  there  not  an  analogy 


INSECT   SOCIETY.  605 

between  the  manner  in  which  the  registering  mechanism  of  Analogy  be- 


an insect  or  other  animal  is  evolved,  and  the  manner  in  tween  i 
which  the  means  of  perpetuating  and  disseminating  a  knowl-  ment  and  social 
edge  of  events  have  arisen  in  human  society  ?     The  one,  it  is  career- 
true,  appertains  to  individual  life  ;  but  is  there  any  fact  more  clearly 
made  manifest  by  physiology  than  that  of  the  parallelism  of  race  life  and 
individual  life,  no  matter  how  lowly  that  individual  life  may  be? 

An  insect  presents  us  with  surprising  actions,  because  it  possesses 
within  itself  the  means  of  registering  the  events  which  occur  in  its  little 
circle.  Nations  act  wisely  and  well,  according  as  they  are  guided  by 
their  store  of  experience. 

If  our  pride  can  be  so  far  overcome  as  to  admit  that  in  the  history  of 
the  life,  even  of  an  insect,  the  progress  of  mankind  is  shadowed  forth, 
that  is  to  say,  universal  history  is  seen  in  a  microscopic  manner,  it  will 
not  be  too  much  to  hope  that  we  shall  then  entertain  physical  or  mechan- 
ical ideas  of  the  social  career,  that  society  advances  in  a  definite  way,  has 
its  laws  of  equilibrium  and  movement,  its  centre  of  intelligence,  its  centre 
of  power,  in  short  its  statics  and  dynamics. 

Though  it  is  only  one  out  of  many  instances  that  might  be  presented, 
let  us  briefly  consider  social  life  in  the  inferior  tribe  to  which  reference 
has  been  made  ;  let  us  also  look  at  some  of  the  individual  peculiarities 
of  insects.  Our  sentiments  of  exclusiveness  and  pride  may  be  corrected 
thereby. 

Insects  form  societies  for  mutual  assistance,  defense,  invasion,  emigra- 
tion, mere  pleasure  —  societies  which  undoubtedly  arise  in 

.  /.  •  T          1  T   /.  •  s^<*  ,1  Insect  society. 

the  experience  ot  passions,  such  as  love  and  tear.  Ut  these 
the  duration  is  variable  ;  some  last  through  the  larva  state  only,  some  are 
confined  to  the  imago,  some  are  maintained  through  life.  The  organiza- 
tion by  which  their  object  is  accomplished  is  various,  monarchical,  re- 
publican. The  caterpillars  of  the  processionary  moths  are  guided  in 
their  march  by  a  leader  ;  the  termites  obey  at  once  a  king  and  a  queen. 
The  lust  of  power  is  not  alone  felt  among  human  monarchs  ;  the  queen 
bee  never  rests  till  she  lias  assassinated  her  rival.  All  insects  of  the 
same  kind  are  not  born  equal,  nor  do  all  pursue  the  same  occupation  ; 
some  follow  a  life  of  leisure,  some  devote  themselves  to  the  profession  of 
arms,  some  are  laborers.  When  the  metropolis  of  the  termites  is  attack- 
ed, the  laborers,  as  non-combatants,  retire,  but  the  soldiers  come  out. 
The  ants,  with  which  wre  are  more  familiar,  engage  in  military  and  filli- 
bustering  expeditions  ;  they  make  reconnoissances,  set  sentinels,  march  in 
a  definite  order,  the  van  alternately  falling  to  the  rear  ;  their  lines  of  com- 
munication are  maintained,  and,  if  necessary,  swift  couriers  are  disp&tch- 
ed  for  re-enforcements.  If  successful,  they  not  only  carry  off  the  ene- 
mies' stores,  but  reduce  the  vanquished  to  actual  servitude,  compelling 


606  HABITS   OF   INSECTS. 

them  to  work  as  slaves.  They  have  notions  of  property,  and,  though 
some  of  them  practice  cannibalism,  they  will  amuse  themselves  in  more 
pleasant  occupations,  tumbling  and  playing  together  like  kittens  or  pup- 
Habits  of  pies-  With  a  sentiment  of  strict  justice,  the  wasp  who  has  re- 
insects,  turned  from  a  successful  foray  divides  his  booty  among  the 
males,  females,  and  the  laborers  who  have  been  working  in  the  vespiary ; 
nor  is  the  sentinel,  who  is  doing  duty  at  the  door,  forgotten.  If,  through 
the  chances  of  war  or  by  accident,  any  one  has  sustained  a  grave  injury, 
in  some  tribes  the  most  devoted  sympathy  is  shown :  the  ant  will  carry 
his  wounded  friend  out  of  the  hot  of  the  fight ;  in  other  tribes  a  more 
than  Roman  firmness  is  displayed :  the  sufferer  is  put  out  of  pain  by  his 
companion.  Expecting  an  attack,  some  insects  will  shut  their  doors  at 
night,  and  barricade  them  within,  or,  if  the  danger  is  continual,  will  build 
masked  gateways  in  succession,  with  interior  walls  that  command  them. 
They  are  no  contemptible  engineers.  They  can  construct  and  maintain 
roads  of  great  length,  with  paths  branching  from  them,  which,  if  neces- 
sary, they  keep  mown.  They  cross  streams  by  throwing  themselves 
into  floating  bridges,  and  the  damage  done  to  their  premises  by  an  in- 
vader they  show  the  most  singular  skill  and  alacrity  in  repairing.  How 
many  are  the  contrivances  to  which  insects  resort  to  carry  out  their  pur- 
poses !  The  caterpillar  of  the  cabbage  butterfly  makes  a  ladder  and  goes 
up  it ;  the  geometrical  caterpillar  lets  down  a  rope,  and,  for  fear  of  hurt- 
ing himself,  drops  a  foot  at  a  time.  The  gossamer  spider  sends  forth  a 
thread  fine  enough  to  act  like  a  balloon,  and,  floating  in  the  air,  he  de- 
scends or  rises  by  winding  it  up  or  letting  it  out.  There  are  other  in- 
sects which  make  diving-bells,  and  go  under  the  water.  No  bird  makes 
a  net,  no  beast  a  pitfall :  men  and  insects  do  both.  A  gang  of  sailors 
will  carry  a  spar  by  supporting  it  on  alternate  sides  on  their  shoulders ; 
a  gang  of  ants  will,  in  like  manner,  carry  a  straw  or  a  long  worm.  There 
are  spiders  which  show  as  much  dexterity  as  an  Indian  in  sneaking  for- 
ward to  get  in  reach  of  their  prey. 

In  their  domestic  economy,  how  wonderful !  Some  build  their  houses 
of  artificial  stone,  some  of  pasteboard  which  they  make.  Some  cover 
their  rooms  with  tapestry,  some  lay  carpets  of  silk  on  the  floor,  some 
hang  their  doors  on  silk  hinges,  so  that  they  shut  by  their  own  weight. 
They  make  arches,  domes, 'colonnades,  stair-cases.  They  practice  con- 
cealment of  food.  Ray,  an  accurate  observer  and  a  very  pious  man,  says 
of  a  sand-wasp  that  it  carried  a  caterpillar  fifteen  feet,  removed  a  pellet 
that  closed  the  mouth  of  a  hole,  deposited  its  booty  therein,  came  out, 
and  rolled  the  pellet  back  on  the  hole,  scratched  dust  thereon  like  a  dog, 
went  for  rosin  to  agglutinate  it,  leveled  the  ground,  and  put  two  pine 
leaves  to  mark  the  place.  However  much  we  may  smile  at  this  anec- 
dote, it  may  satisfy  us  of  the  high  opinion  entertained  of  the  accom- 


THE   CEPHALIC   GANGLIA. 


607 


plishments  of  insects  by  those  who  have  been  close  observers  of  their 
habits. 

Dr.  Laycock  remarks,  when  speaking  of  the  cephalic  ganglia  of  insects 
(Med.  Chir.  Rev.,  July,  1853) :  "  On  what  structures  de-  instincts  of  in- 
pend,  if  not  on  these  cephalic  ganglia,  all  those  wonderful  Jj^?  ^hanc" 
instincts  which  mimic  in  their  operation  the  arts  of  man?  ganglia. 
There  is  hardly  a  mechanical  pursuit  in  which  insects  do  not  excel.  They 
are  excellent  weavers,  house-builders,  architects.  They  make  diving- 
bells,  bore  galleries,  raise  vaults,  construct  bridges.  They  line  their 
houses  with  tapestry,  clean  them,  ventilate  them,  and  close  them  with 
admirably-fitted  swing-doors.  They  build  and  store  warehouses,  con- 
struct traps  in  the  greatest  variety,  hunt  skillfully,  rob,  and  plunder. 
They  poison,  sabre,  and  stab  their  enemies.  They  have  social  laws,  a 
common  language,  divisions  of  labor,  and  gradations  of  rank.  They 
maintain  armies,  go  to  war,  send  out  scouts,  appoint  sentinels,  carry  off 
prisoners,  keep  slaves,  and  tend  domestic  animals.  In  short,  they  are 
mentally  a  miniature  copy  of  man." 

The  surprising  character  of  some  of  these  facts  might  disappear  were 
we  acquainted  with  what  may  be  termed  the  spring  of  the  action.  It 
has  been  said  by  Dr.  Whateley  that  the  building  of  a  comb  is  like  the 
provisioning  of  a  city,  in  which,  through  the  desire  of  the  dealers  to  get 
wealth,  is  solved  what  is  probably  the  most  intricate  of  social  problems. 
It  is  done  by  no  design  of  theirs,  and  yet  they  advance  to  it  as  if  im- 
pelled by  gravitation  or  some  other  insuperable  force.  A  printer  may 
put  types  together  to  get  money  without  ever  troubling  himself  about 
the  diffusion  of  knowledge.  A  bee  may  find  gratification  in  what  he  is 
doing  without  any  concern  about  the  final  use  of  the  comb. 
Of  the  cephalic  ganglia  spoken  of  in  the  preceding  paragraphs,  Fig. 
295  is  an  illustration  from  Mr.  Newport,  in  the  case  of 
the  imago  of  the  Sphinx  ligustri :  <z,  cephalic  ganglia ;  £, 
£,  eyes  ;  <?,  anterior  median  ganglia ;  d,  d,  posterior  lat- 
eral ganglia  of  the  stomato-gastric  system ;  Nervous  system 
e,f,  large  ganglionic  masses  in  the  thorax,  °f  insects, 
giving  nerves  to  the  legs  and  wings.  It  is  Fig.  296. 
to  be  understood  that  upon  these  ganglia 
the  voluntary  action  of  insects  depends. 
They  are  the  places  of  reception  of  the  im- 
pressions on  the  organs  of  special  sense  and 
cephalic  ganglia,  the  seat  of  memory.  The  automatic  or  in- 
voluntary apparatus  is  in  part  seen  at  Fig.  296,  which  is  the 
thoracic  portion  of  the  nervous  system  of  the  pupa  of  the  same 
insect :  <z,  #,  c,  three  ganglia  of  the  ventral  cord ;  d,  d,  their 

Thoracic  portion 

connecting  trunks;  e,  £,  respiratory  ganglia.      The  entire  of  ventral  C0rd. 


Fig.  295. 


608  MEMOEY  OF  INSECTS. 

nervous  mechanism  for  the  larva  state  has  been  shown  in  Fig.  126 ;  for 
the  pupa,  127 ;  for  the  imago,  128 ;  from  which  it  will  be  recognized 
that  the  nervous  system  of  insects,  as  they  pass  through  their  metamor- 
Changes  in  the  phoses,  undergoes  change.  In  the  larva  state,  the  nerves,  as 
nervous  system  they  branch  forth  from  the  ventral  cord,  indicate  by  their  uni- 
mTtTmorp^o-  formity  the  equality  of  the  segments  of  the  body.  In  many 
sis-  cases  the  cord  is  separated  throughout  its  whole  length  into 

its  two  constituent  strands,  and  the  cephalic  ganglia  are  minute  because 
of  the  imperfect  condition  of  the  organs  of  sense.  In  the  .pupa  state 
there  is  a  general  approach  of  the  ventral  ganglia,  an  increase  of  the 
cephalic,  and  a  thickening  of  the  strands  which  connect  that  organ  with 
the  suboesophageal.  In  the  imago  state  the  cephalic  ganglia  have  still 
farther  increased  to  a  size  which  corresponds  to  the  great  development 
of  the  organs  of  sense ;  the  ventral  ganglia  appear  to  have  coalesced  in 
the  thorax.  The  general  result  of  these  changes  during  metamorphosis 
is  therefore  to  effect  a  concentration  of  the  nervous  centres  in  the  head 
and  in  the  thorax,  the  ganglia  of  special  sensation  coalescing  in  the  for- 
mer, and  those  of  motion  in  the  latter  region.  We  may  remark  that 
these  modifications  strikingly  illustrate  the  observation  that  change  in 
habits  of  life  is  always  preceded  by  change  of  the  nervous  system. 

Besides  being  the  repository  of  the  impressions  of  the  special  senses, 
Seat  of  mem-  tne  cephalic  ganglia  discharge  a  function  of  a  more  general 
ory  in  insects.  anc[  most  important  kind,  since  doubtless  they  are  the  seat  of 
memory.  That  insects  of  the  more  elevated  kind  have  the  power  of 
recollection  there  can  not  be  any  doubt.  If  there  were  no  other  fact, 
their  recognition  of  their  homes  would  be  sufficient  to  establish  this.  A 
thousand  trivial  incidents  offer  indirect,  but  instructive  and  interesting 
proofs  of  the  same  thing.  When  a  spider  who  has  been  disturbed  feigns 
death  in  order  to  avoid  the  cause  of  his  alarm,  he  proves  his  capacity  of 
recollection,  as  also  when  he  has  been  brought  out  from  his  concealment 
by  touching  his  web,  and,  discovering  the  nature  of  the  imposition  that 
has  been  practiced  upon  him,  refuses  to  come  forth  upon  a  repetition  of 
the  trial.  The  quality  which  the  cephalic  ganglia  thus  possess  of  bear- 
ing upon  themselves  the  enduring  traces  of  impressions  received  through 
the  sensory  organs  scarcely  requires  here  to  be  more  particularly  exam- 
ined. In  the  preceding  book,  in  the  chapter  on  inverse  vision,  various 
facts  have  been  mentioned  which  illustrate  the  faculty  possessed  by  the 
optic  centres  in  man  of  retaining  visual  impressions  for  a  considerable 
period  of  time ;  as,  for  instance,  if,  when  we  awake  in  the  morning,  our 
eyes  are  directed  to  the  bright  window  and  then  closed,  a  representation 
thereof  will  still  continue  to  be  seen  in  its  natural  colors  and  relations,  a 
representation  which  gradually  fades  away;  and,  in  like  manner,  the 
cephalic  ganglia  register  the  impressions  they  receive  from  the  optic, 


DESCARTES'S   DOCTRINE.  609 

the  auditory,  olfactive,  and  other  nerves  that  pass  to  them,  The  ce  halLc 
and  preserve  the  vestiges  thereof;  for,  if  this  be  not  the  case,  ganglia  are 
it  is  wholly  impossible  to  explain  how  insects  should  have  the  W8^ef8f 
power  of  remembering,  even  though  it  be  indistinctly  or  imperfectly, 
things  that  are  past :  those  things  or  effects  must  have  left  upon  them 
an  enduring  mark. 

The  ganglia  of  the  ventral  cord,  with  their  related  nerve  trunks,  con- 
stitute a  series  of  automatic  nerve  arcs,  their  immediate  ob-  ...  - .. 

'  f  Action  oi  the 

ject  being  locomotion.  As  has  been  said,  the  impression  of  ventral  cord 
the  surface  upon  which  the  insect  rests  gives  rise,  under  or-  a 
dinary  circumstances,  to  muscular  contraction,  and  thereby  motion,  and 
the  same  thing  occurs  under  circumstances  of  unusual  experimental  dis- 
turbance, as  when  irritation  of  any  kind — for  instance,  the  pungent  va- 
por of  ammonia — is  applied  to  one  side  of  a  centipede,  the  body  is  flex- 
ed in  such  a  way  as  to  get  rid,  as  far  as  possible,  of  the  noxious  fume. 
These  movements  are  purely  reflex,  and  in  their  production  the  cephalic 
ganglia  are  in  no  manner  concerned. 

Guiding  and  controlling  these  purely  reflex  operations,  the  cephalic 
ganglia,  by  means  of  the  fibres  which  they  send  in -company  Controlling 
with  the  trunks  of  the  ventral  cord,  can  exert  their  influence  actl°n  of  the 

cephalic  gan- 

in  the  remotest  part  of  the  body.     That  influence  we  distin-  glia. 
guish  as  being  of  a  twofold  nature :  in  part  it  is  due  to  impressions 
which  are  being  at  that  moment  received  through  the  various  organs  of 
sense — the  eye,  the  ear,  or  whatever  other  such  organ  the  insect  under 
consideration  may  possess,  and  in  part  arising  from  the  residues  of  old 
impressions  which  the  ganglion  has  formerly  received.     It  does  not 
therefore  seem  possible,  at  least  as  regards  the  more  perfect  of  these 
tribes,  to  accept  the  views  of  Descartes,  who  regarded  all  insects  as  mere 
automata.     They  are  automata  only  so  far  as  the  action  of  Descartes's 
their  ventral  cord  and  that  portion  of  their  cephalic  ganglia  ^jg  Vrctu- 
which  deals  with  contemporaneous  impressions  is  concerned,  tomata. 
but  they  are  not  automata,  since  they  are  under  the  influence  of  those 
ganglia  as  the  registers  of  past  impressions. 

What  has  been  said  respecting  insects  applies  to  all  higher  tribes  of 
life.  Man  himself  is  no  exception.  In  the  preceding  book  we  have  shown 
that,  so  far  as  his  spinal  nervous  system  is  concerned,  he  is  simply  an 
automaton,  and  that  it  is  the  development  of  a  brain  thereupon  which 
makes  him  capable  of  voluntary  action.  We  have  seen  that  in  his  indi- 
vidual progress  part  is  evolved  from  part,  an  ever-increasing  complexity 
and  an  ever-continuing  improvement.  Cerebral  mech 

It  is  the  same,  also,  with  the  group  to  which  he  belongs —  anism  in  ani- 
the  vertebrates.     Just  in  proportion  to  the  advance  of  their 
cerebral  mechanism  are  their  psychical  powers.    The  amphi-  powers. 

QQ 


WRITING*  AS  A  RECORD. 

oxus,  which  has  no  cerebral  hemispheres,  represents  the  condition  of  man 
when  the  action  of  his  brain  is  suspended  in  sleep ;  the  fish,  the  reptile, 
the  bird,  follow  in  an  ascending  order — an  order  which  man  himself  passes 
through  in  his  individual  progress  of  development. 

And  man  in  the  aggregate — in  society — in  the  race — does  the  same,  his 

historical  career  being  a  transcript  of  his  individual  career.     Generation 

after  generation  leads  a  purely  automatic  life,  the  life  of  barbarism ;  but, 

by  degrees,  there  is  evolved  in  such  conditions  the  means  of  registry  or 

record.    The  acts  and  thoughts  of  one  age  can  then  be  trans- 

Writing  is  the     '  ° .  .  c 

means  of  record  mitted  to  another,  and  can  influence  its  acts  and  thoughts. 
Civilization  can  not  exist  without  writing,  or  the  means  of 
record  in  some  shape. 

Writing  once  invented,  the  advance  in  society  is  again  precisely  as  it 
is  in  the  individual.  In  part  it  is  regulated  by  the  physical  circum- 
stances around,  in  part  by  the  interior — the  acquired  principle. 

In  the  superficial  sketch  which  I  intend  now  to  give  of  the  progress 
of  European  civilization,  there  are  certain  facts  which,  from  their  promi- 
nence, can  not  fail  to  arrest  our  attention.  They  are, 

1.  Europe  remained  in  the  barbarous  state  until  it  obtained  the  means 
General  facts  °^  PerPetua^nS  i^eas? tnat  ig  *°  Sa7>  until  it  learned  the  art  of 

of  European      writing. 

2.  The  progress  of  civilization  in  Europe  was  attended  by 
an  absolute  physiological  change  in  its  inhabitants.  They  were  brought 
nearer  to  the  condition  of  the  inhabitants  of  a  more  temperate  climate. 
On  this  point,  however,  we  have  dwelt  to  a  sufficient  extent  in  the  pre- 
ceding chapter. 

3.  The  European  mind  is  analytic,  that  of  Asia  is  synthetic.  In  Eu- 
rope, the  action  in  philosophy,  in  religion,  in  politics,  tends  to  the  inces- 
sant decomposition  of  a  thing  into  its  parts,  and  their  separate  discus- 
sion. The  results  of  this  tendency  are  seen  in  many  of  the  practical  social 
difficulties  of  modern  times. 

Before  entering  on  this,  the  conclusion  of  his  work,  the  author  may 
recall  by  a  few  passing  remarks  the  general  views  which  have  been  in- 
cidentally scattered  through  preceding  pages  respecting  the  nature  of 
man,  the  influence  of  surrounding  circumstances  over  him,  his  social  posi- 
tion, the  definiteness  of  his  career,  a  definiteness  which  authorizes  us  to 
treat  his  history,  not  as  though  it  were  composed  of  chance  events,  but 
as  a  fitting  subject  for  the  contemplation  of  physiology. 

Man  is  every  where  constructed  upon  the  same  essential  type,  and 
hence,  in  one  sense,  he  acts  in  an  invariable  manner,  but  that  type  passes 
forward  in  development  to  many  different  aspects,  and  hence,  in  another 
sense,  he  exhibits  differences  in  his  determinations  and  movements. 

With  the  form  and  size  of  the  brain,  the  intellectual  capacity  of  man 


NATURE  OF  MAN.  611 

varies.  In  a  state  of  nature,  his  mental  powers  are  in  close  relation  with 
the  climate  in  which  he  lives,  attaining  their  greatest  perfection  in  the 
wanner  portion  of  the  temperate  zone ;  but  under  the  artificial  condition 
of  civilization,  in  which  the  vicissitudes  of  the  seasons  are  compensated 
for  by  food,  fire,  shelter,  and  clothing,  properly  adjusted,  he  gains  his 
maximum  development  in  a  somewhat  higher  latitude. 

After  what  has  been  said  in  the  last  chapter  respecting  the  influence 
of  physical  circumstances  on  the  structure  of  man,  producing  modified 
development  in  our  typical  form,  and  thereby  giving  rise  to  many  dis- 
tinct families,  it  will  be  anticipated  that  those  circumstances  must  con- 
sequently modify  our  mental  operations,  our  manner  of  thinking  and  act- 
ing, that  is  to  say,  must  leave  their  marks  on  our  history  as  nations. 
For  a  long  time  this  has  been  recognized  in  a  general  manner :  the  mount- 
aineer thinks  differently  and  acts  differently  to  the  native  of  the  low- 
lands ;  he  whose  life  is  spent  on  the  borders  of  the  sea  to  him  who  lives 
in  the  great  plains  in  the  interior  of  continents.  But  it  is  not  to  these 
influences  as  operating  by  association  on  the  individual  that  I  now  refer ; 
it  is  rather  to  the  profound  effect  they  have  had  in  producing  a  special 
cerebral,  and,  therefore,  mental  organization  in  the  course  of  many  gen- 
erations on  races  and  nations. 

Let  us  always  remember  that  there  is  a  common  principle  which  un- 
derlies the  varied  movements  and  determinations  of  men  every  where — a 
principle  from  which  no  one  can  disentangle  himself.  At  the  bottom  of 
even  the  most  diverse  actions  it  may  be  discerned,  just  as  we  can  detect 
the  fundamental  type  of  our  organization  under  the  most  varied  forms. 

As  from  the  physical  point  of  view  there  is  a  standard  man  who,  in 
weight,  height,  strength,  and  other  such  like  particulars,  rep-  „ 

,    5  ,r     Nature  of  man. 

resents  the  entire  human  family,  so,  in  an  intellectual  point 
of  view,  there  is  a  standard  man  who,  in  mental  progress,  manner  of 
thinking  and  of  acting,  represents  the  whole  race.  There  are  also  sub- 
ordinate standards,  the  representatives  of  particular  groups  or  nations. 
It  is  to  these  standards  that  we  are  continually  appealing  in  arriving  at 
a  judgment  of  the  acts  of  individuals.  The  special  history  of  these 
phases  constitutes,  in  a  philosophical  sense,  national  history.  The  rec- 
ord of  the  development  of  the  fundamental  type  constitutes  universal 
history. 

I  have  already  remarked  that  universal  history  is  only  a  chapter  in 
physiology.  Since,  by  reason  of  the  similarity  of  construction  of  the 
cerebral  apparatus,  the  actions  of  men  will  present  a  uniformity  when 
under  the  influence  of  similar  motives  or  impulses,  there  is  not  only  a 
resemblance  between  such  actions  among  different  persons,  influence  of 
but  also  it  may  be  discerned  when  nation  is  compared  with 
nation,  and  race  with  race ;  for  the  movements  of  communi-  on  him. 


612  CAREER   OF   MAN. 

ties  depend  on  the  same  motives  as  the  movements  of  individuals,  being 
indeed  the  sum  of  individual  determinations.  But  when  multitudes  and 
masses  are  thus  brought  under  our  consideration,  the  element  of  free-will 
seems  for  the  most  part  to  disappear,  and  events  assume  an  air  of  pre- 
destination. To  this  principle  it  is  that  history  owes  its  chief  value,  and 
truly  becomes,  as  is  often  said,  philosophy  teaching  by  example.  The 
intelligent  man  who  lived  twenty  centuries  ago  would  doubtless  have 
come  to  the  same  decision  which  is  reached  by  the  intelligent  man  of  our 
times ;  the  same  propositions  being  submitted  to  both,  both  guiding 
themselves  by  similar  principles  to  a  like  result.  The  logic  of  truth  is 
eternal,  for  it  is  the  expression  of  the  manner  of  action  of  our  cerebral  ap- 
paratus, the  type  of  which  never  changes ;  and  since  there  is  thus  no 
essential  change  in  the  typical  construction  of  man,  and  therefore  none 
in  the  manner  of  operation  of  his  mental  processes,  since  physical  nature 
Definiteness  of  ig  unvarying,  and  the  events  of  life  spring  one  out  of  another 
his  career.  jn  a  regular  order  or  sequence,  there  must  arise  those  same 
analogies  in  the  history  of  race  compared  with  race,  and  nation  compared 
with  nation,  that  are  so  obvious  when  individual  is  compared  with  indi- 
vidual. Of  every  great  future  event  there  is  therefore  a  past  history,  for 
every  such  event  has  had  its  precedent  in  other  histories,  and  therefore 
its  prognostic.  Things  will  follow  in  a  definite  order  so  long  as  the  in- 
fluences of  external  nature  are  the  same,  and  so  long  as  the  construction 
of  the  human  brain  is  the  same. 

The  political  foresight  of  the  most  eminent  statesmen  depends  on  a 
gift  of  appreciating  national  mental  types,  like  that  possessed  by  great 
sculptors  or  painters  of  appreciating  a  standard  of  beauty.  It  is  this 
which  enables  them  to  foresee  the  probable  consequences  of  events,  and 
to  realize  the  expected  action  of  individuals,  and  even  of  masses  of 
men.  In  such  actions  there  is  far  more  uniformity  than  is  commonly 
supposed.  The  same  general  conditions  which  yield  to  the  post-office 
a  definite  percentage  of  misdirected  letters  every  year — which,  with  mar- 
velous fidelity,  give  to  the  hospitals,  the  jails,  the  bills  of  mortality,  their 
expected  numbers,  operate  from  age  to  age,  and  in  one  nation  as  in  an- 
other, and  hence  arises  that  appearance  of  fate  in  the  action  of  masses 
to  which  we  have  alluded;  hence  also  it  is  that  the  same  cycle  of 
events  re-occurs  again  and  again,  diversified,  perhaps,  but  never  essen- 
tially changed  by  the  influence  of  individual  free-will.  As  the  compar- 
ative anatomist  exhibits,  in  the  different  members  of  the  living  series, 
their  common  points  of  resemblance — that  this  organ  in  one  animal  is 
the  homologue  of  that  in  another,  and  this  function  the  analogue  of  that, 
so  the  philosophical  statesman,  acknowledging  the  essential  principle  of 
comparative  history,  reasons  from  nation  to  nation  and  from  age  to  age. 


PRIMITIVE   STATE   OF   EUROPE.  013 

CHIEF   EVENTS   IN  THE   CIVILIZATION   OF   EUROPE. 

The  Odyssey  presents  us  a  vivid  picture  of  the  state  of  Europe  a 
thousand  years  before  the  birth  of  Christ.  A  twilight  was  Euro  e  emer  _ 
breaking  on  the  most  eastern  verge  in  the  countries  adjoin-  ing  from  bar- 
ing the  Hellespont,  but  the  West  and  the  North  were  im-  b 
mersed  in  a  night  of  barbarism.  The  unfolding  mind  is  ever  prone  to 
fill  darkness  with  imaginary  creations,  and  it  was  with  the  white  race  at 
that  period  as  it  is  with  a  child.  Every  shore  of  the  Mediterranean 
and  Black  Seas  was  full  of  prodigies.  To  the  Greek  no  fiction  was  too 
marvelous  for  belief  if-  it  was  separated  from  his  view  by  a  hundred 
years  or  a  hundred  miles,  the  exaggeration  of  tradition  confirming  it  in 
the  one  case,  and  the  difficulties  of  travel  in  the  other.  His  horizon  was 
crowded  with  enchantresses  like  Circe,  sorcerers  like  Tiresias,  monsters 
like  the  Cyclops.  Gods  and  goddesses  were  perpetually  flying  through 
the  air  ;  every  hill  had  its  supernatural  legend,  every  forest  its  phantom. 
Even  the  mouth  of  hell  was  on  the  farther  side  of  the  Euxine. 

A  religion  of  superstition  is  very  liable  to  be  connected  with  a  life 
of  evil  works.  The  maritime  enterprise  of  those  days  seems  to  have  re- 
ceived no  little  incitement  from  the  temptations  of  piracy  —  a  profession 
to  which,  even  at  a  later  period,  the  Greek  appears  instinctively  to  turn ; 
nor  were  these  felonious  expeditions  restricted  to  the  taking  of  goods ;  they 
drew  an  additional  profit  from  the  stealing  of  men.  The  evidences  of 
even  a  still  darker  crime  may  also  be  discerned,  since  there  were  people 
accused  by  common  fame  of  eating  the  captives  who  fell  into  their  hands. 
The  white  man,  therefore,  emerges  from  his  state  of  barbarism  a  pirate, 
a  slaver,  a  cannibal,  cruel  in  his  moment  of  power,  and  debased  by  an 
incredible  superstition  in  his  moment  of  fear. 

Unable  to  originate  his  civilization  for  himself,  he  drew  the  elements 
of  it  from  another  country.     By  the  concurring  testimony  of  Civilizatio 
all  authors,  as  well  as  the  internal  evidences  of  ancient  history,  originated 
that  great  blessing  is  the  gift  of  Egypt.     For  thirty-four  cen-  X1 
turies  before  our  era  that  country  was  governed  by  dynasties  of  kings, 
succeeding  each  other  without  interruption.     Its  soil,  proverbially  fer- 
tile, sustained  a  population,  estimated,  in  the  most  prosperous  times,  at 
about  seven  millions ;  and  repeated  military  expeditions  into  Asia  and 
Ethiopia  had,  in  the  course  of  ages,  concentrated  in  it  immense  wealth, 
the  spoils  of  conquered  nations,  and  crowded  with  captives  and  slaves 
the  Valley  of  the  Nile. 

For  this  long  continuance  of  the  Egyptian  polity  satisfactory  reasons 
may  be  assigned.  In  early  ages,  when  maritime  expeditions  Ancient  condi- 
were  necessarily  feeble,  the  country  was  open  to  invasion  tion  of  Egypt, 
only  across  a  narrow  neck  of  land  on  the  east,  and  was  protected  from 
any  attack  on  the  west  by  impassable  and  interminable  deserts.  Under 


614  THE  EGYPTIANS. 

the  military  system  of  remote  antiquity  Egypt  was  almost  inaccessible ; 
but  through  the  changes  of  later  times,  and  ever  since  naval  expeditions 
have  been  carried  to  any  extent,  her  position  has  been  that  of  extreme 
weakness.  The  uniform  experience  of  twenty-five  centuries,  from  the 
Persian  wars  to  those  of  the  French  ^Revolution,  has  shown  that  the  pos- 
session of  the  mouths  of  the  river  is  equivalent  to  the  conquest  of  the 
country. 

In  the  security  of  this  inaccessible  retreat,  and  under  political  institu- 
tions of  a  favorable  character,  the  civilization  which  was  to  be  conferred 
on  the  white  man  originated.  For  a  succession  of  centuries,  industrial 
art,  and  its  parent,  natural  knowledge,  appear  to  have  undergone  a  steady 
development ;  perhaps,  as  in  other  countries  at  a  later  time,  advancing  in 
the  more  prosperous  political  seasons,  and  becoming  stationary  in  the 
decay  of  the  empire.  The  statements  furnished  to  us  by  Greek  authors 
are  of  very  little  value,  for  as  long  a  period  of  time  intervened  between 
the  first  Egyptian  kings  and  them  as  from  them  until  now.  It  is  rather 
from  the  monuments  of  the  Egyptians  that  we  must  judge.  Each  year 
since  their  country  has  been  open  to  investigation,  and  their  hieroglyphic 
system  understood,  the  impressions  we  have  received  of  their  intellectual 
advancement  have  been  more  and  more  favorable.  The  vocal  statue  of 
Memnon  at  Thebes,  it  is  said,  emitted  a  musical  sound  when  touched  by 
the  rays  of  the  sun.  In  the  light  of  modern  criticism,  every  obelisk  and 
monument  in  those  desolated  palaces  is  finding  a  voice. 

The  public  works  attest  to  this  day  the  greatness  and  permanence  of 
Manners  of  the  the  Egyptian  monarchy,  and  the  peculiarities  of  the  Egyp- 
Egyptians.  ^ian  mind.  From  the  statues  and  ruins  of  the  temples  of 
the  Greeks  we  see  what  a  vivid  perception  that  people  had  of  the  beauti- 
ful. The  statues,  and  tombs,  and  temples  of  the  Egyptians  offer  a  strik- 
ing contrast ;  the  useful  every  where  predominates.  The  vases  of  the  one 
were  adorned  with  emblematical  and  graceful  forms ;  the  tombs  of  the  oth- 
er were  covered  with  sculptures  and  paintings,  commemorating  the  ordi- 
nary pursuits  of  life,  and  various  processes  in  the  arts  and  manufactures. 

These  sculptures  and  paintings  show  to  what  an  extent  the  physical 
sciences  and  arts  depending  on  them  had  been  cultivated.  They  set  be- 
fore us  the  domestic  life  and  daily  business  and  trades  of  the  people : 
cookery,  confectionery,  glass-blowing,  weaving,  pottery-making,  manu- 
facture of  cotton,  painting  on  wood  and  stone,  staining  of  glass,  and  a 
hundred  other  occupations.  Among  the  pictured  representations,  a  chem- 
ist sees  with  pleasure  the  apparatus  of  his  art,  siphons,  bellows,  blow- 
pipes, etc. 

Shut  up  by  its  political  system  from  the  Mediterranean  nations  in  the 
same  manner  that  the  Chinese  and  Japanese  empires  have  been  in  later 
times  from  other  states,  Egypt  was  to  the  Greek  a  land  of  mystery  and 


INTRODUCTION   OF  WRITING.  615 

marvels.  The  exaggerated  legends  which  had  been  brought  from  it  at 
distant  intervals  by  those  who  had  escaped  by  stealth,  or  in  troublous 
times  had,  like  Cecrops  and  Danaus,  led  forth  colonies  of  emigrants,  lost 
none  of  their  wonders  in  the  traditions  of  successive  generations,  but 
were  rather  verified  by  the  roving  pirates  who  had  seen  the  pyramids, 
obelisks,  and  sphinxes,  and  the  great  temples  on  the  banks  of  the  Nile. 

The  first  step  in  civilization  is  the  invention  of  some  system  of  per- 
manent record — some  method  of  writing.  Without  this,  it  introduction 
may  be  truly  said  that  law  can  not  exist.  Law  can  not  main-  of  writing  from 
tain  itself  in  the  uncertainties  of  tradition — law,  without  Egypt* 
which  we  can  not  conceive  of  society.  The  legendary  history  of  Europe 
is  doubtless  correct  in  referring  to  some  of  these  Egyptian  fugitives  or 
emigrants  the  contemporaneous  introduction  of  writing,  and  a  system  of 
jurisprudence.  Even  if  the  former  was  derived  from  Phrenicia,  accord- 
ing to  the  story  of  Cadmus,  the  Phoenicians  had  originally  borrowed  it 
from  Egypt.  It  is  an  interesting  illustration  of  the  tendency  of  the  Eu- 
ropean mind  to  analysis,  that  of  the  forms  of  writing  known  in  those 
times,  the  ideographic  or  picture-writing,  the  syllabic  or  the  representa- 
tion of  syllable  sounds  by  signs,  and  the  alphabetic,  the  latter  alone 
maintained  its  foothold  in  Europe.  This  form,  as  described  at  page  356, 
essentially  consists  in  decomposing  articulate  expressions  into  their  con- 
stituent vowel  and  consonant  sounds,  and  assigning  for  each  of  those 
sounds  a  letter. 

About  seven  hundred  years  before  Christ,  events  took  place  which  led 
to  the  extension  of  Egyptian"  civilization  to  Europe.  The  an-  jntroduction 
cient  power  of  the  kings  had  declined,  through  disputes  and  of  Egyptian 
compromises  occurring  between  them  and  the  priesthood.  Be- 
tween the  priests  and  the  military  caste  there  was  an  open  quarrel,  many 
of  the  former  having  been  deprived  of  their  lands.  These  rivalries  broke 
out  in  revolts  and  insurrections,  and  for  two  years  the  country  was  in  a 
state  of  anarchy,  from  which  a  partial  respite  was  obtained  by  an  entire 
change  in  its  institutions.  Twelve  of  the  most  influential  persons  divided 
it  among  them,  each  having  a  province  which  he  ruled  as  an  independent 
king.  The  old  monarchy  had  degenerated  into  an  oligarchy,  and  it  was 
this  revolution  which  introduced  African  science  into  Europe. 

Psammetichus,  one  of  the  twelve,  had  for  his  province  the  country  which 
borders  on  the  Mediterranean  Sea.  Availing  himself  of  his  position,  he 
established  an  intercourse  with  the  neighboring  nations,  particularly  the 
Greeks  and  Phoenicians,  and  amassed  from  it  so  much  wealth  that  his 
colleagues,  jealous  of  his  increasing  power,  resolved  to  dispossess  him. 
Until  this  time,  all  foreigners  had  been  held  in  the  utmost  contempt,  and 
rigidly  excluded.  Psammetichus  called  in  the  aid  of  Ionian  pirates,  and 
other  Mediterranean  adventurers,  and,  having  collected  a  sufficient  body 


616  THE   PERSIAN   EMPIRE. 

of  such  mercenaries,  defeated  his  colleagues  at  the  battle  of  Momemphis, 
and  "became  sole  ruler  of  the  whole  country. 

By  the  aid  of  a  foreign  force  the  revolution  had  been  ended,  but  the 
Opening  of  the  position  of  Psammetichus  was  essentially  different  from  that 
ports  of  Egypt.  of  all  preceding  princes.  A  foreign  force  had  given  him  the 
throne,  and  a  foreign  force  alone  could  maintain  him  on  it.  Under  such 
circumstances,  he  took  his  most  politic  course,  and,  breaking  through  the 
traditions  of  twenty-five  centuries,  opened  the  ports  of  Egypt. 

This  event  necessarily  led  to  a  closer  intercourse  among  the  Mediter- 
ranean nations,  and  insured  communication  between  Europe  and  Africa. 
The  foreign  element  quickly  made  its  influence  manifest.  In  the  very 
next  reign  the  Cape  of  Good  Hope  was  doubled,  and  Africa  circumnavi- 
gated, and  in  the  course  of  a  very  few  years  we  find  Pythagoras,  Solon, 
and  Thales  visiting  Egypt,  and  bringing  from  thence  to  Europe  the  ele- 
ments of  law  and  natural  science. 

The  Persian  empire  in  the  mean  time  had  attained  an  attitude  of  su- 
The  Persian  Premacy  in  Western  Asia.  Following  the  inspirations  of  its 
empire:  its  in-  Babylonian  predecessors,  it  was  engaged  in  continual  wars 
with  its  African  neighbor.  From  the  battle  of  Pelusium, 
and  the  conquest  of  Egypt  by  Cambyses,  the  political  interests  of  that 
country  and  Greece  became  essentially  the  same.  The  Persian  con- 
querors, operating  alternately  on  the  north  and  south  shores  of  the  Medi- 
terranean, betrayed  a  determination  to  extend  their  rule  around  that  sea, 
and  make  it  a  Persian  lake.  On  the  one  hand  they  were  resisted  by  the 
Greeks,  on  the  other  by  the  Egyptians,  between  whom  active  communi- 
cations were  kept  up.  For  several  centuries  these  operations  were  con- 
ducted with  various  success.  The  kings  of  Persia,  several  of  whom 
seem  to  have  been  men  of  great  capacity,  comprehended  the  political  ad- 
vantages which  would  arise  from  the  possession  of  the  sea,  and  would 
have  doubtless  carried  out  their  plans  as  respects  the  south  shore,  if  the 
Phoenicians  had  not  opposed  obstacles  for  the  sake  of  their  colony  at 
Carthage.  And  though  the  Greek  historians,  with  a  pardonable  motive, 
speak  of  the  various  movements  on  the  north  as  failures,  there  are  many 
circumstances  which  lead  us  to  receive  their  accounts  with  allowances. 
If  Memphis  was  sacked,  Athens  also  was  burned ;  and  even  at  the  open- 
ing of  the  Macedonian  expedition,  Greek  history  is  full  of  Persian  inci- 
dents and  intrigues. 

In  speaking  of  the  Egyptian  cultivators  of  philosophy  as  priests,  the 
Introduction  of  signification  which  is  now  attached  to  that  word  gives  us  an 
Egyptian  phi-  erroneous  idea  of  what  they  really  were.  The  colleges  at 
Memphis,  Thebes,  Heliopolis,  and  Sais,  were,  in  reality,  each 
the  head-quarters  of  a  fraternity  of  artists  and  professional  men,  and  bore 
no  sort  t>f  resemblance  to  our  modern  ecclesiastical  institutions.  Among 


THE  GREEK  SCHOOLS.  617 

them  were  architects,  lawyers,  physicians,  painters,  chemists,  astrono- 
mers. These  men  were,  moreover,  the  great  landowners  ;  not  only  were 
the  temples  richly  endowed  as  corporations,  but  the  individual  members 
were  persons  of  wealth.  They  enjoyed  monopolies  of  all  kinds ;  for  in- 
stance, among  other  things  they  had  extensive  factories  for  cottons,  and 
laboratories  for  the  preparation  of  chemical  products. 

From  these  institutions  the  Greek  philosophers  brought  natural  sci- 
ence. Pythagoras  had  resided  at  Thebes,  Thales  and  Democ-  The  Greek 
ritus  at  Memphis,  Plato  at  Heliopolis,  Solon  at  Sais.  They  schools- 
did  at  first  little  more  than  expound  the  doctrines  they  had  learned. 
Their  mode  of  instruction  seems  to  have  been,  in  many  instances,  found- 
ed on  the  Egyptian  model.  The  Pythagorean  establishment  at  Crotona 
may  be  regarded  as  a  partial  imitation  of  the  African  colleges. 

It  is  not  my  intention  to  enter  on  an  examination,  or  even  enumera- 
tion, of  ancient  philosophical  opinions,  nor  to  show  that  many  of  the  doc- 
trines which  have  been  brought  forward  within  the  last  thtee  centuries 
existed  in  embryo  in  those  times.  It  may,  however,  be  observed  that, 
in  the  midst  of  much  error,  there  were  those  who  held  just  views  of  the 
various  problems  of  theology,  law,  politics,  philosophy,  and  particularly 
of  the  fundamental  doctrines  of  natural  science,  the  constitution  of  the  so- 
lar system,  the  geological  history  of  the  earth,  the  nature  of  chemical 
forces,  the  physiological  relations  of  animals  and  plants. 

It  is  supposed  by  many,  whose  attention  has  been  casually  drawn  to 
the  philosophical  opinions  of  antiquity,  that  the  doctrines  which  we  still 
retain  as  true  came  to  the  knowledge  of  the  old  philosophers  not  so  much 
by  processes  of  legitimate  investigation  as  by  mere  guessing  or  crude 
speculation,  for  which  there  was  an  equal  chance  whether  they  were  right 
or  wrong ;  but  a  closer  examination  will  show  that  many  of  them  must 
have  depended  on  results  previously  determined  or  observed  by  the  Af- 
ricans or  Asiatics,  and  thus  they  seem  to  indicate  that  the  human  mind 
has  undergone  in  twenty  centuries  but  little  change  in  its  manner  of  ac- 
tion, and  that,  commencing  with  the  same  data,  it  always  comes  to  the 
same  conclusions.  Nor  is  this  at  all  dependent  on  any  inherent  logic  of 
truth.  Very  many  of  the  errors  of  antiquity  have  reappeared  in  our 
times.  If  the  Greek  schools  were  infected  with  materialism,  pantheism, 
and  atheism,  the  later  progress  of  philosophy  has  shown  the  same  char- 
acters. To  a  certain  extent,  such  doctrines  will  receive  an  impression 
from  the  prevailing  creeds,  but  the  arguments  which  have  been  appealed 
to  in  their  favor  have  always  been  the  same.  The  distinction  between 
these  heresies  in  ancient  and  modern  times  lies  chiefly  in  the  grosser 
characters  which  they  formerly  assumed,  arising  partly  from  the  reflected 
influence  of  the  existing  mythology,  and  partly  from  the  imperfections 
of  exact  knowledge.  Even  the  errors  of  early  antiquity  are  venerable. 


618  ANALYTICAL  MIND   OF  THE   EUROPEAN. 

We  must  judge  our  predecessors  by  the  same  rules  that  we  hope  pos- 
terity will  judge  us,  making  a  generous  allowance  for  the  imperfections 
of  reason,  the  infirmities  of  character,  and  especially  for  the  prejudices 
of  the  times.  To  have  devoutly  believed  in  the  existence  of  a  human 
soul,  to  have  looked  forward  to  its  continuing  after  the  death  of  the 
body,  to  have  expected  a  future  state  of  rewards  and  punishments,  and 
to  have  drawn  therefrom,  as  a  philosophical  conclusion,  the  necessity  of 
leading  a  virtuous  life — these,  though  they  may  be  enveloped  in  a  cloud 
of  errors,  are  noble  results  of  the  intellect  of  man. 

The  analytical  quality  of  the  European  mind  already  manifested  itself 
Analytical  in  this  decomposition  of  knowledge  derived  from  foreign  coun- 
Eurcfean **"*  tries,  in  this  establishment  of  a  host  of  schools,  this  examina- 
mind.  tion  and  discussion  of  the  fundamental  elements  of  the  im- 

ported philosophy.  As  there  are  differences  in  the  physiognomy  of 
races,  so  there  are  differences  in  their  intellectual  endowments,  which, 
arising  in  peculiarities  of  cerebral  construction,  communicate  peculiarities 
to  the  processes  of  thinking.  The  physical  science  of  Egypt,  transported 
to  Greece,  rapidly  degenerated  into  speculative  philosophy,  and  in  so 
doing  produced  an  instability  of  opinion  which  entailed  as  its  conse- 
quence a  laxity  of  morals.  Such  a  social  condition  led  naturally  to  the 
results  which  history  indicates.  It  is  not  surprising  that  the  most  em- 
inent men  were  open  to  bribery,  and  that  the  glory  of  those  ages  was  so 
often  the  brilliancy  of  corruplion.  These  are  the  necessary  results  at- 
tending such  political  conditions.  Too  often  it  fell  out  that  the  great 
men  of  Greece  accused,  and  too  often  convicted  each  other  of  being  in- 
fluenced by  Persian  intrigues  and  Persian  gold.  In  the  general  demor- 
alization, they  seem  to  have  taken  for  their  guide  a  perverted  interpreta- 
tion of  the  admirable  precept  of  Solon,  "  In  every  thing  thou  doest,  con- 
sider the  end." 

Added  to  this,  the  public  faith  in  things  once  implicitly  believed  was 
shaken.  Xerxes  in  a  very  unceremonious  way  violated  the  temples  and 
carried  off  their  treasures,  showing  the  same  contempt  for  the  gods  of 
Europe  that  Cambyses  had  shown  for  those  of  Africa.  If  there  lingered 
in  the  minds  of  the  philosophers  any  latent  belief  in  the  national  faith,  a 
relic  of  the  impressions  of  childhood  or  of  popular  opinion,  such  a  prac- 
Greek  irre-  tical  demonstration  could  scarcely  be  lost.  During  the  fifty 
ligion.  years  of  that  war,  the  philosophical  opinions  of  the  Persians 
had  full  opportunity  to  find  their  way  among  a  class  of  men  quite  open 
to  receive  them,  and  from  this  time  we  perceive  a  striking  similarity  be- 
tween many  of  the  doctrines  of  the  schools  and  the  well-known  dogmas 
of  the  Orientals.  The  Greeks,  like  the  Hindoos,  in  the  possession  of  the 
mere  rudiments  of  science,  passed  at  once  to  the  discussion  of  the  most 
important  and  elevated  problems  with  which  the  human  mind  can  be  en- 


ORIGIN  OF  EUROPEAN   COMMERCE.  619 

gaged,  and,  as  an  inevitable  consequence,  were  led  away  from  true  phi- 
losophy into  sophistry  and  irreligion. 

It  has  been  remarked  a  few  pages  back,  that  in  the  progress  of  nations 
events  follow  in  repeating  cycles,  and  that  for  any  one  we  may  generally 
find  its  precursor,  and  therefore  its  prognostic.  Greece  dealt  with  the 
philosophy  she  had  received  from  the  southern  people,  African  or  Asi- 
atic, exactly  in  the  same  manner  that  Europe  dealt  with  Italian  theology 
the  moment  that  liberty  of  action  was  permitted  by  the  Reformation.  In 
each  case  the  issue  was  not  the  prompt  and  final  substitution  of  a  sys- 
tem correcting  apparent  and  acknowledged  defects,  a  system  in  unison 
with  the  existing  tone  of  thought.  There  was  no  such  stoppage  of  ac- 
tion ;  but  from  the  bosom  of  each  principle  and  sect  many  other  princi- 
ples and  sects  arose,  until  there  seemed  to  be  no  end  to  the  subdivision. 

If  thus  we  consider  the  political  position  of  Greece,  the  condition  of 
Asia  Minor,  occupied  by  Persian  troops,  the  destruction  that  influence  of  the 
had  overtaken  Egypt,  the  excitements  and  calamities  of  a  war  ^mod'eraphi- 
of  half  a  century,  we  can  readily  understand  that  this  was  losophy. 
not  a  season  when  the  tedious  and  slow  processes  of  true  philosophy  were 
likely  to  flourish,  and  that  it  was  far  more  conducive  to  imposture  than 
to  science.  The  seeds  of  knowledge  which  had  been  brought  from 
Egypt  shot  up  into  a  rank  growth,  and  Europe  did  not  free  herself  of 
these  weeds  for  sixteen  centuries.  The  character  of  a  long  train  of 
events  is  often  determined  at  its  inception ;  for  this  reason,  I  have  dwelt 
in  detail  on  those  times,  and  it  is  well  worthy  of  remark  that  the  posi- 
tive science  of  the  European  was  not  fairly  established  until  after  three 
distinct  impulses  from  Egypt :  once,  as  we  have  seen,  under  her  Pha- 
raohs ;  again,  under  her  Ptolemies ;  and  still  again,  under  her  Caliphs 
and  Sultans. 

While  these  events  were  taking  place  in  the  southeast  of  Europe,  do- 
mestic and  foreign  commerce  were  preparing  the  way  for  a  Ori  -n  of  Eu 
gradual  diffusion  of  civilization.  A  trade  with  the  countries  ropean  coin- 
bordering  on  the  Baltic  Sea  for  the  amber  which  is  found  on  J 
those  shores  had  gradually  arisen,  and,  in  like  manner,  another  with 
Spain,  France,  and  England  for  tin.  The  tin  of  Cornwall  was  carried 
through  France  and  shipped  by  the  Phoenicians  at  Marseilles,  a  certain 
quantity  of  the  same  metal  being  also  obtained  from  the  Spanish  mines. 
Early  in  their  history  the  Phoenicians  had  established  colonies  on  several 
points  of  the  Black  Sea,  and  from  these  depots  they  brought  the  various 
products  of  those  countries,  among  which  may  be  mentioned  gold,  which 
had  apparently  been  originally  derived  from  the  washing  of  the  Uralian 
deposits.  This  Black  Sea  commerce  seems,  however,  to  have  been  event- 
ually abandoned  for  the  more  profitable  Spanish  trade,  and  on  the  with- 
drawal of  the  Phoenicians  from  the  Euxine,  the  Greeks  occupied  their 


620  THE   MACEDONIAN    CAMPAIGN. 

Discover  of  P^ace*  Meantime  the  enterprise  of  the  Tyrian  sailors  had 
the  straits  of  carried  them  through  the  Straits  of  Gibraltar,  and  enabled 
Gibraltar.  them  to  have  direct  access  with  the  tin  and  amber  countries 
without  the  intervention  of  any  overland  traffic.  It  was  doubtless  the 
discovery  of  this  outlet  to  the  Atlantic  which  led  to  the  destruction  of 
the  Gaulish  trade  in  tin  and  the  German  trade  in  amber.  So  greatly 
was  this  latter  substance  prized,  that  the  overland  commerce  in  it  had 
many  ramifications  :  thus  amber  was  carried  into  Italy  by  the  Etruscans, 
who  had  a  sacred  road  under  the  protection  of  the  adjacent  tribes  to  the 
Baltic  Sea. 

With  their  commerce  the  Phoenicians  disseminated  a  knowledge  of 
many  inventions  peculiar  to  themselves,  among  which  may  be  mentioned 
the  use  of  stamped  metallic  coinage.  Their  great  African  colony,  Car- 
thage, exerted  in  these  movements  eventually  a  more  powerful  influence 
than  even  the  parent  country. 

Emulating  the  enterprise  of  the  Phoenicians,  the  Greek  mariners  un- 
dertook expeditions  both  to  the  east  and  to  the  west,  succeeding,  as  we 
have  seen,  in  establishing  themselves  on  the  shores  of  the  Euxine,  and 
eventually  passing,  under  Colceus  of  Samos,  through  the  Straits  of  Gib- 
raltar into  the  Atlantic  Ocean;  but  even  up  to  the  time  of  the  Mace- 
The  Macedoni-  donian  expedition,  their  geographical  ideas  were  very  crude 
an  campaign.  an(j  fun  Of  errors.  Of  the  expedition  of  Alexander,  Hum- 
boldt  remarks  that  it  partook  as  much  of  the  character  of  a  scientific  as 
of  a  military  undertaking,  and  its  consequences,  both  immediate  and  re- 
mote, upon  Europe  can  scarcely  be  exaggerated.  That  great  commander 
surrounded  himself  with  whatever  talent  was  to  be  found  in  Greece,  and 
made  his  military  successes  for  a  time  subservient  to  the  science  of  his 
native  country.  It  was  through  this  that  Aristotle  obtained  that  com- 
manding influence  which  not  only  gave  him  an  authority  over  the  active 
mind  of  his  own  times,  but  which  was  felt  even  until  the  introduction  of 
the  Baconian  system  of  philosophy.  The  campaigns  of  Alexander  doub- 
led the  geography  of  the  Greeks  in  longitude,  opened  to  their  investi- 
gation new  countries  even  to  the  tropics,  brought  them  acquainted  with 
races  of  men  who  had  been  the  depositaries  of  science,  as  it  then  existed, 
for  thousands  of  years,  and,  in  short,  added  Asiatic  to  Grecian  knowl- 
edge. It  is  a  significant  fact  that,  after  the  taking  of  Babylon,  Alexander 
sent  to  Aristotle  a  series  of  astronomical  observations  reaching  back 
through  1903  years. 

The  Macedonian  expedition  not  only  made  a  profound  impression  on 

Restoration  of  ^e  European  mind  by  its  immediate  results — its  influence  is 

monarchy  in     equally  palpable  in  its  remoter  consequences.     It  would  be 

impossible,  in  such  a  sketch  as  this,  to  do  justice  to  that  great 

event  in  all  its  details ;  for  nations  can  not  be  thus  brought  in  contact 


THE  PTOLEMIES.  621 

without  prodigious  mental  results,  the  extinction  of  old,  and  the  appear- 
ance of  new  ideas.  But  of  the  influences  which  thus  arose,  there  is,  how- 
ever, one  which  deserves  to  fasten  our  attention,  and  the  more  so  since 
we  have  had  already,  and  shall  have  again,  the  occasion  for  alluding  to 
it.  It  was  the  establishment  of  a  regal  government  in  Egypt.  Under 
the  Ptolemies,  who  may  "be  truly  characterized  as  the  most 

„         T  ,  J  ,    The  Ptolemies. 

illustrious  kings  of  antiquity,  that  ancient  country  recovered 
her  pristine  glory.  Among  the  works  accomplished  by  these  great  men 
may  be  mentioned,  as  examples  of  their  high-toned  policy,  the  sending 
out  an  exploring  expedition  to  equinoctial  Africa ;  the  establishment  of 
menageries  and  zoological  gardens  at  Bruchium ;  their  attempts  at  determ- 
ining the  cause  of  the  overflow  of  the  Nile ;  the  library  at  Alexandria ; 
the  museum  at  Ehakotis ;  the  measurement  of  a  degree  on  the  earth's 
surface  between  Alexandria  and  Syene ;  the  ascertaining  of  the  prodigious 
distance  of  the  region  of  the  fixed  stars ;  the  recognition  of  the  motion 
of  rotation  of  the  earth  upon  her  axis,  and  of  her  translation  around  the 
sun ;  the  precession  of  the  equinoxes ;  the  attempt  at  constructing  a  map 
of  the  world  by  the  aid  of  degrees,  based  on  lunar  observations  and  on 
shadows  ;  the  improvement  of  the  methods  of  astronomical  observation 
by  the  invention  of  water-clocks,  and  instruments  for  the  more  accurate 
measurement  of  angles.  Along  with  these,  Baron  Humboldt,  in  his  Cos- 
mos, has  enumerated  many  other  philosophical  works  of  the  Ptolemies, 
which  exerted  a  profound  influence  both  upon  the  knowledge  and  intel- 
lect of  Europe.  Greece  now  repaid  what  she  had  formerly  borrowed ; 
her  schools  of  philosophy  were  translated  to  Alexandria,  and  the  great 
names  of  Euclid,  Apollonius,  and  Archimedes  testify  to  the  return  of 
those  ages  to  exact  science. 

The  decline  of  Greece  and  her  final  absorption  into  the  Roman  em- 
pire was  the  necessary  consequence  of  her  mode  of  life.  In  Decline  of 
policy  as  in  philosophy,  her  essential  tendency  was  to  sub-  riseeof'thedRo- 
division,  and  therefore  to  weakness.  In  her  external  rela-  man  empire, 
tions  she  had  ever  been  far  more  closely  connected  with  Asia  than  with 
Europe.  For  a  long  time  she  was  little  more  than  an  outlying  territory 
of  Persia,  respecting  and  fearing  the  highly-civilized  nations  in  her  front, 
but  scarcely  concerning  herself  with  the  barbarians  at  her  back.  Very 
different  was  it  with  Rome,  her  great  supplanter  and  successor,  who, 
thoroughly  European  in  her  whole  history,  exercised  an  active,  interven- 
tion in  the  affairs  of  adjacent  nations — an  influence  perpetually  felt 
through  Spain,  Germany,  Gaul,  and  Britain. 

It  is  difficult  to  estimate  fully  the  influence  of  the  Roman  empire  on 
the  intellect  of  Europe.  Its  power  lay  not  in  the  origination  of  what  was 
new,  but  in  the  development  and  dissemination  of  what  was  derived  from 
other  sources.  The  contributions  of  the  Roman  emperors  to  the  stock 


622  THE  ROMAN   EMPIRE. 

of  positive  knowledge  bear  no  kind  of  comparison  to  that  of  the  Ptole- 
mies just  mentioned;  indeed,  their  works  have  reference  chiefly  to  military 
purposes  and  material  aggrandizement.  In  this  manner  we  must  look 
upon  the  surveys  and  itineraries  which  they  caused  to  be  made  of  vari- 
ous parts  of  the  empire.  Nevertheless,  through  their  influence  the  idea 
of  civilization  was  gradually  made  to  find  its  way  through  Central  and 
Northern  Europe. 

The  function  of  Rome  in  our  history  is  very  distinct.  From  small 
Centralizing  beginnings  she  steadily  pursued  the  same  progress.  The 
pote™^11^  c011*!1168*  an^  absorption  of  town  after  town,  which  was  the 
Home.  history  of  her  earlier  times,  was  carried  out  in  the  annexation 

of  nations  in  her  day  of  strength.  From  the  moment  that  she  gained 
the  control  of  the  Mediterranean  Sea,  which  was  the  grand  epoch  of  her 
life,  she  inexorably  forced  all  the  conterminous  nations  to  acknowledge 
Italian  centralization.  It  is  no  metaphorical  expression  that  she  became 
their  centre  of  gravity.  No  circumstance  could  occur  to  her  which  did 
not  instantly  influence  them  all.  As  far  more  than  an  equivalent  for 
subjugation  and  loss  of  independence,  she  made  them  into  a  common 
race,  harmonizing  their  actions,  and  giving  them  common  ideas.  The 
Roman  empire  was  the  organizing  agent  of  the  white  man. 

The  acts  of  man,  though  they  may  have  the  aspect  of  free-will  as  re- 
gards himself,  are  automatic  as  regards  the  race.  He  is  employed  in 
achieving  a  result  of  which  he  is  utterly  ignorant ;  he  is  concerned  in  a 
work  of  the  effects  of  which  he  is  unconscious.  He  is  like  a  bee,  which 
doubtless  experiences  a  certain  pleasure  in  flying  from  flower  to  flower, 
the  gratification  of  an  obscure  desire  in  constructing  cell  after  cell,  its 
individual  delight  ministering  to  a  public  good  of  the  nature  of  which  it 
is  wholly  unconscious. 

In  such  a  manner  we  may  look  upon  the  career  of  the  Roman  with 
satisfaction.  He  was  pursuing  a  life  of  evil  deeds,  and  accumulating  in 
his  great  and  dissipated  capital  the  spoils  of  wasted  provinces,  gratifying 
his  wanton  luxuries  by  a  systematic  resort  to  war,  that  most  awful  of 
the  curses  that  afflict  our  race.  It  was  the  temporary  lust  of  individual 
interest  that  he  was  pursuing.  Providence  was  bringing  out  of  it  a  uni- 
versal good. 

If  Rome  was  cruel  in  her  national  acts,  she  was  majestic  in  her  policy. 
The  fall  of  Eu  ^e  decimated  nations  that  she  might  bind  them  into  one 
ropean  pagan-  family.  With  remorseless  vigor  she  extinguished  every 
trace  of  independent  action,  and  with  a  contradictory  but 
noble  liberality,  domesticated  the  worship  of  every  conquered  people 
round  the  Capitol.  There  was  no  god  whose  image  she  could  not  show, 
no  faith  of  which  she  was  not  the  patroness.  It  may  serve  as  an  exam- 
ple of  the  manner  in  which  her  policy  led  to  definite  results  of  which  she 


THE   PAPAL   GOVERNMENT.  623 

was  unaware,  or,  if  aware,  of  the  manner  in  which  the  strong  hand  of 
Providence  inverted  her  designs,  that  by  this,  her  system  of  universal 
toleration  of  every  ancient  faith,  /she  absolutely  destroyed  them  all. 
Brought  thus  to  bear  upon  one  another  at  a  common  central  point,  their 
contradictions,  inconsistencies,  fallacy,  and  emptiness  became  apparent. 
The  men  of  capacity  first  made  the  detection,  their  opinions  spreading 
by  degrees  through  society.  Well  might  St.  Chrysostom  say  that  the 
error  of  idolatry  vanished  of  itself,  and  that  paganism  seemed  in  his  day 
"  like  a  conquered  city,  whose  walls  were  overthrown,  her  halls,  theatres, 
and  public  buildings  consumed  by  fire,  her  defenders  slain,  and  here  and 
there  a  few  old  men  and  children  lingering  among  the  ruins.  Even 
these  were  soon  found  no  more." 

It  is  sometimes  said  that  the  Boman  empire  was  essentially  composed 
of  cities ;  that  at  its  fall  its  fragments  were  cities ;  and  that  it  left  nothing 
to  posterity  but  its  municipal  system.  Such  a  statement  is  not  true. 
Its  legacy  was  of  a  far  higher  order.  It  left  the  religion  it  had  adopted, 
the  civil  law,  and  the  foreshadowing  of  the  great  deeds  that  might  be  ac- 
complished by  the  white  man  organized  and  united.  To  this,  in  a  more 
perfect  way,  the  affairs  of  our  times  are  still  conspicuously  tending.  We 
begin  to  hear  of  the  opinion  of  Europe,  the  public  law  of  Europe,  expres- 
sions which  are  gaining  each  day  more  and  more  significance. 

In  that  phantasmagorial. exhibition  which  we  call  history,  events  give 
birth  to  events  as  in  dissolving  views,  the  phantoms  of  the  influenceoftlie 
actors  stalking  one  after  another.  It  is  not  always  possible  empire  in  its 
for  us,  with  the  slender  information  we  possess,  to  determine 
the  time  of  origin  of  etch  incident,  or  its  true  and  actual  bearings.  The 
secret  history  of  antiquity  is  almost  unknown.  Nearly  every  circum- 
stance in  the  decline  of  the  Roman  empire  was  fraught  with  important 
consequences  for  modern  times.  Among  the  more  obvious  facts  which 
attract  our  attention  are  the  dislocation  of  the  centre  of  the  empire  by 
the  translation  of  the  seat  of  government  to  Constantinople,  the  conse- 
quent acquisition  of  power  by  the  bishops  of  Home  in  the  West,  the  in- 
cessant emigrations  and  invasions  of  barbarians  from  the  North,  the  con- 
quests of  the  Saracens,  from  whom  it  seemed  af  one  time  that  Europe 
would  hardly  escape,  and  that  the  threat  of  Muza  would  come  to  pass, 
that  the  name  of  Mohammed  should  be  proclaimed  in  the  Vatican ;  the 
consolidation  of  ecclesiastical  policy,  and  the  repeated  attempts  of  the 
Church  to  suppress  barbarism — attempts  so  signally  successful  that  by 
the  end  of  the  eighth  century  many  of  those  nations  had  written  systems 
of  law ;  the  separation  of  the  Greek  and  Latin  Churches,  the  The  Papal 
different  phases  which  the  latter  assumed  as  she  was  affected  government, 
by  existing  circumstances,  how  she  extricated  herself  from  an  almost 
barbarous  state  after  the  empire  had  failed  her,  how  she  asserted  the  in- 


624  SUPPRESSION  OF  PHILOSOPHY. 

dependence  of  the  spiritual  order,  how  she  kept  her  grasp  upon  mankind 
by  the  establishment  of  monastic  institutions ;  how,  after  the  death  of 
Charlemagne,  who  had  done  so  much  for  her,  she  adopted  the  feudal 
system,  which  was  the  legitimate  offspring  of  barbarism ;  how,  as  knowl- 
edge began  to  spread,  she  tried  to  render  it  tributary  to  her  by  councils, 
convocations,  federations ;  how,  finding  it  likely  to  become  uncontrollable, 
she  took  the  alarm,  and  in  an  evil  hour  attempted  its  repression ;  how 
for  a  little  while  she  became  the  autocrat  of  Europe,  and  in  the  plenitude 
of  her  power  so  greatly  forgot  her  duty  that,  in  the  time  of  Leo  X.,  it 
was  doubted  in  Rome  whether  the  soul  be  immaterial  and  immortal, 
Erasmus  testifying  with  horror  that  he  heard  it  proved  that  there  is 
no  difference  between  the  soul  of  a  man  and  that  of  a  beast — of  a  truth 
it  was  said  that  the  Eternal  City  teemed  at  once  with  all  crime  and  all 
the  glories  of  art — how,  against  the  moral  and  intellectual  revolt  which 
she  encountered — the  Reformation — the  Church  made  a  stand  by  the  aid 
of  the  Society  of  the  Jesuits  and  the  establishment  of  the  Inquisition, 
Its  attem  t  at  an<^'  w^  a  quick  sense  of  her  true  position,  attempted  to 
suppressing  guide  children  through  education  by  the  former,  and  to  check 
philosophy.  men  ^  the  terrors  of  the  iatter;  hOWj  as  if  ^  instinct,  she 

detected  the  antagonism  of  exact  science,  and  on  the  one  hand  published 
her  Index  of  prohibited  books,  and  on  the  other  allied  herself  with  art, 
cultivating  it  so  eminently  as  to  compel  even  her  enemies  to  confess  that 
she  had  produced  true  miracles  at  last — in  architecture,  sculpture,  paint- 
ing, music.  Pius  IV.  was  justified  in  comparing  some  of  her  grand 
masses  to  the  strains  of  Paradise. 

The  mistake  committed  by  the  Italian  governmftnt  in  thus  attempting 
the  compression  of  human  thought  was  in  its  imperfect  appreciation  of 
the  qualities  of  the  European  mind  and  the  existing  philosophical  tend- 
ency. Up  to  a  certain  point  opinion  may  be  coerced  by  force.  It  is 
altogether  a  vulgar  error  that  persecution  never  attains  its  ends.  In 
nine  cases  out  often  it  does  attain  them,  provided  it  is  applied  with  suf- 
ficient severity  and  for  a  sufficient  time,  as  is  proved  by  the  history  of 
almost  any  nation ;  but  in  the  tenth  it  fails. 

Judging  from  the  experience  of  twenty  centuries,  for  that  was  nearly 
Failure  of  that  the  period  during  which  the  European  had  been  philosophiz- 
attempt.  jng?  the  popes  were  justified  in  coming  to  the  conclusion  that 
they  did.  Those  centuries  had  produced  no  philosophy  of  a  sure  and 
permanent  kind.  The  only  fruit  which  they  had  borne  was  the  meta- 
physical uncertainties  of  the  schools.  There  seemed  no  prospect  that  the 
human  mind  would  ever  do  more  than  flounder  in  doubt ;  that  sect  after 
sect,  and  doctrine  after  doctrine,  would  emerge  into  prominence  and  disap- 
pear. In  such  a  state  of  things,  it  was  not  to  be  supposed  that  any  peril 
could  arise  from  attempting  to  control  opinion  by  authority,  and  to  extin- 
guish the  spirit  of  inquiry  by  asserting  the  paramount  efficacy  of  faith. 


THE   REFORMATION.  625 

In  thus  failing  to  recognize  the  fact  that  things  were  coming  to  that 
condition  in  which  the  elements  of  certainty  and  absolute  philosophical 
truth  would  be  shortly  attained,  the  popes  committed  the  Church  to  an 
irreparable  error.  They  periled  her  authenticity  in  an  unequal  conflict. 
It  might  do  for  a  little  time  to  deny  and  denounce  the  globular  figure  of 
the  earth,  but  the  demonstration  of  the  truth  came  irresistibly  at  last ; 
and  so  with  the  doctrines  of  the  antipodes,  the  daily  rotation  on  an  axis, 
<ind  the  annual  translation  round  the  sun.  It  enhanced  the  folly  of  these 
proceedings  that  they  were,  in  reality,  insincere.  Of  the  great  ecclesias- 
tics there  probably  were  none  who  did  not  privately  admit  the  truth  of 
what  was  thus  condemned.  When  the  bark  Vittoria,  of  Magellan's 
squadron,  made  the  first  voyage  of  circumnavigation  round  the  globe,  it 
was  a  high  Church  dignitary,  Cardinal  Contarini,  who  gave  the  true  ex- 
planation of  the  circumstance,  then  first  remarked,  of  the  loss  of  one 
whole  day  in  her  reckoning.  Such  insincerity,  and  the  issue  of  these 
and  other  like  questions,  could  end  in  no  other  way — they  sapped  the 
prestige  of  the  Church.  How  different  would  it  have  been  if  she  had 
taken  the  lead,  and  directed  the  human  mind  in  the  channels  through 
which  it  was  destined  to  pass,  instead  of  opposing  herself  as  an  obstacle! 
She  might  have  guided,  but  she  could  not  resist. 

It  is  to  be  remarked  that  the  men  who,  from  the  twelfth  to  the  six- 
teenth century,  distinguished  themselves  in  precipitating  the  The  Reforma- 
result,  were  mostly  ecclesiastics.  Roger  Bacon  may  be  taken  tion< 
as  the  type  of  them  all.  Their  labors  had  no  little  connection  with 
the  Eeformation  which  was  headed  by  Luther.  Though  we  are  accus- 
tomed to  regard  this  with  the  most  profound  interest,  a  more  philosoph- 
ical view  of  the  state  of  things  may  perhaps  suggest  that  it  is,  in  real- 
ity, only  one  act  of  a  great  drama.  We  should  not  mistake  an  episode 
for  the  main  event.  The  Reformation  soon  reached  its  full  expression 
in  dividing  Christendom.  Geographically  it  culminated  in  1648,  at  the 
treaty  of  Westphalia.  By  the  philosopher  it  will  ever  be  contemplated 
with  unalloyed  satisfaction,  for  it  asserted  as  its  chief  doctrine  the  right 
of  the  human  mind  to  judge  for  itself,  a  doctrine  so  unspeakably  precious 
as  to  make  of  no  account  the  inconveniences  which  arise  in  its  practical 
application  from  the  continual  multiplication  of  sects. 

In  the  history  of  the  European,  from  the  time  of  the  Emperor  Con- 
stantine  to  the  eighteenth  century,  the  ecclesiastical  element  influence  of 
so  greatly  preponderates  as  to  constitute  its  almost  essential  the  Christian 
feature ;  and,  after  all,  it  is  impossible  to  do  justice  to  the  ropean  civffi- 
effects  which  ensued  on  the  establishment  of  Christianity,  zation- 
and  its  adoption  by  the  white  man  as  his  religion.    The  civil  law  exert- 
ed an  exterior  power  in  human  relations ;  this  produced  an  interior  and 
moral  change.    The  idea  of  an  ultimate  accountability  for  personal  deeds, 

RE 


626  THE    CHRISTIAN   CHURCH. 

of  which  the  old  Europeans  had  an  indistinct  perception,  became  intense 
and  precise ;  the  sentiment  of  universal  charity  was  exemplified  not  only 
in  individual  acts,  the  remembrance  of  which  soon  passes  away,  but  in  the 
more  permanent  institution  of  establishments  for  the  relief  of  affliction, 
the  spread  of  knowledge,  the  propagation  of  truth.  Of  the  great  ecclesias- 
tics, many  had  risen  from  the  humblest  ranks  of  society,  and  these  men, 
true  to  their  democratic  instincts,  were  often  found  to  be  the  inflexible 
supporters  of  right  against  might.  Eventually  coming  to  be  the  deposi- 
taries of  the  knowledge  that  then  existed,  they  opposed  intellect  to  brute 
force,  in  many  instances  successfully,  and,  by  the  example  of  the  organi- 
zation of  the  Church,  which  was  essentially  republican,  they  showed  how 
representative,  systems  may  be  introduced  into  the  state.  Nor  was  it 
over  communities  and  nations  that  the  Church  displayed  her  chief  power. 
Never  in  the  world  before  was  there  such  a  system.  From  her  central 
seat  at  Eome  her  all-seeing  eye,  like  that  of  Providence  itself,  could  equal- 
ly take  in  a  hemisphere  at  a  glance,  or  examine  the  private  life  of  any 
individual.  Her  boundless  influences  enveloped  kings  in  their  palaces, 
or  relieved  the  beggar  at  the  monastery  gate.  In  all  Europe  there  was 
not  a  man  too  obscure,  too  insignificant,  or  too  desolate  for  her.  Sur- 
rounded by  her  solemnities,  every  one  received  his  name  at  her  altar ;  her 
bells  chimed  at  his  marriage,  her  knell  tolled  at  his  funeral.  She  ex- 
torted from  him  the  secrets  of  his  life  at  her  confessionals,  and  punished 
his  faults  by  her  penances.  In  his  hour  of  sickness  and  trouble  her  serv- 
ants sought  him  out,  teaching  him  by  her  exquisite  litanies  and  prayers 
to  place  his  reliance  on  God,  or  strengthening  him  for  the  trials  of  life 
by  the  example  of  the  holy  and  just.  Her  prayers  had  an  efficacy  to 
give  repose  to  the  soul  of  his  dead.  When  even  to  his  friends  his  life- 
less body  had  become  an  offense,  in  the  name  of  God  she  received  it  into 
her  consecrated  ground,  and  under  her  shadow  he  rested  till  the  great 
reckoning  day.  From  little  better  than  a  slave  she  raised  his  wife  to  be 
his  equal,  and,  forbidding  him  to  have  more  than  one,  met  her  recompense 
for  those  noble  deeds  in  a  firm  friend  at  every  fireside.  Discountenancing 
all  impure  love,  she  put  round  that  fireside  the  children  of  one  mother, 
and  made  that  mother  little  less  than  sacred  in  their  eyes.  In  ages  of 
lawlessness  and  rapine,  among  people  but  a  step  above  savages,  she  vin- 
dicated the  inviolability  of  her  precincts  against  the  hand  of  power,  and 
made  her  temples  a  refuge  and  sanctuary  for  the  despairing  and  oppress- 
ed. Truly  she  was  the  shadow  of  a  great  rock  in  many  a  weary  land ! 

The  civilization  of  the  European,  so  far  as  it  has  yet  advanced,  has 
been  accomplished  by  the  agency  of  many  different  causes,  foreign  and 
domestic ;  but  among  all  these,  the  institution  of  the  Christian  Church 
stands  pre-eminent  by  reason  of  the  moral  power  it  exerted,  its  duration, 
and  the  social  benefits  it  has  conferred. 


THE  SABBATH  DAY.  627 

Out  of  the  numberless  blessings  which  have  thus  been  conferred  on  our 
race  by  the  Church,  the  physiologist  may  be  permitted  to  se-  The  Sabbath 
lect  one  for  remark,  which,  in  an  eminent  manner,  has  con-  da^- 
duced  to  our  physical  and  moral  well-being.  It  is  the  institution  of  the 
Sabbath  day.  Not  that  this  originated  with,  or  is  peculiar  to  the  Chris- 
tian faith,  since,  as  is  known  to  all,  it  dates  from  the  remotest  times,  and 
was  directly  adopted  from  the  Hebrew  ceremonial.  Its  sanctification  and 
enforcement  by  the  Church  was  at  once  an  object  important  in  the  high- 
est degree  in  ecclesiastical  polity,  and  a  boon  to  all  classes  of  men ;  for 
in  whatever  position  of  life  we  may  be  placed,  it  is  needful  for  us  to  have 
an  opportunity  of  rest.  No  man  can  for  any  length  of  time  pursue  one 
avocation  or  one  train  of  thought  without  mental,  and,  therefore,  bodily 
injury — nay,  without  insanity.  The  constitution  of  the  brain  is  such 
that  it  must  have  its  time  of  repose.  Periodicity  is  stamped  Necessity  of 
upon  it.  Nor  is  it  enough  that  it  is  awake  and  in  action  by  Peri<>dsofrest. 
day,  and  in  the  silence  of  night  obtains  rest  and  repair;  that  same  perio- 
dicity which  belongs  to  it  as  a  whole,  belongs  to  all  its  constituent  parts. 
One  portion  of  it  can  not  be  called  into  incessant  activity  without  the 
risk  of  injury.  Its  different  regions,  devoted  to  different  functions,  must 
have  their  separate  times  of  rest.  The  excitement  of  one  part  must  be 
coincident  with  a  pause  in  the  action  of  another.  It  is  not  possible  for 
mental  equilibrium  to  be  maintained  with  one  idea,  or  one  monotonous 
mode  of  life.  There  is  a  necessity  even  for  men  of  great  intellectual  en- 
dowments, whose  minds  are  often  strained  to  the  utmost,  to  fall  back  on 
other  pursuits,  and  thus  it  will  always  be  that  one  seeks  refuge  in  the 
pleasures  of  quiet  country  life,  another  in  foreign  travel,  another  in  social 
amusements.  Pitt  sought  a  relaxation  from  the  cares  of  politics  in  the 
excitement  of  the  chase ;  Davy  found  a  relief  and  consolation  in  the  rod 
and  line ;  and  among  men  whose  lot  is  cast  in  the  lowliest  condition,  whose 
hard  destiny  it  is  to  spend  their  whole  lives  in  the  pursuit  of  their  daily 
bread,  with  one  train  of  thought  and  one  unvarying  course  of  events,  the 
same  principle  imperiously  applies.  It  is  often  said  that  the  pleasures 
of  religion  are  wholly  prospective,  and  to  be  realized  only  in  another 
world ;  but  in  this  there  is  a  mistake,  for  those  consolations  commence 
even  here,  and  temper  the  bitterness  of  fate.  The  virtuous  laborer,  though 
he  may  be  ground  down  with  the  oppressions  of  his  social  condition,  is 
not  without  his  relief:  at  the  anvil,  the  loom,  or  even  the  bottom  of  the 
mine,  he  is  leading  a  double  existence — the  miseries  of  the  body  find  a 
contrast  in  the  calm  of  the  soul,  the  warfare  without  is  compensated  by 
the  peace  within,  the  dark  night  of  life  here  serves  only  to  brighten  the 
glories  of  the  prospect  beyond.  Hope  is  the  daughter  of  Despair.  And 
thus  a  kind  Providence  so  overrules  events  that  it  matters  not  in  what 
station  we  may  be,  wealthy  or  poor,  intellectual  or  lowly,  a  refuge  is  al- 


628  PUBLIC   WORSHIP. 

ways  at  hand,  and  the  mind,  worn  out  with  one  thing,  turns  to  another, 
and  its  physical  excitement  is  followed  by  physical  repose. 

By  the  enforcement  of  the  observance  of  the  Sabbath  the  Church  gave 
Influence  of  effect  to  this  providential  system  of  physical  and  mental  re- 
public worship.  Jie£  J  have  already  said  that  her  chief  strength  lay  in  this, 
that  she  concerned  herself  with  the  common  man,  who  never  in  the 
world's  history  before  had  had  any  to  watch  over  or  to  care  for  him. 
She  humanized  him  by  the  devotional  solemnities  of  a  sacred  day — a 
day  of  entire  relief  from  toil.  Ignorant  and  rude  though  he  might  be, 
it  was  not  possible  for  him  to  enter  her  hoary  temples  without  being 
made  a  better  man.  The  atmosphere  of  rest,  the  twilight  streaming 
through  the  painted  windows,  the  prayer  in  an  unknown  tongue,  the  slow 
chanting  of  old  hymns,  or  the  swelling  forth  of  those  noble  strains  of 
music,  which,  once  heard,  are  graven  in  remembrance  forever — these  she 
had  made,  with  more  than  worldly  wisdom,  the  elements  or  incidents  of 
public  worship.  She  gratified  the  manly  sense  by  asserting  before  her 
altar  the  equality  of  all  men,  by  making  the  vain  and  transitory  grada- 
tions of  society  disappear,  and  by  teaching  the  rich  and  the  poor,  the 
great  and  the  humble,  their  common  dependence  on  the  mercy  of  God. 
Under  her  powerful  influence,  inarticulate  Nature,  as  if  spellbound,  seem- 
ed to  acquiesce  in  the  tranquillity  of  the  Sabbath  day,  and  to  assume 
an  air  of  rest.  In  the  cottage  they  rose  at  a  later  hour.  The  father 
cleansed  himself  with  more  than  usual  care,  and,  if  it  was  the  custom 
of  his  country,  shaved  his  face,  perhaps  sadly  neglected  in  the  interven- 
ing week,  and  dressed  himself  in  his  better  clothing.  His  honest  pride 
found  a  gratification  in  the  neatness  of  his  wife  and  children.  His  table 
was  more  bountifully  supplied,  his  heart  humanized  by  the  grateful  re- 
lief from  labor,  and  the  society  and  converse  of  those  dearest  to  him. 
Physically  and  mentally  he  rests,  and  by  that  rest  is  enabled  to  sustain 
the  cares  of  a  life  of  toil.  It  is  not  without  a  reason  which  we  may  turn 
to  our  profit,  that  the  Scriptures  have  placed  upon  lasting  record  that 
the  Great  Head  of  the  Church  has  taught  us  both  by  precept  and  personal 
example  how  to  use  this  day ;  and  that,  for  the  sake  of  the  many  gen- 
erations of  laboring  and  weary  men  who  were  to  follow  him,  he  inflexibly 
resisted  every  attempt  at  encroachment  upon  it  by  the  grim  bigots  and 
hypocrites  of  his  times. 

Though  Kome  did  little  for  Europe  in  the  production  of  knowledge, 
The  civil  s^e  ^us  serve<^  *ts  interests  well  in  the  most  vital  respects. 
She  gave  it  her  system  of  law  and  her  religion.  With  the 
introduction  of  Roman  usages  among  barbarians  came  the  Roman  law, 
modifying  or  abrogating  the  existent  imperfect  polities.  To  a  consider- 
able extent,  its  spread  was  due  to  the  influence  of  the  ecclesiastics  and 
the  wants  of  the  rising  municipalities. 


INFLUENCE    OF   THE   ARABS.  629 

The  influence  exerted  by  the  Koman  empire  on  the  social  condition  of 
Europe  in  the  two  particulars  to  which  reference  has  been  Influence  of the 
made,  the  introduction  of  the  civil  law,  and  the  establish-  Mohammedans 
ment  of  the  Christian  Church,  occurred  in  the'  period  of  its  ° 
decline,  and  was  therefore  contemporaneous  with  the  spread  of  Moham- 
medanism through  the  north  of  Africa,  and  the  occupancy  of  Spain  by 
the  Arabs.  To  a  very  considerable  degree,  the  practical  character  which 
European  thought  has  exhibited  in  later  centuries  is  to  be  attributed  to 
the  Arabians,  who  have  justly  been  termed  the  founders  of  physical  sci- 
ence ;  for  though,  through  them,  the  literature  of  Greece  was  intro- 
duced into  Western  Europe,  the  writings  of  Aristotle,  for  example,  being 
made  known  through  an  Arabic  translation,  they  imparted  to  what  they 
thus  gave  their  own  particular  impress.  Being  the  first  founders  of  or- 
ganized institutions  for  the  cultivation  of  medical  pursuits,  answering 
completely  to  our  modern  medical  colleges,  they  attached  to  those  pro- 
fessional studies  their  own  peculiar  methods.  It  was  therefore  in  this 
way  that  botany  and  chemistry  were  particularly  cultivated,  be-  The  Arab 
cause  they  were  regarded  as  the  foundation  of  Materia  Medica.  schools. 
Humboldt  remarks,  that  while  the  Europeans  have  been  disposed  to  con- 
nect the  physical  sciences  with  theology,  the  Arabians  connected  them 
with  medicine,  and  that  through  their  medical  colleges  they  ruled  the 
Christian  schools,  who  looked  up  to  Avicenna  and  Averroes  as  the  great 
authorities  on  these  subjects.  The  most  important  applications  of  the 
mathematical  sciences  to  the  purposes  of  life  were  made  by  the  Arabs. 
Of  this  it  is  sufficient  to  mention  the  introduction  of  the  notation  of  arith- 
metic and  many  instruments  of  navigation,  the  former  not  only  fur- 
nishing an  invaluable  aid  in  the  computations  required  by  the  wants  of 
a  commerce  which  reached  from  the  north  of  Europe  to  Madagascar,  and 
from  the  Atlantic  islands  to  China,  but,  what  was  of  even  more  import- 
ance, in  the  progress  of  mathematical  science  itself,  the  latter  through  the 
aid  afforded  in  astronomical  observations  permitting  the  successful  ac- 
complishment of  voyages  in  seas  which  even  to  that  time  had  been  little 
frequented. 

It  would  extend  this  chapter  unduly  if  we  were  to  enter  into  any  de- 
tail of  the  special  contributions  of  the  Arabs  to  the  stock  of  Eu-  Arab  discov- 
ropean  knowledge.  It  may,  however,  be  briefly  remarked,  that  eries- 
we  owe  to  them  our  system  of  universal  arithmetic,  and  even  the  title 
under  which  it  now  passes,  algebra.  Their  discovery  of  the  strong  acids, 
nitric,  sulphuric,  and  also  aqua  regia,  constitutes  an  epoch  in  chemistry. 
The  cultivation  of  that  science  also  was  stimulated  in  no  small  degree 
by  their  attempts  at  the  transmutation  of  the  baser  metals  into  gold,  and 
the  discovery  of  the  means  of  indefinitely  prolonging  life — the  philoso- 
pher's stone  and  the  elixir  vita?.  In  the  science  of  optics,  the  work  of 


(330  THE    CRUSADES. 

Alhazen  on  refraction  demonstrates  their  cultivation  of  the  methods  of 
physical  experiment  and  observation,  and  their  application  of  the  pendu- 
lum to  the  measurement  of  time  is  even  yet  acknowledged  to  be  the  most 
perfect  contrivance  for  that  purpose. 

In  estimating  the  value  of  the  influence  which  the  Mohammedans  ex- 
erted upon  the  European  mind,  we  recognize  its  specific  similarity  to 
that  which,  more  than  a  thousand  years  before,  had  been  communicated 
from  the  schools  of  Egypt  under  its  Macedonian  kings,  and  even,  still 
centuries  before  that,  at  the  time  of  the  opening  of  the  Egyptian  ports. 
In  all  three  cases  the  tendency  imparted  was  to  the  cultivation  of  the 
physical  sciences,  then  in  their  infancy,  and  thereby  to  the  increase  of 
the  material  power  of  the  race.  In  a  very  short  time,  inventions  which 
have  been  of  the  utmost  importance  made  their  appearance,  such  as  gun- 
powder, the  mariner's  compass,  and  various  optical  instruments.  It  is 
of  no  moment  whether  these  were  introduced  by  the  enterprise  of  the 
Arabs  from  Asia  or  whether  they  were  of  indigenous  origin ;  there  can 
be  no  doubt  that  the  intellect  of  Europe  had  reached  that  peculiar  phase, 
and  the  tendency  of  thought  was  in  that  particular  direction  that,  even 
if  these  discoveries  had  not  been  communicated  from  abroad,  they  would 
very  soon  have  been  made  at  home. 

The  Mohammedan  attacks  on  Europe  were  retaliated  by  the  Crusades. 
These  strange  wars,  into  which  the  white  race  plunged,  were 

The  Crusades.    .  -,   -,         ,       -A  111 

instigated  by  the  Koman  government  toward  the  close  ot 
the  eleventh  century,  and  were  followed  by  consequences  which  their  pro- 
jectors never  expected.  They  precipitated  barbarian  Europe  upon  Asia, 
under  the  pretense  of  rescuing  the  Savior's  tomb  from  the  infidel,  but  in 
reality  to  keep  back  the  threatened  tide  of  Saracenic  invasion,  and  to  di- 
vert from  Italy  the  restless  military  spirit  that  was  every  where  engen- 
dering. No  other  motive  than  the  one  thus  ostensibly  put  forth  could 
have  brought  the  ferociously  independent  hordes  of  Europe  to  act  to- 
gether. It  had  been  well  if,  in  ancient  times,  the  emperors  had  been  in 
possession  of  so  useful  a  device ;  it  might  have  saved  the  city  from  some 
sieges  and  sacks.  As  it  was,  the  turbulent  stream  was  thrown  upon  the 
Byzantine  monarchs  to  their  utter  perplexity.  The  Saracens  received 
it  with  amazement.  The  ostensible  causes  which  had  set  in  motion  such 
a  countless  rabble  of  stupid  barbarians  were  absolutely  incomprehensi- 
ble by  them.  In  their  invasions  of  Europe  they  had  carried  the  light 
of  such  science  as  they  possessed,  but  in  this  counter  invasion  of  Asia 
they  were  repaid  with  the  most  besotted  ignorance. 

The  Crusaders  found  that  the  infidel  they  had  come  so  far  to  encoun- 
influeaceofthe  ter  w^nout  provocation  was  valiant  and  polished,  in  many 
Crusades  ou      cases  merciful  and  just.     Their  ideas  of  the  Asiatics  under- 
went a  great  change  after  they  had  been  in  contact  with 


EFFECTS  OF  THE  CRUSADES.  631 

them  for  a  time.  Those  who  lived  to  return  to  their  homes  from  the 
successive  expeditions  spread  abroad  a  more  enlarged  and  correct  con- 
ception of  Oriental  countries,  events,  and  men,  the  influence  of  which 
was  not  lost  to  civilization.  In  his  imprisonment  in  the  fortress  of 
Dierstein,  the  lion-hearted  Richard  of  England  doubtless  reflected  that 
there  was  more  honor  in  the  infidel  Saladin  than  in  many  a  Christian 
king.  It  has  not  escaped  the  observation  of  historians  that  the  frequent 
communication  which  these  events  established  between  all  parts  of  Eu- 
rope and  the  Italian  court  served  often  to  disturb  the  sentiment  of  piety. 
The  visitors  at  Rome  saw  things  which  had  been  better  concealed.  Their 
unaffected  simplicity  was  shocked  by  the  dissipation  and  immoralities  in 
high  places.  They  carried  the  shameful  story  to  their  homes. 

Among  the  unexpected  and  lasting  advantages  arising  from  the  Cru- 
sades, not  one  of  which  had  been  contemplated  by  the  Ital-  Advantages 
ian  court,  may  be  enumerated  more  enlarged  and  liberal  views  derived  from 
of  foreign  nations,  and  the  importation  of  Asiatic  discoveries. 
From  the  remote  parts  of  that  continent  embassadors  came  to  Italy,  and 
enterprising  European  travelers,  like  Marco  Polo,  wandered  in  return  all 
over  it.  In  this  manner  the  knowledge  of  the  mariner's  compass  was 
obtained.  From  having  learned  to  employ  their  ships  in  warlike  expe- 
ditions, the  Western  nations  were  induced  to  enter  on  that  career  of  mar- 
itime commerce  which  soon  led  them  to  the  discovery  of  America  and 
the  doubling  of  the  Cape  of  Good  Hope,  and  which,  in  these  times,  con- 
stitutes the  chief  feature  of  their  life*.  Trade,  which  until  then  had  been 
overland  or  terrestrial,  became  maritime — a  change  important  to  the  last 
degree,  since  it  eventually  gave  rise  to  the  prodigious  development  of 
manufacturing  industry.  Heavy  masses  of  goods  can  never  be  trans- 
ported by  caravans,  though  they  can  easily  in  ships.  The  geographical 
value  of  countries  was  changed.  Egypt,  for  instance,  lost  her  position, 
not  to  be  recovered  again  until  the  invention  of  the  locomotive,  which 
will  restore  land-transport  to  its  former  state.  Wealth  poured  into  the 
maritime  states,  and  markets  were  sought  for  all  over  the  globe.  More- 
over, the  separate  principalities  and  kingdoms  were  taught  to  act  in  uni- 
son, and  the  idea  of  Europe — united  Europe — was  made  manifest.  As 
a  present  advantage  was  realized  the  downfall  of  the  feudal  system,  and, 
as  a  direct  consequence  thereof,  a  redistribution  of  the  population.  To 
this  system,  in  its  flourishing  period,  some  have  been  disposed  to  impute 
many  benefits — that  it  originated  our  domestic  manners,  gave  birth  to 
the  sentiment  of  loyalty  and  honor,  cherished  independence,  and  elevated 
the  female  sex ;  but  these  are  misconceptions  or  exaggerations.  In  the 
last  particular,  the  advancement  of  women,  the  merit  is  strictly  due  to 
the  Church ;  for,  had  there  been  no  other  reason,  the  universal  preva- 
lence of  Mariolatry  throughout  Christendom,  by  diffusing  a  most  accept- 


632  SPANISH   DISCOVERY   OF   AMERICA. 

able  and  even  adorable  image  of  female  loveliness  and  virtue,  would  have 
led  to  that  result. 

But  far  exceeding  the  Crusades  in  effect,  more  distinct  in  its  origin, 
Discover  of  since  ^  directly  resulted. from  the  tone  of  thought  which  the 
America  by  Arabs  had  introduced,  lasting  in  the  influence  that  it  has  ex- 

the  Spaniards.   ^^  and  ^  forever  exert   on   the   destinies   Qf  ^  wjlite 

race,  was  the  discovery  of  America  by  the  Spaniards  in  1492.  This  con- 
tinent, four  hundred  years  before,  had  been  visited  repeatedly  by  the  Ice- 
landers and  Norwegians  ;  but  the  shores  they  discovered  being  less  hos- 
pitable and  less  tempting,  their  expeditions  unsupported  by  a  powerful 
home  government,  and  the  results  little  attractive,  the  very  remembrance 
of  them  seems  almost  to  have  passed  away.  Had  it  not  been  for  the 
magnetic  needle,  and  other  instruments  of  navigation  introduced  from  the 
East,  the  passage  of  the  tropical  Atlantic  could  never  have  been  accom- 
plished, and  probably  would  never  have  been  attempted.  Moreover,  we 
must  not  overlook  the  fact  that  the  rapid  conquests  of  the  Saracens,  and 
even  the  Crusades  themselves,  had  introduced  a  largeness  of  conception, 
and  had  familiarized  the  public  mind  with  undertakings  to  be  accom- 
plished in  regions  that  were  very  remote.  The  successful  return  of  Co- 
lumbus from  his  first  voyage  found  all  Europe  ready  to  rush  into  West- 
ern enterprises,  and  this  event  may  be  truly  regarded  as  a  grand  epoch 
in  the  history  of  the  white  race,  since  it  more  than  quadrupled  the  geo- 
graphical surface  over  which  they  might  spread,  and  presented  to.  their 
unmolested  occupation  climates  from  the  equator  to  the  extreme  north 
and  south. 

In  the  prodigious  emigration  that  ensued,  Spain  led  the  way,  and  did 
Colonial  em-  so  to  her  ruin.  In  vain  she  received  and  scattered  over  Eu- 
pire  of  Spain.  r0pe  the  wealth  of  Mexico  and  Peru ;  she  gave  in  exchange 
for  it  what  was  to  her  of  infinitely  more  value — the  most  enterprising 
and  bravest  of  her  people.  The  drain  of  this  class  produced  an  effect 
from  which  she  has  never  recovered.  It  left  her  without  energy  and  im- 
becile. In  vain  she  founded  a  greater,  and,  for  the  time,  more  prosperous 
colonial  empire  than  history  has  ever  recorded,  carrying  her  influences 
through  a  large  part  of  South  and  much  of  North  America,  from  the  At- 
lantic to  the  Pacific  Ocean.  Her  emigrants,  unable  to  withstand  the  in- 
fluences of  a  tropical  climate,  and  intermarriages  and  connections  with 
the  native  races  among  whom  they  were  thrown,  soon  lost  the  enterprise 
that  had  once  distinguished  them,  and  the  descendants  of  the  Spaniard 
in  America  exemplify  at  this  day  the  universal  imbecility  that  is  exhib- 
ited in  the  mother  country. 

In  her  pursuit  of  the  wealth  of  America  Spain  was  a  fearful  oppress- 
The  fan  of  the  or.  Bartholomew  de  las  Casas,  the  Bishop  of  Chiapa,  to  use 
Spanish  power.  kjs  QWn  expression,  charged  her  "before  the  tribunal  of  the 


POPULAR  PHILOSOPHICAL   BELIEF.  633 

Universe,"  with  destroying  more  than  fifteen  millions  of  natives  during 
his  time.  "  The  acrimony  of  his  style  was  complained  of,  but  the  fact 
was  never  denied."  No  nation  can  practice  such  atrocities  with  impu- 
nity. The  day  of  reckoning  may  be  a  little  postponed,  but  it  brings  its 
inexorable  verdict  in  the  end.  The  broad  hand  of  an  overruling  Provi- 
dence is  at  last  plainly  discovered,  imposing  with  an  unerring  justice  the 
penalty  of  national  crime.  There  is  no  need  for  God  to  hasten,  he  has 
the  centuries  and  eternity  to  work  in.  Even  now,  is  not  the  Spaniard  in 
the  hands  of  an  avenger  for  the  Indian  blood  that  cries  for  retribution 
from  the  silver  mines  of  Mexico  ?  For  the  failings  of  the  individual 
there  is  mercy,  but  in  the  ways  of  eternal  justice  no  mediator  is  provided 
for  the  crimes  of  society.  There  is  an  inflexible  recompense  of  good  for 
good  and  evil  for  evil. 

The  step  which  the  intellect  of  the  white  man  has  made  since  the  Ref- 
ormation is  very  strikingly  discerned  by  comparing  the  nat-  Thelatermen_ 
ural  philosophy  of  the  fifteenth  with  that  of  the  nineteenth  cen-  tai  changes  in 
tury.  Its  passage  to  its  present  condition  has  been  mark- 
ed by  a  continual  casting  away  of  the  marvelous.  It  is  almost  impossi- 
ble for  us  now  to  realize  the  fictions  which  occupied  the  minds  of  our 
predecessors.  To  pejietrate  "the  secrets  of  nature"  is  with  us  a  meta- 
phorical expression ;  with  them,  a  portentous  and  solemn  reality,  most 
readily  accomplished  by  the  help  of  familiars  and  imps,  whose  services 
might  be  secured  by  forbidden  enchantments.  The  laboratory  of  an  al- 
chemist was  ill  furnished  which  did  not  possess  in  the  shape  of  an  un- 
gainly and  deformed  dwarf  such  an  aid,  and  who,  if  not  the  incarnation 
of  a  devil,  was  at  least  possessed  by  one.  Operations  for  the  discovery 
of  the  philosopher's  stone,  the  powder  of  projection,  and  elixir  of  life, 
were  necessarily  commenced  by  exorcism,  invocations,  and  a  favorable 
aspect  of  astrological  combinations.  There  were  seven  planets,  and  also 
seven  metals,  and  the  guiding  spirits  which  resided  in  the  former  exer- 
cised their  influence  over  the  latter,  communicating  to  them  their  specific 
virtues.  The  expressions  have  lost  their  significance,  though  they  have 
descended  to'  our  times,  when  we  call  a  certain  metal  mercury,  and  a  salt 
lunar  caustic. 

As  Mr.  D'Israeli,  in  bis  "  Curiosities  of  Literature,"  remarks,  whoever 
had  been  a  witness  of  the  miracles  of  these  philosophers  might  well  be 
prepared  to  believe  any  of  their  declarations.  He  who  had  visited  the 
dark  chamber  of  Baptista  Porta,  and  seen  with  his  own  eyes  its  fairy 
but  inverted  landscapes,  its  fields,  and  rocks,  and  rivers,  and  the  moving 
forms  of  men  and  animals  in  their  proper  colors  and  indescribable  charm 
of  light  and  shade,  the  clouds  and  sky,  the  magical  spectres  of  things 
which  the  fingers  could  not  grasp,  a  perfect  but  artificial  day-dream,  might 
surely  feel  justified  in  also  believing  in  the  enchanted  mirror  upon  which, 


634  DISAPPEARANCE   OF   CREDULITY. 

if  a  man  looked,  he  would  find  reflected  all  the  future  events  of  his  life. 
He  who  had  seen  the  phantasmagoria  cast  upon  smoke  in  these  myste- 
rious laboratories,  now  so  little  that  the  eye  could  scarcely  discern  their 
form,  and  now  expanding  to  a  gigantic  stature  and  rushing  forth,  was 
duly  prepared  to  credit  the  legends  of  brazen  men  who  could  speak  and 
even  prophesy,  nay,  whose  limbs  would  continue  to  grow  unless  the  de- 
mon that  possessed  them  was  cast  out.  A  vial  of  that  which  we  call 
ammonia,  the  mere  smelling  of  which  can  recall  one  from  a  swoon,  was 
a  very  fair  earnest  of  the  elixir  of  life.  JSTo  prodigy  was  too  great  to  be 
believed.  As  in  dreams,  nothing  was  too  impossible,  nothing  too  con- 
tradictory. Men  who  could  make  themselves  invisible  even  without  the 
romantic  aid  of  a  ring ;  incombustible  sages  who  could  wash  themselves 
in  melted  copper,  and  sit  at  their  ease  in  flaming  straw ;  alchemists  in 
possession  of  the  philosopher's  stone,  but  their  stomachs  as  empty  as  their 
bellows  ;  monks  carrying  about  fairies  shut  up  in  glass  vials,  into  which 
Gr  d  l  disa  they  had  been  decoyed  by  distilled  dew ;  salamanders  which 
pearance  of  ere-  had  been  engendered  in  a  fire  maintained  without  ever  go- 
ing out  for  forty  years ;  a  rain  in  Egypt  in  which  there  fell 
multitudes  of  little  men  of  less  than  one  span,  clothed  in  black  garments, 
and  with  mitres  like  bishops :  these  were  all  facts  in  the  philosophy  of 
that  day.  The  explosions  and  choke-damp  of  mines  were  not  disentan- 
gled from  spectres  and  faces  of  abominable  appearance  which  had  been 
seen  in  those  subterranean  solitudes  by  numberless  witnesses  until  the 
dawn  of  pneumatic  chemistry.  The  palingenesis,  or  resurrection  of  roses 
and  apparitions  of  flowers,  so  acceptable  in  doctrinal  theology,  continued 
to  be  received  until  crystallography  was  cultivated.  These  wonders  have 
all  passed  away. 

The  character  which  marks  this  change  is  the  gradual  dropping  of  mys- 
tery and  the  supernatural.  The  same  career  is  followed  from  infancy  to 
maturity,  both  in  the  individual  and  in  society. 

It  is  not  necessary  to  pursue  any  further  this  historical  outline.  It 
would  bring  us  to  events  which  can  scarcely  be  spoken  of  with  correct- 
ness and  impartiality,  on  account  of  their  nearness  to  our  own  times. 
Here,  therefore,  we  may  pause,  to  collect  such  inferences  and  present  such 
reflections  as  the  facts  we  have  offered  suggest. 

It  may,  then,  be  observed,  that  the  old  white  inhabitants  of  Europe 
Ph  siolo  ical  were  no*  a^e  *°  commence  their  civilization  from  their  own 
change  of  Eu-  interior  resources,  but  were  thrown  into  that  career  by  the  ex- 
ample and  aid  of  a  more  southern  and  darker  people,  whose 
climate  was  more  favorable.  The  artificial  change  which  spread  by  de- 
grees over  Europe,  through  the  introduction  of  more  comfortable  modes 
of  life,  at  last  compensated  for  the  natural  climate  defect,  and  the  Euro- 
pean entered  on  the  course  of  advancement,  undergoing,  as  we  have  seen 
in  the  last  chapter,  a  physical  as  well  as  a  mental  change. 


EFFECT  OF  MOHAMMEDANISM  OX  EUROPE.          635 

Contemporaneous  with  the  commencement  of  this  physiological  and 
psychical  change  was  the  introduction  of  a  method  of  record  Eesult  of  the 
by  writing,  which  at  once  aided,  in  the  most  marked  manner,  introduction  of 
the  dissemination  of  this  improving  condition,  especially  by  * 
leading  to  the  consolidation  of  society  through  the  introduction  of  durable 
systems  of  law.  By  this,  the  influence  of  men  and  of  generations  was 
indefinitely  extended.  The  opinions  and  thoughts  of  those  times  have 
actually,  in  many  instances,  descended  to  us.  Elsewhere  we  have  dwelt 
on  the  fact  that  these  effects  in  the  progress  of  humanity  are  foreshadow- 
ed and  illustrated  in  the  course  of  individual  development.  A  high  psy- 
chical condition  demands  as  its  essential,  both  in  the  individual  and  in 
the  race,  a  mechanism  of  registry. 

From  the  preceding  imperfect  narration  we  may  moreover  gather  that 
the  progress  of  civilization  in  Europe  has  not  been  in  the  way  Centre  of intel- 
of  a  diffusion  from  a  central  point,  but  that  there  has  been  a  lect  of  Eur°Pe- 
shifting  of  the  centre  of  intellect.  For  a  length  of  time  it  was  in  Greece ; 
then  it  passed  to  Italy ;  in  our  times  it  is  still  more  to  the  west.  In  a 
philosophical  respect,  the  result  of  Mohammedanism  on  Europe  has  been, 
through  the  introduction  'of  physical  science  by  the  Arabians,  to  coalesce 
the  centre  of  intellect  and  the  centre  of  force.  Henceforth  upon  that 
continent  physical  power  must  be  subordinate  to  intellectual. 

In  this  we  see  what  is  the  true  interpretation  of  the  influence  which 
Mohammedanism  has  exerted  on  Europe — an  influence  which,  Effect  of  Mo_ 
though  popularly,  is  very  unworthily  represented  as  an  oc-  hammedanism 

?•          £o      •     r          /  •  /^  *rt          on  the  centre 

cupation  of  Spam  for  a  few  centuries  and  the  capture  of  Con-  Of  intellect  of 
stantinople.  In  truth,  it  was  of  a  far  higher  and  very  dif-  Eur°Pe- 
ferent  order.  The  Koran  of  the  Arabians  failed  to  make  its  way  through 
Europe,  but  it  was  very  different  with  the  physical  science  of  the  Arabi- 
ans. Its  spread  was  the  true  foundation  of  modern  national  power,  for 
it  at  once  occupied  itself  with  the  development  of  material  resources  and 
the  introduction  of  useful  inventions.  The  manner  of  thought  it  engen- 
dered lies  really  at  the  basis  of  the  great  intellectual  controversy  of  our 
times.  The  translation  of  the  centre  of  intellect  from  Italy  to  the  West 
is  the  legitimate  issue  of  the  Moorish  invasion  of  Spain. 

As  regards  that  propensity  to  the  decomposition  of  every  thing  into 
its  constituent  elements  which  is  the  tendency  of  the  Euro-  Eesult  of  the 
pean,  though  doubtless  it  has  its  disadvantages,  we  are  not  enc^n^Eu" 
to  suppose  that  it  leads  of  necessity  to  an  intellectual  chaos,  ropean  mind. 
Those  authors  who  view  with  dismay  our  present  state,  who  represent 
us  as  though,  both  in  polity  and  religion,  we  were  crumbling  to  pieces, 
and  that  the  multiplicity  of  opinions  and  sects,  which  are  ever  on  the 
increase,  is  the  precursor  of  a  universal  anarchy,  have  never  duly  con- 
sidered that  out  of  such  a  state  it  is  possible  in.  an  instant  for  fixed 


636  CONDITION   OF   EUROPEAN   IMPROVEMENT. 

principles  of  order  to  emerge,  and  this  not  by  any  process  of  compression 
or  suppression,  but  spontaneously  in  the  natural  course  of  events.  In 
the  outset  of  this  brief  historical  description  I  have  alluded  to  the  adop- 
tion of  alphabetic  writing  in  Europe  as  a  signal  illustration  of  the  mental 
peculiarity  of  the  inhabitants ;  this  may  also  serve  to  make  clear  the 
paradoxical  assertion  that  systems  founded  on  indefinite  subdivision 
may  suddenly  free  themselves  from  complexity  and  become  simple  and 
perspicuous.  On  a  superficial  consideration  of  the  thing,  one  might  im- 
agine that  to  decompose  articulate  sounds  into  their  constituent  syllables, 
with  a  view  of  representing  those  syllables  by  symbols,  would  be  at- 
tended with  a  prodigious  complication,  and  that  such  is  the  case  the  Chi- 
nese have  found,  who  have  pursued  this  plan  in  its  details  until  it  is 
said  that  their  alphabet  contains  80,000  letters  ;  but  still  more  would  it 
be  supposed  that  if  those  syllables  were  in  their  turn  decomposed  into 
their  constituent  parts,  the  required  elements  would  be  utterly  unman- 
ageable by  reason  of  their  number,  and  the  art  of  writing  utterly  imprac- 
ticable ;  yet  do  we  not  find,  on  the  contrary — and  it  may  be  an  instruct- 
ive lesson  to  us — that  when  the  decomposition  is  thus  pushed  to  its  ex- 
treme, instead  of  myriads  of  characters  b$ing  required,  as  we  might  have 
plausibly  expected,  an  alphabet  of  20  or  30  letters  is  all  we  want  ?  The 
state  of  opinion  in  Europe  is  illustrated  by  the  state  of  writing  in  China. 

In  view  of  the  facts  presented  in  this  and  the  foregoing  chapter,  we 
may  come  to  the  general  conclusion  that  the  extremes  of  humanity,  which 
are  represented  by  a  prognathous  aspect  and  by  a  complexion  either  very 
dark  or  very  fair,  are  equally  unfavorable  to  intellect,  which  reaches  its 
greatest  perfection  in  the  intermediate  phase ;  that,  even  in  the  condition 
which  was  presented  by  the  inhabitants  of  Europe  three  thousand  years 
ago,  no  advance  in  civilization  was  possible,  save  by  first  accomplishing 
Conditions  of  an  ^solute  physical  change  in  their  constitution  through 
European  im-  modifications  in  their  habits  of  life  equivalent  to  a  true  cli- 
3nt*  mate  change — a  preparation  for  a  higher  mental  development 
by  an  amelioration  of  their  condition  of  life. 

The  civilization  of  the  European  could  never  have  been  accomplished 
save  by  preparing  the  way  through  such  a  physical  change.  It  followed 
that  change  in  the  manner  that  effect  follows  its  cause.  Its  incident  was 
the  transformation  of  the  fair  race  which  then  occupied  all  Europe  to  an- 
other of  a  darker  hue ;  the  extinction  of  the  disappearing  people  not  be- 
ing accomplished  by  such  means  as  an  extermination,  after  the  manner 
in  which  the  North  American  Indian  is  dying  out,  but  by  a  slow  and  true 
metamorphosis  into  another  form. 

Advance  in  civilization  takes  place  during  such  a  metamorphosis.  Asia, 
Stationary  con-  which,  at  an  early  period,  must  have  exhibited  a  mental  de- 

tion  of  Asia,    yelopment  of  great  rapidity,  has  long  ago  become  stationary. 


ADVANTAGES   OF  THE   ANALYTICAL  MIND.  637 

In  her  physical  life  there  is  no  change,  and  hence  none  in  her  intellect- 
ual. Her  wandering  central  tribes  encamp  on  the  steppes  in  the  same 
felt  huts  that  their  ancestors  did  two  thousand  years  ago  ;  her  southern 
people  never  vary  their  customs.  That  which,  in  a  philosophical  respect, 
is  the  most  important  condition,  domestic  economy,  has  undergone  no 
kind  of  modification. 

But  with  us,  how  different !  The  hardships  of  life  have  to  a  very  great 
extent  been  removed,  and  we  are  familiar  with  a  degree  of  comfort  to 
which  our  predecessors  were  wholly  strangers.  Not  that  we  have  been 
freed  from  all  trials ;  it  has  only  been  an  exchange  of  bodily  sufferings 
for  mental  anxieties.  Our  higher  condition  has  created  new  wants  and 
new  sources  of  pain. 

With  the  transformations  through  which,  as  a  race,  we  have  passed, 
and  with  the  assumption  of  that  analytical  mental  character  Advantages 
to  which  I  have  referred,  there  has  been  gained  a  capability  arising  from  an 

<»  •    i   *»    • .  i  -!•{••  1    j  i         /*  c  •  analytical  and 

oi  indefinitely  modifying  our  state,  and,  therefore,  ot  improv-  mental  consti- 
ing  it.  It  is  this  which  pre-eminently  distinguishes  the  Eu-  tution- 
ropean ;  that  whatever  scientific  discovery  he  makes,  or  whatever  inven- 
tion occurs  to  him,  he  forthwith  applies  it  to  economic  advantage,  and  is 
thereby  perpetually  impressing  a  change  on  his  own  state.  In  this  re- 
spect, even  a  single  generation  often  suffices  to  show  the  advances  which 
are  made.  We  have  only  to  recall  the  greatly  improved  means  of  loco- 
motion ;  the  instantaneous  transmission  of  intelligence  through  many 
thousand  miles ;  the  development  of  industrial  art,  and  the  rendering 
available  mechanical  powers  for  many  new  purposes,  which  have  been 
achieved  in  less  than  a  single  century.  Nor  does  there  seem  to  be  any 
possible  limit  to  human  advance  in  this  path. 

Since  thus  the  mind  of  the  European  is  essentially  analytic,  his  ad- 
vance in  civilization,  as  it  were  in  a  geometrical  progression,  is  the  neces- 
sary consequence  thereof.  If  we  examine  his  career  in  subordinate  par- 
ticulars, it  illustrates  equally  his  mental  physiognomy ;  it  is  the  same 
whether  we  look  to  his  passage  in  philosophy,  science,  politics,  or  religion. 
If  I  may  be  permitted  without  offense  so  to  say,  his  divergence  from  a 
single  form  of  faith,  the  springing  up  of  those  numberless  denominations 
and  sects  which  constitute  the  most  observable  feature  of  his  present  re- 
ligious state,  is  a  result  which  he  can  not  help,  for  it  is  the  consequence 
of  his  organization.  Things  which  were  possible  in  the  eighth  century 
had  become  impossible  in  the  new  state  of  the  sixteenth.  And  so,  too, 
it  is  in  his  political  relations. 

Herein  consists  the  superiority  of  the  analytical  over  the  synthetical 
mind.  To  the  work  of  him  who  pulls  to  pieces  there  is  no  end,  but  he 
who  puts  things  together  comes  to  an  end  of  his  task. 


INDEX. 


ABDUCENTES,  334. 

Aberration,  chromatic  and  spherical,  386. 

Abrupt  and  gradual  impressions,  483. 

Absorbed  material,  course  of,  109. 

ABSORPTION,  forces  of,  110 ;  by  blood-vessels, 
49,  84,  102  ;  nutritive,  84 ;  double  mecha- 
nism for,  84 ;  in  plants,  86 ;  summary  of, 
108  ;  by  lacteals,  84,  86  ;  by  lungs,  163 ; 
by  general  surface,  98 ;  by  skin,  98,  241 ; 
two  kinds  of,  86 ;  interstitial,  98  ;  selecting 
power  in,  99. 

Abyssinian,  577. 

Acid,  hydrochloric,  use  of,  52. 

Activity  of  the  brain  depends  on  arterializa- 
tion,  326. 

Affinity  for  tissues  the  cause  of  circulation, 
133,  147. 

Africa,  influence  of  Europe  and  Asia  on,  593 ; 
prospective  civilization  of,  597  ;  inhabit- 
ants of,  577. 

Agassiz  on  origin  of  nations,  568. 

Age,  influence  of,  61,  172  ;  old,  545. 

Agents,  external,  influence  of,  on  man,  567. 

Agony,  final,  562. 

Air,  introduction  of,  160;  expired  per  min- 
ute, 168  :  passages,  evaporation  from,  186. 

Air-cells  of  lungs,  159, 160. 

Albumen,  29  ;  transformation  of,  into  fibrin, 
100 ;  quantity  of,  121. 

Albuminose,  61,  64. 

Alcohol,  use  of,  in  supporting  heat,  20 ;  effect 
of,  182,  406. 

Alexander,  expedition  of,  620. 

Alexandria,  library  of,  624. 

Aliment,  necessity  for,  10. 

Allan tois,  531. 

Allotropism  of  bodies,  188 ;  decay  depends 
on,  244. 

Alpha  and  Beta  lactic  acid,  75. 

Alphabetic  writing,  358. 

Alternate  consciousness,  330. 

Alternation  of  generations,  514,  537. 

Amber,  trade  in,  619. 

Amelioration  of  negro,  578. 

America,  discovery  of,  632  ;  spread  of  Chris- 
tianity in,  598 ;  Indians,  575. 

Amnion,  530. 

Amphibia,  blood  of,  121. 

Analogy  of  spinal  and  ventral  cord,  308. 

Analytical  mind  of  European,  592 ;  advan- 
tages of,  618,  635,  637. 

Animal,  capillary  circulation  of,  133 ;  heat 
illustrated  by  locomotive,  187 ;  makes  fat, 
247;  motion,  431. 

Animal  kingdom,  subdivisions  of,  176. 


Anterior  roots  of  spinal  cord,  296. 

Anthropomorphism,  286. 

Antrum  duodeni,  61 ;  pylori,  61. 

Ants,  habits  of,  605. 

Aplysia,  280. 

Apparitions,  402. 

Appendix  vermiformis,  63. 

Approach  of  sleep,  532. 

Aqueous  humor,  386. 

Arabs,  discoveries  of,  629 ;  influence  of,  629. 

Araucanians,  598. 

Arc,  automatic,  277  ;  cellated,  278  ;  influen- 
tial, 282;  commissured,279;  multiple,  278; 
registering,  281. 

Aristotle,  620. 

Arm,  580. 

Art,  contributions  of  Asia  to,  595. 

Arteries,  coats  of,  140  ;  contractility  of,  141 ; 
structure  of,  140. 

Article  of  death,  411. 

Artificial  larynx,  355. 

Ascaris  acuminata,  524 ;  nigrovenosa,  524. 

Ascent  of  sap,  causes  of,  87. 

Ascherson  on  use  of  fat,  101. 

Asia,  stationary  condition  of,  636. 

Asiatic  contributions,  595. 

Asterias,  nervous  system  of,  279. 

Astrology,  178. 

Atmosphere,  action  of,  on  plants,  464,  482. 

Attraction,  capillary,  104. 

AUDITORY  MECHANISM,  general  view  of, 
376. 

Auditory  muscles,  estimate  of  contraction  of, 
367;  nerve,"  361. 

Auricles  of  heart,  138,  146. 

Australian,  563 ;  forests,  474. 

Automata,  insects  are,  609. 

Automatic  arc,  277,  283 ;  registering,  281. 

Awakening,  553. 

Axmann  on  nerves,  263. 

B. 

BACON,  ROGER,  625. 

Balance  between  heating  and  cooling,  186. 
Barbarism,  604. 
Barral  on  food  distribution,  39. 
Basilar  view  of  skull,  584. 
Beaumont  on  food,  66. 
Becquerel,  table  from,  33. 
Bee,  formation  of  fat  by,  248. 
Beef,  digestibility  of,  65. 
Bell,  discoveries  of,  259,  298,  318. 
Beneke  on  hospital  diet,  35. 
Bernard  on  digestion,  76  ;  on  fat,  71 ;  on  sali- 
va, 196  ;  on  liver-sugar,  208. 
i  Bernouilli,  principle  of,  90. 


640 


INDEX. 


Berzelius  on  lactic  acid,  75;  on  perspiration, 
240. 

Bibra,  Von,  on  brain  fat,  274. 

Bidder  on  albuminates,  39 ;  on  section  of 
pneumogastric,  54. 

Bidder  and  Schmidt  on  intestinal  juice,  69  ; 
on  bile,  70 ;  table  by,  70. 

BILE,  secretion  of,  70,  110,  202  ;  composition 
of,  204;  formed  from  venous  blood,  110, 
303 ;  sources  of,  202  ;  aids  in  introducing 
fat,  91;  spiral  course  of,  201;  change  by 
retention  of,  205  ;'  period  of  maximum  flow 
of,  205  ;  not  formed  in  the  liver,  206 ;  man- 
ner of  removal  of,  206. 

Bipolar  nerve-cell,  264,  268. 

Bird,  digestive  tract  of,  58;  respiration  and 
heat  of,  159 ;  talking,  352. 

Bishop  of  Chiapa,  his  accusation,  632. 

Black  pigment,  387. 

Black  Sea  trade,  619. 

Blastodermic  vesicle,  524. 

Bligh  on  Pelagians,  580. 

BLOOD,  111;  properties  of,  112  ;  composition 
of,  112  ;  total  amount  in  body,  113  ;  coag- 
ulation of,  113 ;  buffy  coat  of,  114 ;  changes 
produced  in  by  respiration,  120,  126,  134 ; 
excretion  of  carbonic  acid  from,  126,  167 ; 
changes  of  color  of,  169  ;  density  of,  169 ; 
salts  of,  124 ;  gases  of,  125 ;  functions  of 
constituents,  125  ;  course  of,  134 ;  distribu- 
tion of,  144 ;  glandular  change  of,  190. 

Blood  of  spleen,  212. 

Blood-cells,  form  of,  1 15  ;  constitution  of, 
118;  origin  of,  94,  115;  destruction  of, 
209 ;  increase  of,  125 ;  diminution  of,  126 ; 
short  life  of,  127;  changes  in  form,  117; 
cell  wall  of,  is  fibrin,  117. 

Blood,  colorless,  corpuscles  of,  115,  120. 

Blood  crystals,  119. 

Bloodletting,  reduction  of  temperature  by, 
184. 

Blood-vessels,  origin  of,  528. 

Blumenbach's  method  of  examining  the  skull, 
582. 

Bone,  253;  sources  of,  257;  composition,  254 ; 
growth  of,  256. 

Bonito,  177. 

Boussingault  on  expiration,  39  ;  on  gum,  72  ; 
on  fat,  39,  229. 

Bovista  giganteum,  88. 

Bowman  on  kidney,  223. 

Brahmin,  573. 

Brain,  313.     See  Cerebrum  and  Cerebellum. 

Brazen  men,  634. 

Bread,  33  ;  use  of  butter  on,  34  ;  making  of, 
illustrates  digestion,  78  ;  sets  free  alcohol, 
79. 

Breath,  the  first,  148. 

Breathing,  act  of,  156. 

Bright  on  pancreas,  71. 

Bronchial  tubes,  159. 

Brown-Sequard  on  muscle,  443 ;  on  rigor 
mortis,  453  ;  on  spinal  cord,  299. 

Bruchium,  gardens  of,  621. 

Bud,  its  nature,  469. 

Budding,  469, 535 ;  reproduction  by,  495,  535. 
Buffon  on  infancy,  539. 


Buffy  coat,  114. 
Burning  lenses,  461. 
Butter,  making  of,  31. 


CALIFORNIANS,  576. 

Calorific  hypothesis  of  vision,  599. 

Calorifacient  digestion,  63. 

Camelopard,  491. 

Camera  obscura,  381. 

Camper's  method  of  examining  skulls,  581. 

Canaliculi,  253. 

Canals,  semicircular,  375. 

Cape  of  Good  Hope,  discovery  of,  34,  631. 

Cape  Hyrax,  stomach  of,  59. 

CAPILLARY  VESSELS,  39,  141,  160;  move- 
ment of  blood  in,  145  ;  of  muscle,  459. 

Capillary  absorption,  103  ;  attraction,  104  ; 
propositions  respecting,  105  ;  motion,  131. 

Capillary  circulation,  142 ;  phenomena  of, 
145  ;  in  acardiac  foetus,  144 ;  in  asphyxia, 
145;  local  excitement,  144. 

Carbohydrates,  71 ;  turn  into  fat,  81 ;  make 
up  deficit  of  albumen,  39. 

Carbonic  acid  excretion,  164;  sources  of,  164, 
252;  introduces  oxygen,  165  ;  decomposed 
by  light,  461.  v 

Carcinus  msenas,  510. 

Career  of  man,  612  ;  of  organic  form,  456. 

Carnivora  consume  themselves,  36  ;  fibrin  of 
their  blood,  123  ;  find  fat  in  their  food,  248. 

Carp,  lung  of,  157. 

Carpenter  on  nervous  system,  259 ;  on  sen- 
sorium,  319 ;  on  analogy  between  spinal 
and  ventral  cords,  307 ;  on  generation, 
537. 

CASEIN,  30,  31,  231 ;  pre-exists  in  plants,  36  ; 
changes  into  fibrin,  35  ;  dissolves  phos- 
phate of  lime,  35. 

Castle  building,  330. 

Catamenia,  519. 

Caudate  vesicles,  264. 

Causes  of  sleep,  552. 

CELLS,  primordial,  458  ;  simple  and  nucle- 
ated, 492;  animal,  496 ;  circulation  in,  132. 

Cells  of  blood,  116;  uses  of,  129;  numbers 
of,  in  different  animals,  121. 

Cells  of  kidney  remove  unoxidized  bodies, 

»  223. 

Cells  in  lungs,  159. 

Cells,  nerve,  264. 

Cellulose,  71. 

Centre  of  intellect,  635. 

Centres  of  nerves,  290. 

Centripetal  and  centrifugal  fibres,  265. 

Cephalic  ganglia,  271,  607. 

CEREBELLUM,  322;  development  of,  314  ±  ex- 
periments on,  323 ;  structure  and  function 
of,  322. 

Cerebral  sight,  401. 

Cerebro-spinal  fluid,  326. 

CEREBRUM,  structure  of,  317;   development 
of,  314;   aspects  of,  316  ;   tracts  of,  318; 
ganglia  at  base,  319;  weight  of,  325;  at- 
mospheric pressure  on,  326. 
Cheese,  making  of,  31. 


INDEX. 


641 


Cheselden's  case  of  cataract,  419 ;  on  the  ear, 
365. 

Chest,  type  of,  161. 

Chilians,  576. 

Chimpanzee,  581. 

Chinese,  574 ;  writing,  636. 

Chitin  in  wings  of  insects,  71. 

Chlorine  and  hydrogen,  471. 

Cholepyrrhin,  124. 

Cholera,  effect  of,  22. 

Cholesterine,  275. 

Chorda  dorsalis,  528. 

Chorion,  523 ;  changes  in,  525. 

Choroid  coat,  384 ;  function  of,  394. 

Chossat  on  inanition,  178,  243. 

CHBISTIAN  CHURCH,  626 ;  spread  of,  in  Amer- 
ica, 598. 

Chromatic  aberration,  386. 

Chronometer,  illustration  of  heart  by,  140. 

CHYLE,  53 ;  absorption  of,  87 ;  causes  of  the 
flow  of,  89 ;  composition  of,  92  ;  corpuscles, 
first  appearance  of,  94 ;  action  of  water  and 
acetic  acid  on,  94. 

Chyme,  53. 

Cilia,  431. 

Ciliated  animacule,  432. 

CIRCULATION,  145  ;  objects  of,  111,  134 ; 
changes  during,  126 ;  course  of,  134 ;  in 
plants,  132 ;  in  lower  animals,  135  ;  action 
of  heart  in,  138 ;  sounds  of  heart  in,  139 ; 
nervous  influence  on,  140 ;  foetal,  531 ;  pla- 
cental,  527;  portal,  134;  connection  of 
parts  by,  112 ;  dependence  of,  on  respira- 
tion, 133. 

Civil  law,  628. 

Civilization,  effect  of  climate  on,  599 ;  com- 
pared with  barbarism,  604. 

Classification  of  natural  history,  506  ;  of 
skulls,  586. 

Climates,  botanical,  481. 

Clock,  illustration  from,  485. 

Coagulation  of  blood,  113. 

Cochlea,  364,  368 ;  comparative  anatomy  of, 
373. 

Cceliac  axis,  ramifications  of,  49. 

Coinage,  introduction  of,  620. 

Cold-blooded  animals,  172, 176. 

Coleridge  on  dreams,  556. 

Colladon  on  diving-bell,  366. 

Color,  origin  of,  589. 

Colored  rays,  effect  of,  461. 

Colostrum,  225. 

Combustion,  artificial,  17 ;  organic,  17, 18. 

Commerce,  origin  of  European,  619. 

Comminution  instruments,  40. 

Commissures,  function  of  nervous,  280. 

Comparative  history,  612. 

Compartments  of  ruminant's  stomach,  60. 

Complemental  air,  165. 

Complexion  of  man,  571,  572. 

Conception,  530. 

Condensing  action  of  membranes,  155. 

Condition  of  dreams,  558. 

Condorcet  on  dreams,  556. 

Conductibility  in  nerves,  265. 

Conferva,  495. 

Congelation,  perpetual,  473. 

s 


Conjugation,  modification  of,  515. 
Consonants,  356 ;  explosive  and  continuous, 

357. 

Constant  temperature,  problem  of,  176. 
Constituents  of  plants,  sources  of,  4G3 ;  of  the 

blood,  functions  of,  125. 
Contarini,  Cardinal,  on  circumnavigation,  625. 
Contractile  fibre-cells,  435. 
CONTRACTILITY  of  muscle,  442,  449 ;  nature 

of,  442. 
Contraction,  hypothesis  of,  451 ;  by  water, 

451 ;  by  touch,  452  ;  after  death,  444. 
Control  of  heat  by  nerves,  186. 
Converging  media,  381. 
Cooling  agencies,  184. 
Cord,  spinal,  294 ;  conduction  by,  299. 
Cornea,  384. 
Corpuscles,  of  milk,  225 ;   of  fat,  246 ;   of 

blood,  116;  origin  of,  101, 115;  colorless, 

93, 115 ;  of  chyle,  93, 143 ;  proportion  of, 

125. 

Cotyledons,  526. 
Couch  on  metamorphosis,  510. 
Course  of  the  bile,  202. 
Crab,  edible,  510. 
Cranial  nerves,  333. 
Creatine,  447. 

Crevice,  passage  of  water  through,  105. 
Crime,  tendency  to,  543. 
Crises,  change  by,  148,  484. 
Crus  cerebri,  314 ;  cerebelli,  314. 
Crusades,  630. 
Crystalline  lens,  386. 
Crystals  of  blood,  119. 
Cutaneous  absorption,  98. 
Cuvier  on  organisms,  466. 
Cycles  of  progress,  512. 

D. 

DALTON  on  corpus  luteum,  522 ;  on  diffusion, 
152. 

Daubenton  on  skull,  580. 

Davy  on  animal  heat,  178;  on  meconium, 
203 ;  on  protoxide  of  nitrogen,  412. 

Deafness  in  diving-bell,  366 ;  partial,  of  infe- 
rior animals,  377. 

Death,  560 ;  from  accident  and  old  age,  561. 

Decay,  243. 

Deception,  404 ;  of  touch,  421. 

Deleau  on  the  voice,  356. 

Descartes  on  insects,  609. 

Descent  of  dhp,  causes  of,  87, 132. 

Despretz  on  animal  heat,  182. 

Deutencephalon,  292. 

DEVELOPMENT,  505 ;  of  the  ear,  378;  of  the 
eye,  380  ;  of  muscle,  440  ;  geometrical 
modes,  447 ;  of  bird,  35 ;  of  heart,  135. 

Diaphragm  movements,  161. 

Diastose  salivaire,  45. 

Diet,  34. 

Differences  in  men,  563. 

DIFFERENTIATION,  500 ;  causes  of,  502 ;  in- 
fluence of  heat  on,  503  ;  epochs  of,  504 ; 
defined,  511. 

DIFFUSION  of  gases,  152 ;  force  of,  153, 156; 
general  facts  of,  156 ;  effect  of,  162. 

S 


642 


INDEX. 


Diffusion  of  influence  in  granular  nerve  ma- 
terial, 268. 

DIGESTION,  nature  of,  16, 40, 52, 63 ;  object  of, 
61,66;  histogenetic,  63 ;  calorifacient,  63 ; 
is  mechanical  and  chemical,  57 ;  double, 
46  ;  processes  of,  as  insalivation,  40,  46 ; 
deglutition,  46 ;  passage  into  duodenum, 
52,  67 ;  passage  along  intestine,  67. 

Digestion,  artificial,  52,  54. 

Digestion  of  gum,  71 ;  of  cellulose,  71 ;  of 
starch,  72 ;  of  sugar,  72 ;  of  fat,  76 ;  intes- 
tinal and  stomach,  contrasted,  81. 

Digestive  tract,  divisions  of,  48 ;  of  insect, 
58 ;  of  various  animals,  59 ;  juices,  their  or- 
ganic ingredient,  77 ;  power  injured  by  sal- 
iva, 50. 

Discs  of  muscular  fasciculi,  436  ;  of  blood, 
see  Cells. 

Discus  proligerus,  520. 

Distribution,  vertical,  of  plants,  473 ;  of  heat, 
473. 

Diurnal  amount  of  air  used,  166. 

Diurnal  variations  of  heat,  178. 

Donne  on  saliva,  44. 

D'Orbigny  on  Inca  Indians,  487. 

Dormouse,  stomach  of,  59. 

Dorsal  cord,  293 ;  lamina,  527. 

Double  trains  of  thought,  329. 

Doubleness  of  brain,  327. 

Dowler's  experiments,  444. 

Draper,  J.  C.,  on  respiration,  168,  239  ;  on 
urea,  220. 

Dreaming,  555. 

Drowning,  restoration  from,  133. 

Drum  of  ear,  364. 

Duality  of  mind,  329. 

Duct,  thoracic,  90.    . 

Ductless  glands,  211. 

Ducts,  dotted,  498. 

Dufay,  law  of,  104. 

Dugong,  heart  of,  136. 

Dulong  on  animal  heat,  182. 

Dumas  on  fat,  248. 

Dutrochet  on  endosmosis,  106. 

Dyslysin,  83. 

Dytiscus,  438. 

E. 

EAR,  structure  of,  376 ;  external,  360  ;  action 

of,  359 ;  auditory  nerve  of,  368  ;  labyrinth 

of,  375  ;  tympanum  of,  365. 
Education,  effect  of,  330,  543.      . 
Edwards,  Milne,  on  crustaceans,  488 :  on  fat, 

248. 

Egg,  development  of  bird  from,  35. 
Egypt,  613,  614. 
Elasticity,  heat  of,  185. 
Elective  filtration,  196. 
Electrical  tastes,  430 ;  currents  in  muscles, 

443 ;  conductors,  nerves  resemble,  266. 
Electricity,  275. 
Eleventh  pair,  342. 
Elixir  of  life,  633. 
Elliptical  skull,  586. 
EMBRYO,  538  ;  germinal  membrane  of,  525  ; 

vertebral  column  of,  532 ;  vascular  area  of, 


527 ;  allantois,  538 ;  circulation,  531 ;  in- 
fluence of  mother,  534 ;  size  and  weight  of, 
at  birth,  540,  541  j  viability  of,  545. 

Embryonic  development  of  brain,  313 ;  of 
circulating  apparatus,  531 ;  forms,  507. 

Emergence  of  impressions  from  brain,  408. 

Emotions,  mental,  290. 

Empiricism,  extinction  of,  25. 

Endocardium,  137. 

Endochrome,  493. 

Endogenous  generation,  496. 

Endosmosis,  105,  107,  131 ;  through  films, 
154 ;  through  stucco,  107 ;  force  of,  107, 
153. 

Enteric  juice,  369. 

Epencephalon,  292,  528. 

Epidermis,  233 ;  functions,  234. 

Epithelium,  197,  234  ;  cylindric,  tesselated, 
ciliated,  197. 

Epochs  of  globe,  481 ;  of  life,  547. 

Equilibrium,  conditions  of,  10,  22,  560. 

Erect  vision,  396. 

Esquimaux,  568. 

Europe,  primitive  state  of,  613. 

European  history,  610. 

Eustachian  tube,  367. 

Euthanasia,  561. 

Evaporation,  185. 

Excretion,  213. 

Exhalation  by  lungs,  21,  22. 

Exosmosis,  106,  131. 

Expectoration,  47. 

Explosive  consonants,  357. 

Extinction  of  Indians,  600. 

Extinctions,  484,  488. 

EYE,  structure  of,  382 ;  nervous  mechanism 
of,  389,  394 ;  accessary  apparatus  of,  399. 

Eyeball,  motions  of,  401. 

Eyebrows,  399. 

Eyelids,  399. 

F. 

FABRICIUS  AB  AQUAPENDENTE  on  veins,  130. 

Faeces,  83. 

Fair  races,  disappearance  of,  591,  636. 

Falling,  sensation  of,  559. 

Fasciculi  of  muscle,  433,  436 ;  digestion  of, 
54. 

FAT,  246 ;  oxidizes  gradually,  252  ;  relation 
of,  to  bile,  207 ;  to  nitrogenized  tissue,  250  ; 
in  articles  of  forage,  229 ;  emulsifying  of, 
71 ;  produced  from  carbohydrates,  81 ;  in- 
troduction into  villi,  91 ;  saponification  of, 
93. 

Faunal  groups,  568. 

Feeling  and  touching,  distinction  between, 
422. 

Female  and  male  compared,  546. 

Fenestra  ovalis  and  rotunda,  361. 

Ferments,  45,  80. 

Feudal  system,  631. 

FIBRIN,  30,  93,  97,  114;  loss  of,  52;  vegeta- 
ble, 33 ;  not  an  effete  body,  98  ;  organiza- 
tion, 113;  difference  of,  in  blood  and  mus~ 
cle,  114;  variations  in  quantity,  122. 

Fifth  pair  of  nerves,  334. 


INDEX. 


643 


Filtering  action  of  glands,  191. 

Filtration,  elective,  196. 

Final  agony,  562. 

Finite  nature  of  knowledge,  289. 

Fire-place,  exhausting  nature  of,  181. 

First  breath,  485. 

First  pair  of  nerves,  425. 

Fishes,  digestion  of,  60 ;  circulation  in,  135  ; 
respiration  of,  150, 157. 

Flame  and  plant,  analogy  between,  470. 

Floral  groups,  568. 

Flour,  33. 

Foetus,  circulation  in,  531.     See  Embryo. 

Follicles,  gastric,  49,  50 ;  varieties  of,  51. 

FOOD,  16,  26 ;  sources  of,  27 ;  classification 
of,  27 ;  value  of,  28 ;  different  kinds  of,  27, 
28;  of  carnivora,  36 ;  of  herbivora,  36, 37 ; 
nitrogen,  27,  35  ;  movements  of,  53  ;  ad- 
justs temperature,  179 ;  demand  for,  179 ; 
allowance  of,  11 ;  digestibility  of,  36,  66 ; 
formed  by  plants  and  destroyed  by  animals, 
37 ;  minimum  quantity  of,  38. 

Foramen  magnum,  580. 

Force  of  endosmosis,  107. 

Forge tfulness  of  dreams,  557. 

Formic  acid,  240. 

Fourcroy  on  perspiration,  240. 

Fourth  pair  of  nerves,  334. 

Fowl,  digestive  tract  of,  58. 

Franklin  on  heat,  380. 

Frerichs  on  food,  35 ;  on  saliva,  44. 

Frog,  lungs  of,  159  ;  development  of,  509. 

Front  view  of  skull,  585. 

Future  state,  551. 

G. 

GALILEO,  455. 

Gall  on  brain,  259. 

Gall-bladder,  199. 

Galvani,  experiments  of,  443. 

GANGLIA,  structure  of,  263 ;  spontaneous  func- 
tion, 289  ;  of  sympathetic,  140,  264  ;  of 
special  sense,  315  ;  cephalic,  607. 

Gases  of  intestine,  82. 

GASTRIC  changes  are  subdivisions  and  assim- 
ilation of  water,  62. 

Gastric  juice,  49,  50  ;  quantity  of,  52  ;  acid 
of,  52, 54 ;  relation  of  nervous  influence  to, 
54. 

Gelatine,  64,  65. 

Gemmation,  534. 

GENERATION,  515, 516 ;  spermatozoa  in,  517, 
518. 

Geographical  distribution,  567. 

Geography  of  plants,  472. 

Geological  changes,  480. 

Geometrical  modes  of  development,  457. 

Germ-cell,  519. 

Germinal  membrane,  525  ;  its  layers,  527  ; 
vesicle  and  spot,  521. 

Germination,  458;  heat  of,  176. 

Gestation,  533. 

Gibraltar,  Straits  of,  620. 

Gills,  135,  150,  157. 

GLAND,  189  ;  type  of,  189,  197 ;  vicarious  ac- 
tion of,  190 ;  filtering  action  of,  190 ;  par- 


otid, 43  ;   salivary,  43  ;   submaxillary,  43 ; 

sublingual,  43  ;  mesenteric,  89  ;  ductless, 

211 ;  mammary,  225. 
Glandular  blood,  change  in,  190. 
Globulin,  118. 

Glosso-pharyngeal  nerve,  338. 
Glucose,  73. 
Gluten,  33. 
Glycerine,  245. 
Goodsir  on  lymphatics,  97. 
Graafian  follicle,  521. 
Gradual  death,  561. 
Grafting,  469,  535. 
Graham  on  diffusion,  152, 154. 
Greeks,  613 ;  schools  of,  617. 
Growth,  511,  538,  540 ;  conditions  of,  465. 
Guinea,  negro  of,  579. 
Gum,  digestion  of,  71. 
Gundelach  on  fat,  248. 

H. 

HABITS  OF  NATIONS,  566,  569 ;  of  insects, 
605. 

Hsematin,  118 ;  analysis  of,  119. 

Hsematococcus  binalis,  494. 

Hair,  236. 

Hall,  discoveries  of,  259. 

Hallucination,  402. 

Harvey  on  circulation,  130. 

HEARING,  sense  of,  359 ;  structure  of  organ 
of,  360 ;  use  of  tympanum  in,  364 ;  audi- 
tory nerve  of,  368. 

HEART,  135 ;  fibres  of,  137 ;  valves  of,  138 ; 
development  of,  135 ;  of  dugong,  136 ;  ac- 
tion of  nerves  on,  140 ;  statement  of  action 
of,  147 ;  number  of  beats  of,  130. 

HEAT,  17, 18, 19, 20;  check  upon,  21, 22, 184 ; 
equilibrium  of,  22 ;  animal,  175,  177;  car- 
bonic acid,  relation  to,  19,  20,  176  ;  varia- 
tions, 178;  diurnal,  178 ;  extreme,  endura- 
ble, 178;  annual,  179;  source  of,  182;  of 
light  rays,  389 ;  removed  from  muscle,  447 ; 
quantity  for  plants,  477  ;  intensity  and 
quantity  of,  477 ;  decline  of,  488 ;  relations 
of,  572  ;  effect  of,  on  skull,  590. 

Heaths,  absence  of,  from  America,  474. 

Height  of  man,  541. 

Helmholtz  on  nerve,  266 ;  on  muscle,  445. 

Hepatic  artery,  200 ;  cells,  duct,  vein,  200, 
206. 

Herbivora,  36. 

Herculaneum,  465. 

Hereditary  transmission,  590. 

Hermaphroditism,  574. 

Hibbert  on  apparitions,  408. 

Hippocratic  face,  561. 

Histogenetic  digestion,  40,  63. 

HISTORY  a  branch  of  Physiology,  604 ;  Euro- 
pean, 610 ;  universal,  611 ;  prognostics  in, 
612 ;  comparative,  612. 

Homogenesis  and  heterogenesis,  511. 

Hot-blooded  animals,  176. 

Hottentots,  577. 

Hubbenet,  table  by,  49. 

Huber,  556. 

Human  groups,  568. 


644 


INDEX. 


Humboldt  on  respiration,  158  ;  on  plants,  471. 

Humors  of  the  eye,  386. 

Hunter  on  reflexa,  596. 

Hutchison  on  respiration,  166. 

Hybernating  animals,  172,  183. 

Hydra,  5 1,52,  432,  501,  534. 

Hydraulic  action  of  auricle,  146. 

Hydrochloric  acid,  52,  62. 

Hydrogen,  use  of,  17,  19. 

Hypoglossal  nerve,  343. 


I. 


IDEAL  type  of  man,  565. 

Idiot,  composition  of  brain  of,  273. 

Illusions,  402. 

Imago,  5.11. 

Immortality  of  the  soul,  415. 

Impersonal  operations,.  287. 

Impressions,  vestiges  of,  288. 

Improvability  of  man,  15. 

Inanition,  experiments  on,  178,  243. 

Inca  Indians,  487. 

Incombustible  men,  634. 

Independence  and  immortality  of  the  soul, 
285. 

Independent  action  of  each  half  of  the  brain, 
328. 

Index  of  prohibited  books,  624. 

Indians,  575 ;  extinction  of,  600. 

India-rubber,  diffusion  through,  152. 

Individuality,  nature  of,  468. 

Indo-Europeans,  573. 

Infancy  of  man,  538.   . 

Inflorescence,  heat  of,  176. 

Influence  of  agents  on  man,  563,  567,  571 ; 
of  parent  on  child,  534. 

Influential  arc,  282. 

Infusorials,  heat  of,  177. 

Inosite,  447. 

Inquisition,  establishment  of,  624. 

Insalivation,  40. 

Insanity  of  retina,  406. 

INSECT,  digestive  tract  of,  58 ;  cephalic  gan- 
glia, 271 ;  nervous  system,  271 ;  respira- 
tion of,  157;  development  of,  510;  struc- 
ture and  habit  of,  603,  605 ;  memory  and 
metamorphoses  of,  608. 

Instantaneousness  of  dreams,  556. 

Instinct  distinguished  from  reason,  603. 

Insubordination  of  one  hemisphere,  329. 

Intellect,  maximum  of,  591 ;  centre  of,  635. 

Intensity,  adjustment  for  variations  of,  in 
eye,  388. 

Intensity  of  heat,  477,  572. 

Interference,  mechanism  of,  in  ear,  372 ;  of 
nervous  impressions,  269. 

Interstitial  death,  244 ;  movements,  151. 

INTESTINE,  length  of,  42  ;  salts  and  gases  of, 
82  ;  digestion  in,  63,  68,  81  ;  contents, 
changes  of,  83  ;  section  of  wall  of,  85 ;  per- 
istaltic movements  of,  68  ;  passage  of  food 
through,  67,  81 :  glands  and  secretion  of, 
69,  70; 

Inverse  problems,  284, 482. 

INVERSE  VISION,  401 ;  use  of,  416. 

Iris,  385. 


Iron  acted  on  by  gastric  juice,  50 ;  source  of, 

in  blood-cells,  118. 
Irrespirable  gas,  action  of,  133,  169. 
Isaacs  on  kidney,  217. 

J. 

JACKSON  on  the  ear,  373. 

Jacob's  membrane,  390. 

Jeffreys  on  respiration,  165. 

Jesuits,  624. 

Jones,  Bence,  on  urine,  221. 

Jones,  Handfield,  on  hepatic  cells,  206. 

Jones,  W.,  on  blood-cells,  117. 

K. 

KAFFIRS,  577. 

Kamtschatdale,  575. 

Kangaroo,  59. 

Kidney,  213 ;  structure  of,  214 ;  tubuli  uri- 
niferi  of,  215 ;  circulation  in,  215 ;  devel- 
opment of,  214 ;  vicarious  action,  186. 

Kiestine,  231. 

Kolliker  on  skin,  420 ;  on  retina,  391 ;  spleen, 
211. 

Koumiss,  80. 

Krause  on  sebaceous  secretion,  240. 

Kreatine,  447. 

Kune  on  bile,  203. 


L. 


LABYRINTH,  361. 

Lachrymal  gland,  400. 

Lacteals,  84,  86,  87, 91,  111 ;  function  of,  85 ; 
and  lymphatics,  connection  of,  with  respi- 
ration, 100. 

Lactic  acid,  47,  52,  73,  74,  75. 

Lacunas  of  bone,  253. 

Lamina  spiralis,  359. 

Landerer  on  perspiration,  240. 

Languages,  357. 

Laplander,  568. 

Larva,  510. 

Larynx,  353  ;  double,  of  birds,  352 ;  artificial, 
355. 

Lateral  inversion,  397. 

Lateral  view  of  skull,  581. 

Law,  civil,  628. 

Lawrence  on  the  leg,  580. 

Laycock  on  cephalic  ganglia,  607. 

Leg,  580. 

Legumin,  33. 

Lehmann  on  absorbed  nitrogen,  39 ;  pep- 
tones, 62 ;  gastric  solution,  66 ;  gum,  72 ; 
urine,  75  ;  quantity  of  blood,  113 ;  blood 
crystals,  120;  bile,  203 ;  kiestine,  231. 

Leidy  on  liver,  198. 

Length  of  infant,  540 ;  of  sleep,  553. 

L'Heritier  on  chyle,  96. 

Lieberkuhn,  follicles  of,  69. 

Liebig  on  lactic  acid,  75;  on  fibrin,  98;  on 
blood  gases,  125. 

Life,  conditions  of,  9, 12. 

Light,  nature  of,  399 ;  influence  of,  459. 

Lime,  phosphate  of,  35. 


INDEX. 


645 


Liquor,  sanguinis,  121 ;  amnii,  530. 

LIVER,  209  ;  structure  of,  199,  200,  201 ;  de- 
velopment of,  191,  198  ;  secretion,  203, 
205 ;  sugar,  123 ;  production  of  sugar  and 
fat  in,  207 ;  destruction  of  blood-cells  in, 
209 ;  absorbed  material  goes  to,  107 ;  effect 
of,  on  complexion,  588.  See  Bile. 

Localization  of  functions  in  brain,  324^  of 
plants  and  animals,  482. 

Longevity,  545. 

Loss  of  perception  of  time,  332. 

LUNGS,  structure  of,  157, 159, 160;  capillaries 
of,  160;  capacity  of,  162 ;  organic  fibres  of, 
163 ;  chemical  changes  in,  163.  See  Res- 
piration. 

Luther,  Martin,  vision  of,  406. 

Luxury,  effect  of,  on  skull,. 588. 

Lymph,  95 ;  salts  of,  96 ;  flow  of,  99. 

Lymphatic  glands,  94. 

LYMPHATICS,  distribution  of,  97 ;  function  of, 
96,  98 ;  origin  of,  529. 

M. 

MACEDONIAN  CAMPAIGN,  620. 

Machines,  speaking,  356. 

Madagascar,  native  of,  577. 

Madder  in  bone,  256. 

Magellan,  voyage  of,  624. 

Male  and  female,  comparison  of,  546. 

Malpighian  bodies,  215 ;  sac,  removal  of  li- 
quid from,  224. 

Mammary  gland,  224 ;  development  of,  225  ; 
action,  233. 

Man,  physical  aspect  of,  24 ;  soul  of,  25 ;  ma- 
turity of,  542. 

Margarine,  246. 

Mariolatry,  631. 

Marmots,  172. 

Mastication,  40. 

Matters  received,  16  ;  dismissed,  17. 

Maturity  of  man,  542. 

Meconium,  202. 

Medulla  oblongata,  304 ;  functions  of,  306. 

Melloni  on  light,  389. 

Membrana  granulosa,  520 ;  decidua,  525, 526. 

Membranes,  selecting  power  of,  107. 

Memory  of  insects,  608. 

Menstruation,  519. 

Mental  emotions,  nature  of,  290. 

Mental  hallucination,  402. 

Mental  qualities  of  different  nations,  592. 

Mental  strength,  maximum  of,  544. 

Mesencephalon,  292,  528. 

Mesenteric  glands,  structure  of,  89 ;  plexuses, 
350. 

Metacetonic  acid,  246. 

Metamorphosis,  490. 

Metamorphosis  of  batrachians,  509. 

Metaphysics,  259. 

Midnight  sun,  476. 

MILK,  29,  31,  32 ;  casein  of,  29,  227,  231 ; 
sugar  of,  31,  227,  233 ;  butter  of,  31 ;  salts 
of,  31,  228 ;  lactic  acid  of,  31 ;  effect  of 
disease  of,  33  ;  composition  of,  225,  226  ; 
analysis  of,  226  •  vicarious  secretion  of,  228. 

Mind,  24. 


Miracles,  true,  624. 

Mitchell  on  diffusion,  152. 

Mohammedanism,  influence  of,  629 ;  spread 
of,  in  Africa,  597. 

Moisture,  influence  of,  475. 

Mongols,  574. 

Monogamy,  594. 

Monotheism,  601. 

Mortality,  545. 

Motion,  ciliary,  431 ;  muscular,  432. 

Motor  oculi  nerve,  391. 

Motor  tract  of  brain,  319;  of  cord,  303. 

Mouth,  functions  of,  40. 

Mozambique,  native  of,  578, 

Mucous  membrane,  196 ;  layer,  527. 

Mucus,  43,  197;  buccal,  43. 

Mulberry  mass,  523. 

Miiller  on  bile,  203;  on  vision,  391 ;  on  voice, 
354. 

Multipolar  nerve-cell,  264,  268. 

Municipal  system,  623. 

Muscse  volitantes,  404. 

Muscle  juice,  434,  437. 

MUSCULAR  FIBRE,  structure  of,  433 ;  non-stri- 
ated, 435,;  motion  of,  432  ;  movements,  co- 
ordination of,  323 ;  contraction  of,  436  ; 
reparation  of,  446 ;  blood-vessels  of,  440 ; 
contraction  of,  after  death,  444 ;  develop- 
ment of,  440 ;  analysis  of,  441 ;  capillaries 
of,  439 ;  effects  of  electricity  on,  443. 

Muza,  his  threat,  623. 

N. 

NAILS,  236. 

Narwhal,  177. 

Nations,  origin  of,  568 ;  habits  of,  569 ;  prog- 
ress of,  600. 

Natural  history,  classification  of,  506. 

Negro,  579. 

Neill  on  villi,  60. 

NERVES,  division  of,  259 ;  rate  of  conduction 
in,  265 ;  sheath  of,  261 ;  fibres  of,  262  ; 
function  of  fibres,  265 ;  function  of  vesicles, 
267 ;  necessity  of  rest  for,  272. 

Nervous  agency,  magazines  of,  268 ;  trans- 
mission of,  265 ;  retention  of,  269 ;  inter- 
ference of,  269. 

Nervous  arcs,  277 ;  condition  for  action,  283 ; 
centres,  290. 

Nervous  system,  258  ;  controls  heat,  186 ;  de- 
velopment of,  292 ;  metamorphosis  of,  608  ; 
structure  and  functions  of,  293. 

Nervous  vesicular  matter,  260 ;  ganglia,  263  ; 
activity,  267;  tissue,  composition  of,  273; 
regeneration,  274. 

Newport  on  insects,  309. 

Newton,  colored  rings  of,  105. 

Nicolai  on  apparitions,  406. 

Nightmare,  559. 

Night  sleep,  554. 

Ninth  pair  of  nerves,  338. 

Nitrogen,  use  of,  16 ;  in  respiration,  171 ;  prot- 
oxide of,  412. 

Nodal  lines,  371. 

Non-striated  fibre,  435. 

Nose,  424. 


646 


INDEX. 


Nucleated  cells,  circulation  in,  131. 

Nucleine,  117. 

Nucleus,  493. 

NUTRITION,  245,  252 ;  connection  with  nerv- 
ous agency,  186,  244 ;  selecting  power  in, 
245 ;  three  types  of,  532 ;  of  carnivora  and 
herbivora,  36. 

O. 

OBJECTIVE  OPERATIONS,  287. 

Ocelli,  380. 

Octopus,  nervous  system  of,  279. 

Ocular  spectra,  396. 

Oculo-motor  nerve,  333. 

ODORS,  sensibility  to,  424 ;  localization  of, 
426. 

Odyssey,  613. 

Oil,  emulsifying  of,  71 ;  globules  on  villus,  88. 

Old  age,  545. 

Oleaginous  principles  of  food,  36, 81. 

Oleine,  246. 

Olfactory  organ,  mechanism  of,  424. 

Olivary  bodies,  304,  314. 

Omphalo-mesenteric  duct,  530 ;  vessels,  531, 

Operations,  plants  are,  470. 

Opium,  effects  of,  406. 

Optic  nerve,  391. 

Orang,  581. 

ORGANIC  FORM,  career  of,  456. 

Organic  life,  nerve  of,  344. 

Organic  periodicities  connected  with  heat, 
179. 

Organisms,  metamorphosis  of,  489. 

Organization,  principle  of,  457. 

Organized  bodies,  allotropism  of,  188. 

Organs  of  sense,  359. 

Origin  of  nations,  568. 

Ornithorynchus,  224. 

Ossicles,  367. 

Ossification,  255. 

Osterlein  on  villi,  86. 

Ostrich,  stomach  of,  59. 

Oval  skull,  586. 

Ovarium,  origin  of  ova  in,  520 ;  corpus  lute- 
urn  of,  522. 

Ovisac,  520. 

OVUM,  521 ;  discharge  of  from  ovary,  523  ; 
changes  of,  524 ;  segmentation  of,  524. 

Owen  on  the  arm,  380  ;  on  skull,  532,  584. 

Oxalic  acid  in  urine,  222. 

OXYGEN,  uses  of,  47, 101, 134 ;  in  respiration, 
134,  163, 182 ;  influence  of,  on  blood,  126 ; 
changes  albumen  into  fibrin,  101, 176 ;  lib- 
erated by  plants,  461. 

P. 

PACINIAN  BODIES,  420. 

Paganism,  fall  of,  622. 

Paine,  Professor,  on  plants,  478. 

Pale  people,  disappearance  of,  in  Europe,  634. 

Palingenesis,  634. 

Pancreas,  68 ;  juice  of,  68. 

Pantheism,  288. 

Papal  government,  623. 

Papillae  of  skin,  419  ;  of  tongue,  428. 


Parotid  gland,  43. 

Parturition,  533. 

Par  vagum,  340 ;  influence  of,  on  liver,  208. 

Patagonians,  578. 

Patella,  nervous  system  of,  279. 

Pathetici,  334. 

Patina,  151. 

Pelagian  type,  579. 

Pepsin,  49,  54,  55. 

Peptones,  50,  53,  62. 

Perception  of  time,  loss  of,  332. 

Pericardium,  137. 

Peristaltic  movements,  53. 

Peroxalate  of  iron  decomposed  by  light,  461. 

Persecution,  result  of,  624. 

Persian  empire,  616. 

Perspiration,  238. 

Persuasions,  544. 

Peruvian,  576. 

Peyer's  bodies,  70,  94. 

Phantasms,  localization  of,  415. 

Philippine  negro,  578. 

Philosopher's  stone,  633. 

Philosophy,  suppression  of,  624. 

Phrenicians,  619. 

Phosphorus,  17,  23,  27,  32,  275. 

Photographic  effects  of  temperature,  393. 

Phrenic  nerve,  344. 

Phrenology,  324. 

PHYSIOLOGY,  subdivisions  of,  26 ;  statical,  9  ; 
dynamical,  455. 

Piles  of  Bitter,  277. 

Pine,  woody  fibre  of,  498. 

Placenta,  526. 

PLANTS,  individuality  of,  468  ;  quantity  of 
heat  for,  467 ;  secular  changes  of,  480 ;  lo- 
calization, 482. 

Plasma,  121. 

Plastic  power,  459,  471. 

Pneumogastric  nerve,  340. 

Polygamy,  594. 

Polype,  51. 

Polytheism,  601. 
i  Pompeii,  465. 
:  Pons  varolii,  307. 
i  Porcupine,  59. 

Porpoise,  stomach  of,  59. 
'  Portal  circulation,  119, 134,  201,  202. 

Ports  of  Egypt,  opening  of,  616. 

Posterior  roots  of  spinal  nerves,  296. 

Potassium,  iodide  of,  experiments  with,  47, 
52. 

Powder  of  projection,  633. 

Pre-existence,  sentiment  of,  331. 

Prevost  and  Dumas  on  muscle,  439. 

Prichard  on  habits  of  men,  569 ;  on  skull, 
580,  585. 

Priestley  on  gaseous  endosmosis,  151. 

Primitive  trace,  293,  527. 

Primordial  cell,  458. 

Principle  of  organization,  457. 

Printing,  358. 

Prognathous  skull,  586. 

Protein  bodies  removed  by  urine,  220,  222. 

Provencal  on  respiration,  155. 

Psammetichus,  615. 

Psychical  powers,  327. 


INDEX. 


647 


Ptolemies,  621. 

Ptyaline,  45. 

Pulsation  of  heart,  138 ;  of  arteries,  141. 

Pulse,  139. 

Pupa,  511. 

Pyramidal  skull,  586. 

Pyramids,  anterior  and  posterior,  304. 

Q- 

QUAIN  ON  ADIPOCIRE,  247. 

Quality  of  sounds,  estimation  of,  375. 
Quantity  of  heat,  477. 
Quetelet,  researches  of,  15,  540. 
Quick  respiration,  effect  of,  168. 
Quincey,  De,  on  opium,  407. 

R. 

EADIAL  fibre  system,  390. 

Radiation  of  heat,  185. 

Ramlike  action  of  heart,  147. 

Rarefied  air,  effect  of,  183. 

Ray  on  insect  habits,  606. 

Reaumur  on  digestion,  55. 

Reduction  of  temperature,  184. 

Reflex  action,  280 ;  of  insects,  609. 

Reformation,  619,  625. 

Registered  impressions,  414. 

Registering  ganglia,  259 ;  nerve  arc,  281 , 282. 

Registry  of  sounds,  358. 

Regnault  and  Reiset  on  respiration,  170. 

Repair,  necessity  of,  244. 

Reparation,  23. 

REPRODUCTION  of  cells,  494 ;  and  develop- 
ment, 505 ;  closes  development,  513. 

Reptile  respiration,  158. 

Residual  air,  165. 

RESPIRATION,  151,  156,  157,  170,  171,  174; 
water  removed  by,  168 ;  gases  of,  163, 167, 
171,176;  movements  in,  162;  movements 
of  air  in,  163 ;  number  of  movements,  162  ; 
influence  of  nervous  agents  on,  173;  gen- 
eral statement  of,  174. 

Respiratory  digestion,  63. 

Restiform  bodies,  304. 

Resurrection  of  roses,  634. 

RETINA,  390, 392, 394 ;  structure  of,  385, 390 ; 
disturbance  of,  405. 

Retzius  on  stomach,  61. 

Reynoso  on  sugar,  208. 

Rhakotis,  621. 

Rhythmic  contractions,  448. 

Rigor  mortis,  452. 

Roman  coins,  151. 

Roman  empire,  622. 

Rotation  of  animals,  324. 

Rudimentary  organs,  491. 

Rudimentary  sounds,  325. 

Rumford  on  clothing,  180. 

Ruminant,  stomach  of,  59. 

Running,  454. 

S. 

SABBATH  DAY,  627. 
Sahara,  Desert  of,  475. 


Saladin,  631. 

SALIVA,  43;  action  of,  46;  quantity  of,  44, 

47 ;  specific  gravity  of,  44 ;  composition  of 

45 ;  action  of,  in  stomach,  46, 50 ;  aeration 

by,  47. 

Salivary  glands,  43. 
Salpse,  537. 
Salt,  use  of,  62. 
Samoiedes,  568. 
Sankey  on  brain,  325. 
Sap,  ascending,  87,  132. 
Sarcolemma,  433,  438. 
Scalse  of  ear,  368. 
Scherer  on  urine,  221. 
Schlossberger  on  brain,  274. 
Schmidt  on  albuminates,  39 ;  on  blood-cells, 

119 ;  on  pneumogastric,  54 ;  on  pepsin,  55 ; 

on  pancreatic  juice,  68 ;  on  intestinal  wa- 
ter, 83 ;  on  transudation,  95. 
Schneiderian  membrane,  424. 
Schultz  on  muscle  juice,  434. 
Schwann  on  nerves,  261. 
Science,  contributions  of  Asia  to,  596. 
Sclerotic,  384. 

Scot,  Reginald,  on  spirits,  407. 
Scott,  Walter,  on  lying,  404. 
Sebaceous  glands,  227.  „ 

Secreted  matters  pre-exist  in  blood,  192, 195. 
Secretion,  189 ;  structures  for,  193 ;  by  serous 

membranes,  193 ;  by  mucous,  196. 
Seeing.    See  Vision. 
Seguin  on  exhalation,  238. 
Selecting  power,  99. 
Semicircular  canals,  361,  364,  374. 
Sensation  of  falling,  559. 
Senses,  359. 
Sensorium,  281,319. 
Sensory  tract  of  cord,  303, 320 ;  of  brain,  320 ; 

ganglia,  282. 

Sentiment  of  pre-existence,  331. 
SEROUS  fluids,  193. 
Serous  layer,  527. 
Serous  membrane,  193. 
Serpents,  legs  of,  491. 
Serum,  salts  of,  96. 
Seventh  pair,  337. 
Sexes,  mortality  of,  545. 
Shelter,  imperfections  of,  181. 
Sight,  cerebral,  401. 
Silk-worm,  489. 
Silver  balls  in  digestion,  55. 
Singing,  355. 
Single  vision,  395. 
Sisocles,  582. 
Sixth  pair,  334. 
Skeleton,  253,  580. 
SKIN,  233 ;  absorption  by,  241 ;  transpiration 

from,  185,  237 ;  glands  of,  235 ;  exudation 

of,  185,  239. 
SKULLS,  examination  of,  581  ;  forms  of,  582; 

classification  of,  586 ;   effect  of  heat  on, 

590. 

Slack  on  circulation  in  cells,  132. 
Sleep,  551. 

Slow  respiration,  168. 
Smell,  423 ;  condition  of,  425. 
Soap-bubble,  dilf  i-ion  through,  153. 


648 


INDEX. 


Social  mechanics,  602. 

Society  of  insects,  604. 

Sociology,  comparative,  602. 

Sodium,  chloride  of,  62 ;  use  of,  77. 

Soemmering  on  leg,  580 ;  spot  of,  385,  397. 

Soil,  influence  of,  476. 

Solar  plexus,  350. 

Somnambulism,  557. 

Song  and  speech,  distinctions  of,  352. 

SOUL,  existence  of,  283  ;  independence  of, 
285,  548. 

SOUND,  peculiarities  of,  361 ;  analogy  of,  to 
light,  379 ;  articulate,  539. 

Spain,  colonial  empire  of,  632. 

Spallanzani  on  food,  65. 

Speaking  machines,  356. 

Species  of  plants,  479 ;  changes  in,  480,  484. 

Speech,  539. 

Spermatic  fluid,  517. 

Spermatozoa,  517 ;  development  of,  518. 

Sperm-cell,  516. 

Spherical  aberration,  386. 

Sphinx  ligustri,  279,  308,  313,  607. 

Spinal  axis,  291. 

SPINAL  CORD,  294, 296 ;  reflex  action  of,  300 ; 
comparative  anatomy  of,  300 ;  divisions  of, 
296 ;  connection  of,  with  brain,  302 ;  func- 
tions of,  303. 

Spinal  nerves,  roots  of,  303. 

Spiracle  of  insect,  157,  352. 

Spiral  vessels,  498. 

Spirit,  24. 

Spirostreptus,  301. 

Spissitude  of  blood,  169, 190. 

Spitting,  habit  of,  47. 

Spleen,  211. 

Spongioles,  87,  466. 

Spontaneous  gemmation,  536. 

Stages  in  introduction  of  air,  160. 

Standards,  fixed  physiological,  13 ;  tables  of, 
15. 

Standing,  453. 

Stapedius,  365. 

Starch,  71. 

Starvation,  182. 

Stearine,  246. 

Steenstrup  on  generation,  537. 

Steno,  duct  of,  43. 

Stereoscope,  397. 

Still  layer,  143. 

STOMACH,  41,  42;  types  of,  42  ;  temperature 
of,  49 ;  regions  of,  60 ;  histogenetic  diges- 
tion of,  63 ;  blood-vessels  of,  102 ;  mucous 
surface  of,  50, 58 ;  follicles  of,  50 ;  hydroid 
nature  of,  51 ;  trituration  by,  55 ;  secre- 
tions of,  48 ;  various  forms  of,  59  ;  move- 
ments of,  52. 

Stove,  warming  by,  181. 

Strecker  on  bile,  204. 

Striated  muscular  fibre,  433,  436. 

Stucco,  endosmosis  through,  107,  152. 

Subdivisions  influenced  by  heat,  79. 

Subjective  operations,  287 ;  images,  398. 

Submaxillary  saliva,  43. 

Suction,  act  of,  228. 

Sudoriparous  glands,  237,  238. 

Sulphocyanide  of  potassium,  43. 


Sulphur,  17,  23,  27. 

Sunlight,  458 ;  consumption  of,  459 ;  uses  of, 

466  ;'  variation  of,  483. 
Supplemental  air,  165. 
Supra-renal  capsules,  214. 
Swimming  bladder,  157. 
SYMPATHETIC  SYSTEM,  344;  peculiar  fibres 

of,  262 ;   origin  of,  345  ;   connected  with 

spinal,  345  ;  ganglia  of,  346. 
Sympathy  depends  on  circulation,  112. 
Synthetical  mind  of  Asiatic,  592. 
Syntonin,  438. 
Systemic  circulation,  134. 

T. 

TADPOLE,  experiments  with,  489. 

Talking  birds,  352. 

Taste,  427 ;  nerves  of,  429. 

Taurine,  204,  208. 

Teeth,  40 ;  development  of,  539. 

Teleology,  415. 

TEMPERATURE,  effect  of,  on  body,  177  on 
skull,  590 ;  extremes,  178. 

Tendons,  439. 

Tensor  tympani,  365. 

Tenth  pair  of  nerves,  340. 

Testis,  516;  secretion  of,  517. 

Thackrah  on  effect  of  want,  587. 

Thenard  on  perspiration,  240. 

Third  pair  of  nerves,  333. 

Thoracic  duct,  90. 

Tickling,  422. 

Tidal  air,  165. 

Time,  introduction  of,  into  nervous  mecha- 
nism, 269,  287. 

Tin,  trade  in,  619. 

TISSUE,  cellular,  497;  mnriform,  497 ;  fibro- 
cellular,  497;  vascular,  498 ;  yellow  fibrous, 
499 ;  white  fibrous,  499 ;  areolar,  499. 

Tongue,  428. 

TOUCH,  structure  of  organ  of,  417, 418 ;  acute- 
ness  of,  420;  in  animals,  421 ;  connected 
with  vision,  419. 

Tournefort  on  plants,  472. 

Toynbee  on  ear,  365. 

Tracts  of  spinal  cord,  303 ;  of  brain,  318. 

Tradescantia  Virginica,  circulation  in,  132. 

Traditions,  567. 

Trains  of  thought,  329. 

Transverse  transmission  in  spinal  cord,  298. 

Trembley  on  hydra,  501. 

Trigemini,  334. 

Trisplanchnic  nerve,  344. 

Turner  on  smell,  427. 

Twelfth  pair,  343. 

Twins,  similarity  of,  509. 

Tympanum,  360,  365. 

Type,  ideal,  of  man,  565,  611. 

U. 

UNIPOLAR  NERVE-CELLS,  263,  268. 
Universal  history,  611. 
Urea,  447. 

URINE,  218  ;  composition  of,  219 ;  urea  con- 
tained in  it,  220 ;  hippuric  acid  in,  222 ; 


INDEX. 


649 


variability  of,  219  ;  sulphates  in,  220;  in- 
fluence of  diet  on,  220 ;  saline  matter  of, 
220. 

Uterine  nutrition,  525 ;  tubes,  525. 

Utricle,  416. 

V. 

VACUUM,  tendency  to  a,  in  respiration,  165. 
Valentin  on  diffusion,  163 ;  on  perspiration, 

229  ;  on  food,  39. 

Valves  of  the  heart,  138 ;  sounds  of,  139. 
Valvulae  conniventes,  67. 
Variable  results  from  invariable  causes,  270, 

281. 
Variations  of  heat,  179 ;  effect  of,  on  man, 

180 ;  of  species  of  plants,  479. 
VASCULAR  area,  528  ;  lamina,  528  ;  system, 

origin  of,  528. 

Vegetable  cells,  circulation  in,  132,  466. 
Veins,  absorption  by,  84,  143. 
Ventral  cord,  300,  307,  609. 
Ventricles,  138 ;  force  of,  139. 
Venturi,  principle  of,  90. 
Vermiform  appendix,  63. 
Vernois,  table  from,  53. 
Vertebra,  528. 
Vertebral  canal,  294. 
Vertebrata,  294. 
Vertical  view  of  skull,  582. 
VESICULAR  matter,  composition  of,  274 ;  re- 
lations of,  315. 
Vestibule,  374. 

Vestiges  of  nervous  impressions,  269,  288. 
Vibration  of  sound,  time  measured  by,  372. 
Vicarious  action,  47,  190. 
Vierordt,  164. 
Villi,  84,  86,  87, 110 ;  cells  of,  88 ;  action  of, 

110. 

Virchow  on  adipocire,  247. 
VISION,  379 ;  comparative  anatomy  of,  380 ; 

single  and  double,  395 ;  inverse,  401. 
Visions,  404  ;  conditions  of,  410. 
Visual  hallucinations,  403. 
Vital  principle,  24,  25,  55, 108,  456. 
Vital  spark,  460. 
Vitreous  humor,  385. 
Vocal  sounds,  352,  354. 
Voice,  351 ;  artificial  larynx,  355 ;  pitch  of, 

356. 


Volkmann  on  muscular  contraction,  276. 

Volume  of  contracting  muscle,  450. 

Volvox  globator,  513. 

Von  Bar,  law  of,  514. 

Von  Becker  on  carbohydrates,  39 ;  on  sugar, 

73. 
Vowels,  356. 


W. 


WALKING,  453. 

Wallace  on  eye,  385. 

Want,  effect  of,  587. 

Warmth,  artificial,  181 ;  increased  quantity 

required  in  sleep,  554. 
Wasmann  on  pepsin,  55. 
Wasp,  habits  of,  606. 
Waste  of  tissue,  12,  23,  52. 
WATER,  use  of,  16,  21,  22 ;  solvent  power  of, 

21 ;  use  in  milk,  29  ;   absorption  of,  52  ; 

quantity  exhaled,  168  j  cooling  effect  of, 

185;  of  blood,  121. 
Wave  in  blood,  141. 
Weaning  of  plants,  465. 
Weber  on  pelvis,  587  ;  on  quantity  of  blood, 

113 ;  on  standing,  453. 
Weight  of  man,  13,  14,  541 ;  of  infants,  14. 
Whale,  491. 
Wheatstone,  397. 
Whispering,  356. 
White  on  arm,  580. 
Wigan  on  duality  of  mind,  329,  331. 
Willow,  469. 
Wilson  on  heart,  136. 
Wine-making,  78. 
Wolffian  bodies,  150,  533. 
Women  in  Asia  and  Europe,  593. 
Words,  origin  of,  356. 
Worship,  public,  influence  of,  628. 
Writing,  358,  610,  615,  635. 


ZIGZAG  appearance  of  muscle,  439. 
Zimmerman  on  respiration,  170. 
Zinc  acted  on  by  gastric  juice,  50. 
Zona  pellucida,  523,  525. 
Zoospores,  496. 
Zygnema  quininum,  515. 


THE  END. 


Harper's  Catalogue. 


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